Manual Pages for UNIX Operating System command usage for man zshexpn
User Commands ZSHEXPN(1)
NAME
zshexpn - zsh expansion and substitution
DESCRIPTION
The following types of expansions are performed in the indi-
cated order in five steps:
History Expansion
This is performed only in interactive shells.
Alias Expansion
Aliases are expanded immediately before the command
line is parsed as explained under Aliasing in
zshmisc(1).
Process Substitution
Parameter Expansion
Command Substitution
Arithmetic Expansion
Brace Expansion
These five are performed in one step in left-to-right
fashion. After these expansions, all unquoted
occurrences of the characters `\', `'' and `"' are
removed.
Filename Expansion
If the SH_FILE_EXPANSION option is set, the order of
expansion is modified for compatibility with sh and
ksh. In that case filename expansion is performed
immediately after alias expansion, preceding the set of
five expansions mentioned above.
Filename Generation
This expansion, commonly referred to as globbing, is
always done last.
The following sections explain the types of expansion in
detail.
HISTORY EXPANSION
History expansion allows you to use words from previous com-
mand lines in the command line you are typing. This simpli-
fies spelling corrections and the repetition of complicated
commands or arguments. Immediately before execution, each
command is saved in the history list, the size of which is
controlled by the HISTSIZE parameter. The one most recent
command is always retained in any case. Each saved command
in the history list is called a history event and is
assigned a number, beginning with 1 (one) when the shell
starts up. The history number that you may see in your
prompt (see EXPANSION OF PROMPT SEQUENCES in zshmisc(1)) is
the number that is to be assigned to the next command.
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Overview
A history expansion begins with the first character of the
histchars parameter, which is `!' by default, and may occur
anywhere on the command line; history expansions do not
nest. The `!' can be escaped with `\' or can be enclosed
between a pair of single quotes ('') to suppress its special
meaning. Double quotes will not work for this. Following
this history character is an optional event designator (see
the section `Event Designators') and then an optional word
designator (the section `Word Designators'); if neither of
these designators is present, no history expansion occurs.
Input lines containing history expansions are echoed after
being expanded, but before any other expansions take place
and before the command is executed. It is this expanded
form that is recorded as the history event for later refer-
ences.
By default, a history reference with no event designator
refers to the same event as any preceding history reference
on that command line; if it is the only history reference in
a command, it refers to the previous command. However, if
the option CSH_JUNKIE_HISTORY is set, then every history
reference with no event specification always refers to the
previous command.
For example, `!' is the event designator for the previous
command, so `!!:1' always refers to the first word of the
previous command, and `!!$' always refers to the last word
of the previous command. With CSH_JUNKIE_HISTORY set, then
`!:1' and `!$' function in the same manner as `!!:1' and
`!!$', respectively. Conversely, if CSH_JUNKIE_HISTORY is
unset, then `!:1' and `!$' refer to the first and last
words, respectively, of the same event referenced by the
nearest other history reference preceding them on the
current command line, or to the previous command if there is
no preceding reference.
The character sequence `^foo^bar' (where `^' is actually the
second character of the histchars parameter) repeats the
last command, replacing the string foo with bar. More pre-
cisely, the sequence `^foo^bar^' is synonymous with
`!!:s^foo^bar^', hence other modifiers (see the section
`Modifiers') may follow the final `^'. In particular,
`^foo^bar:G' performs a global substitution.
If the shell encounters the character sequence `!"' in the
input, the history mechanism is temporarily disabled until
the current list (see zshmisc(1)) is fully parsed. The `!"'
is removed from the input, and any subsequent `!' characters
have no special significance.
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A less convenient but more comprehensible form of command
history support is provided by the fc builtin.
Event Designators
An event designator is a reference to a command-line entry
in the history list. In the list below, remember that the
initial `!' in each item may be changed to another character
by setting the histchars parameter.
! Start a history expansion, except when followed by a
blank, newline, `=' or `('. If followed immediately by
a word designator (see the section `Word Designators'),
this forms a history reference with no event designator
(see the section `Overview').
!! Refer to the previous command. By itself, this expan-
sion repeats the previous command.
!n Refer to command-line n.
!-n Refer to the current command-line minus n.
!str Refer to the most recent command starting with str.
!?str[?]
Refer to the most recent command containing str. The
trailing `?' is necessary if this reference is to be
followed by a modifier or followed by any text that is
not to be considered part of str.
!# Refer to the current command line typed in so far. The
line is treated as if it were complete up to and
including the word before the one with the `!#' refer-
ence.
!{...}
Insulate a history reference from adjacent characters
(if necessary).
Word Designators
A word designator indicates which word or words of a given
command line are to be included in a history reference. A
`:' usually separates the event specification from the word
designator. It may be omitted only if the word designator
begins with a `^', `$', `*', `-' or `%'. Word designators
include:
0 The first input word (command).
n The nth argument.
^ The first argument. That is, 1.
$ The last argument.
% The word matched by (the most recent) ?str search.
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x-y A range of words; x defaults to 0.
* All the arguments, or a null value if there are none.
x* Abbreviates `x-$'.
x- Like `x*' but omitting word $.
Note that a `%' word designator works only when used in one
of `!%', `!:%' or `!?str?:%', and only when used after a !?
expansion (possibly in an earlier command). Anything else
results in an error, although the error may not be the most
obvious one.
Modifiers
After the optional word designator, you can add a sequence
of one or more of the following modifiers, each preceded by
a `:'. These modifiers also work on the result of filename
generation and parameter expansion, except where noted.
a Turn a file name into an absolute path: prepends the
current directory, if necessary, and resolves any use
of `..' and `.' in the path. Note that the transforma-
tion takes place even if the file or any intervening
directories do not exist.
A As `a', but also resolve use of symbolic links where
possible. Note that resolution of `..' occurs before
resolution of symbolic links. This call is equivalent
to a unless your system has the realpath system call
(modern systems do).
c Resolve a command name into an absolute path by search-
ing the command path given by the PATH variable. This
does not work for commands containing directory parts.
Note also that this does not usually work as a glob
qualifier unless a file of the same name is found in
the current directory.
e Remove all but the extension.
h Remove a trailing pathname component, leaving the head.
This works like `dirname'.
l Convert the words to all lowercase.
p Print the new command but do not execute it. Only
works with history expansion.
q Quote the substituted words, escaping further substitu-
tions. Works with history expansion and parameter
expansion, though for parameters it is only useful if
the resulting text is to be re-evaluated such as by
eval.
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Q Remove one level of quotes from the substituted words.
r Remove a filename extension of the form `.xxx', leaving
the root name.
s/l/r[/]
Substitute r for l as described below. The substitu-
tion is done only for the first string that matches l.
For arrays and for filename generation, this applies to
each word of the expanded text. See below for further
notes on substitutions.
The forms `gs/l/r' and `s/l/r/:G' perform global sub-
stitution, i.e. substitute every occurrence of r for l.
Note that the g or :G must appear in exactly the posi-
tion shown.
& Repeat the previous s substitution. Like s, may be
preceded immediately by a g. In parameter expansion
the & must appear inside braces, and in filename gen-
eration it must be quoted with a backslash.
t Remove all leading pathname components, leaving the
tail. This works like `basename'.
u Convert the words to all uppercase.
x Like q, but break into words at whitespace. Does not
work with parameter expansion.
The s/l/r/ substitution works as follows. By default the
left-hand side of substitutions are not patterns, but char-
acter strings. Any character can be used as the delimiter
in place of `/'. A backslash quotes the delimiter charac-
ter. The character `&', in the right-hand-side r, is
replaced by the text from the left-hand-side l. The `&' can
be quoted with a backslash. A null l uses the previous
string either from the previous l or from the contextual
scan string s from `!?s'. You can omit the rightmost delim-
iter if a newline immediately follows r; the rightmost `?'
in a context scan can similarly be omitted. Note the same
record of the last l and r is maintained across all forms of
expansion.
If the option HIST_SUBST_PATTERN is set, l is treated as a
pattern of the usual form described in the section FILENAME
GENERATION below. This can be used in all the places where
modifiers are available; note, however, that in globbing
qualifiers parameter substitution has already taken place,
so parameters in the replacement string should be quoted to
ensure they are replaced at the correct time. Note also
that complicated patterns used in globbing qualifiers may
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need the extended glob qualifier notation (#q:s/.../.../) in
order for the shell to recognize the expression as a glob
qualifier. Further, note that bad patterns in the substitu-
tion are not subject to the NO_BAD_PATTERN option so will
cause an error.
When HIST_SUBST_PATTERN is set, l may start with a # to
indicate that the pattern must match at the start of the
string to be substituted, and a % may appear at the start or
after an # to indicate that the pattern must match at the
end of the string to be substituted. The % or # may be
quoted with two backslashes.
For example, the following piece of filename generation code
with the EXTENDED_GLOB option:
print *.c(#q:s/#%(#b)s(*).c/'S${match[1]}.C'/)
takes the expansion of *.c and applies the glob qualifiers
in the (#q...) expression, which consists of a substitution
modifier anchored to the start and end of each word (#%).
This turns on backreferences ((#b)), so that the
parenthesised subexpression is available in the replacement
string as ${match[1]}. The replacement string is quoted so
that the parameter is not substituted before the start of
filename generation.
The following f, F, w and W modifiers work only with parame-
ter expansion and filename generation. They are listed here
to provide a single point of reference for all modifiers.
f Repeats the immediately (without a colon) following
modifier until the resulting word doesn't change any
more.
F:expr:
Like f, but repeats only n times if the expression expr
evaluates to n. Any character can be used instead of
the `:'; if `(', `[', or `{' is used as the opening
delimiter, the closing delimiter should be ')', `]', or
`}', respectively.
w Makes the immediately following modifier work on each
word in the string.
W:sep:
Like w but words are considered to be the parts of the
string that are separated by sep. Any character can be
used instead of the `:'; opening parentheses are han-
dled specially, see above.
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PROCESS SUBSTITUTION
Each part of a command argument that takes the form
`<(list)', `>(list)' or `=(list)' is subject to process sub-
stitution. The expression may be preceeded or followed by
other strings except that, to prevent clashes with commonly
occurring strings and patterns, the last form must occur at
the start of a command argument, and the forms are only
expanded when first parsing command or assignment arguments.
Process substitutions may be used following redirection
operators; in this case, the substitution must appear with
no trailing string.
In the case of the < or > forms, the shell runs the commands
in list asynchronously. If the system supports the /dev/fd
mechanism, the command argument is the name of the device
file corresponding to a file descriptor; otherwise, if the
system supports named pipes (FIFOs), the command argument
will be a named pipe. If the form with > is selected then
writing on this special file will provide input for list.
If < is used, then the file passed as an argument will be
connected to the output of the list process. For example,
paste <(cut -f1 file1) <(cut -f3 file2) |
tee >(process1) >(process2) >/dev/null
cuts fields 1 and 3 from the files file1 and file2 respec-
tively, pastes the results together, and sends it to the
processes process1 and process2.
If =(...) is used instead of <(...), then the file passed as
an argument will be the name of a temporary file containing
the output of the list process. This may be used instead of
the < form for a program that expects to lseek (see
lseek(2)) on the input file.
There is an optimisation for substitutions of the form
=(<< here-string redirection <<<. This form produces a file name
containing the value of arg after any substitutions have
been performed. This is handled entirely within the current
shell. This is effectively the reverse of the special form
$( the file's contents.
The = form is useful as both the /dev/fd and the named pipe
implementation of <(...) have drawbacks. In the former
case, some programmes may automatically close the file
descriptor in question before examining the file on the com-
mand line, particularly if this is necessary for security
reasons such as when the programme is running setuid. In
the second case, if the programme does not actually open the
file, the subshell attempting to read from or write to the
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pipe will (in a typical implementation, different operating
systems may have different behaviour) block for ever and
have to be killed explicitly. In both cases, the shell
actually supplies the information using a pipe, so that pro-
grammes that expect to lseek (see lseek(2)) on the file will
not work.
Also note that the previous example can be more compactly
and efficiently written (provided the MULTIOS option is set)
as:
paste <(cut -f1 file1) <(cut -f3 file2) \
> >(process1) > >(process2)
The shell uses pipes instead of FIFOs to implement the
latter two process substitutions in the above example.
There is an additional problem with >(process); when this is
attached to an external command, the parent shell does not
wait for process to finish and hence an immediately follow-
ing command cannot rely on the results being complete. The
problem and solution are the same as described in the sec-
tion MULTIOS in zshmisc(1). Hence in a simplified version
of the example above:
paste <(cut -f1 file1) <(cut -f3 file2) > >(process)
(note that no MULTIOS are involved), process will be run
asynchronously. The workaround is:
{ paste <(cut -f1 file1) <(cut -f3 file2) } > >(process)
The extra processes here are spawned from the parent shell
which will wait for their completion.
PARAMETER EXPANSION
The character `$' is used to introduce parameter expansions.
See zshparam(1) for a description of parameters, including
arrays, associative arrays, and subscript notation to access
individual array elements.
Note in particular the fact that words of unquoted parame-
ters are not automatically split on whitespace unless the
option SH_WORD_SPLIT is set; see references to this option
below for more details. This is an important difference
from other shells.
In the expansions discussed below that require a pattern,
the form of the pattern is the same as that used for
filename generation; see the section `Filename Generation'.
Note that these patterns, along with the replacement text of
any substitutions, are themselves subject to parameter
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expansion, command substitution, and arithmetic expansion.
In addition to the following operations, the colon modifiers
described in the section `Modifiers' in the section `History
Expansion' can be applied: for example, ${i:s/foo/bar/}
performs string substitution on the expansion of parameter
$i.
${name}
The value, if any, of the parameter name is substi-
tuted. The braces are required if the expansion is to
be followed by a letter, digit, or underscore that is
not to be interpreted as part of name. In addition,
more complicated forms of substitution usually require
the braces to be present; exceptions, which only apply
if the option KSH_ARRAYS is not set, are a single sub-
script or any colon modifiers appearing after the name,
or any of the characters `^', `=', `~', `#' or `+'
appearing before the name, all of which work with or
without braces.
If name is an array parameter, and the KSH_ARRAYS
option is not set, then the value of each element of
name is substituted, one element per word. Otherwise,
the expansion results in one word only; with
KSH_ARRAYS, this is the first element of an array. No
field splitting is done on the result unless the
SH_WORD_SPLIT option is set. See also the flags = and
s:string:.
${+name}
If name is the name of a set parameter `1' is substi-
tuted, otherwise `0' is substituted.
${name-word}
${name:-word}
If name is set, or in the second form is non-null, then
substitute its value; otherwise substitute word. In
the second form name may be omitted, in which case word
is always substituted.
${name+word}
${name:+word}
If name is set, or in the second form is non-null, then
substitute word; otherwise substitute nothing.
${name=word}
${name:=word}
${name::=word}
In the first form, if name is unset then set it to
word; in the second form, if name is unset or null then
set it to word; and in the third form, unconditionally
set name to word. In all forms, the value of the
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parameter is then substituted.
${name?word}
${name:?word}
In the first form, if name is set, or in the second
form if name is both set and non-null, then substitute
its value; otherwise, print word and exit from the
shell. Interactive shells instead return to the
prompt. If word is omitted, then a standard message is
printed.
In any of the above expressions that test a variable and
substitute an alternate word, note that you can use standard
shell quoting in the word value to selectively override the
splitting done by the SH_WORD_SPLIT option and the = flag,
but not splitting by the s:string: flag.
In the following expressions, when name is an array and the
substitution is not quoted, or if the `(@)' flag or the
name[@] syntax is used, matching and replacement is per-
formed on each array element separately.
${name#pattern}
${name##pattern}
If the pattern matches the beginning of the value of
name, then substitute the value of name with the
matched portion deleted; otherwise, just substitute the
value of name. In the first form, the smallest match-
ing pattern is preferred; in the second form, the larg-
est matching pattern is preferred.
${name%pattern}
${name%%pattern}
If the pattern matches the end of the value of name,
then substitute the value of name with the matched por-
tion deleted; otherwise, just substitute the value of
name. In the first form, the smallest matching pattern
is preferred; in the second form, the largest matching
pattern is preferred.
${name:#pattern}
If the pattern matches the value of name, then substi-
tute the empty string; otherwise, just substitute the
value of name. If name is an array the matching array
elements are removed (use the `(M)' flag to remove the
non-matched elements).
${name/pattern/repl}
${name//pattern/repl}
Replace the longest possible match of pattern in the
expansion of parameter name by string repl. The first
form replaces just the first occurrence, the second
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form all occurrences. Both pattern and repl are sub-
ject to double-quoted substitution, so that expressions
like ${name/$opat/$npat} will work, but note the usual
rule that pattern characters in $opat are not treated
specially unless either the option GLOB_SUBST is set,
or $opat is instead substituted as ${~opat}.
The pattern may begin with a `#', in which case the
pattern must match at the start of the string, or `%',
in which case it must match at the end of the string,
or `#%' in which case the pattern must match the entire
string. The repl may be an empty string, in which case
the final `/' may also be omitted. To quote the final
`/' in other cases it should be preceded by a single
backslash; this is not necessary if the `/' occurs
inside a substituted parameter. Note also that the
`#', `%' and `#% are not active if they occur inside a
substituted parameter, even at the start.
The first `/' may be preceded by a `:', in which case
the match will only succeed if it matches the entire
word. Note also the effect of the I and S parameter
expansion flags below; however, the flags M, R, B, E
and N are not useful.
For example,
foo="twinkle twinkle little star" sub="t*e" rep="spy"
print ${foo//${~sub}/$rep}
print ${(S)foo//${~sub}/$rep}
Here, the `~' ensures that the text of $sub is treated
as a pattern rather than a plain string. In the first
case, the longest match for t*e is substituted and the
result is `spy star', while in the second case, the
shortest matches are taken and the result is `spy spy
lispy star'.
${#spec}
If spec is one of the above substitutions, substitute
the length in characters of the result instead of the
result itself. If spec is an array expression, substi-
tute the number of elements of the result. Note that
`^', `=', and `~', below, must appear to the left of
`#' when these forms are combined.
${^spec}
Turn on the RC_EXPAND_PARAM option for the evaluation
of spec; if the `^' is doubled, turn it off. When this
option is set, array expansions of the form
foo${xx}bar, where the parameter xx is set to (a b c),
are substituted with `fooabar foobbar foocbar' instead
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of the default `fooa b cbar'. Note that an empty array
will therefore cause all arguments to be removed.
Internally, each such expansion is converted into the
equivalent list for brace expansion. E.g., ${^var}
becomes {$var[1],$var[2],...}, and is processed as
described in the section `Brace Expansion' below. If
word splitting is also in effect the $var[N] may them-
selves be split into different list elements.
${=spec}
Perform word splitting using the rules for
SH_WORD_SPLIT during the evaluation of spec, but
regardless of whether the parameter appears in double
quotes; if the `=' is doubled, turn it off. This
forces parameter expansions to be split into separate
words before substitution, using IFS as a delimiter.
This is done by default in most other shells.
Note that splitting is applied to word in the assign-
ment forms of spec before the assignment to name is
performed. This affects the result of array assign-
ments with the A flag.
${~spec}
Turn on the GLOB_SUBST option for the evaluation of
spec; if the `~' is doubled, turn it off. When this
option is set, the string resulting from the expansion
will be interpreted as a pattern anywhere that is pos-
sible, such as in filename expansion and filename gen-
eration and pattern-matching contexts like the right
hand side of the `=' and `!=' operators in conditions.
In nested substitutions, note that the effect of the ~
applies to the result of the current level of substitu-
tion. A surrounding pattern operation on the result
may cancel it. Hence, for example, if the parameter
foo is set to *, ${~foo//\*/*.c} is substituted by the
pattern *.c, which may be expanded by filename genera-
tion, but ${${~foo}//\*/*.c} substitutes to the string
*.c, which will not be further expanded.
If a ${...} type parameter expression or a $(...) type com-
mand substitution is used in place of name above, it is
expanded first and the result is used as if it were the
value of name. Thus it is possible to perform nested opera-
tions: ${${foo#head}%tail} substitutes the value of $foo
with both `head' and `tail' deleted. The form with $(...)
is often useful in combination with the flags described
next; see the examples below. Each name or nested ${...} in
a parameter expansion may also be followed by a subscript
expression as described in Array Parameters in zshparam(1).
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Note that double quotes may appear around nested expres-
sions, in which case only the part inside is treated as
quoted; for example, ${(f)"$(foo)"} quotes the result of
$(foo), but the flag `(f)' (see below) is applied using the
rules for unquoted expansions. Note further that quotes are
themselves nested in this context; for example, in
"${(@f)"$(foo)"}", there are two sets of quotes, one sur-
rounding the whole expression, the other (redundant) sur-
rounding the $(foo) as before.
Parameter Expansion Flags
If the opening brace is directly followed by an opening
parenthesis, the string up to the matching closing
parenthesis will be taken as a list of flags. In cases
where repeating a flag is meaningful, the repetitions need
not be consecutive; for example, `(q%q%q)' means the same
thing as the more readable `(%%qqq)'. The following flags
are supported:
# Evaluate the resulting words as numeric expressions and
output the characters corresponding to the resulting
integer. Note that this form is entirely distinct from
use of the # without parentheses.
If the MULTIBYTE option is set and the number is
greater than 127 (i.e. not an ASCII character) it is
treated as a Unicode character.
% Expand all % escapes in the resulting words in the same
way as in prompts (see EXPANSION OF PROMPT SEQUENCES in
zshmisc(1)). If this flag is given twice, full prompt
expansion is done on the resulting words, depending on
the setting of the PROMPT_PERCENT, PROMPT_SUBST and
PROMPT_BANG options.
@ In double quotes, array elements are put into separate
words. E.g., `"${(@)foo}"' is equivalent to
`"${foo[@]}"' and `"${(@)foo[1,2]}"' is the same as
`"$foo[1]" "$foo[2]"'. This is distinct from field
splitting by the the f, s or z flags, which still
applies within each array element.
A Create an array parameter with `${...=...}',
`${...:=...}' or `${...::=...}'. If this flag is
repeated (as in `AA'), create an associative array
parameter. Assignment is made before sorting or pad-
ding. The name part may be a subscripted range for
ordinary arrays; the word part must be converted to an
array, for example by using `${(AA)=name=...}' to
activate field splitting, when creating an associative
array.
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a Sort in array index order; when combined with `O' sort
in reverse array index order. Note that `a' is there-
fore equivalent to the default but `Oa' is useful for
obtaining an array's elements in reverse order.
c With ${#name}, count the total number of characters in
an array, as if the elements were concatenated with
spaces between them.
C Capitalize the resulting words. `Words' in this case
refers to sequences of alphanumeric characters
separated by non-alphanumerics, not to words that
result from field splitting.
e Perform parameter expansion, command substitution and
arithmetic expansion on the result. Such expansions can
be nested but too deep recursion may have unpredictable
effects.
f Split the result of the expansion to lines. This is a
shorthand for `ps:\n:'.
F Join the words of arrays together using newline as a
separator. This is a shorthand for `pj:\n:'.
i Sort case-insensitively. May be combined with `n' or
`O'.
k If name refers to an associative array, substitute the
keys (element names) rather than the values of the ele-
ments. Used with subscripts (including ordinary
arrays), force indices or keys to be substituted even
if the subscript form refers to values. However, this
flag may not be combined with subscript ranges.
L Convert all letters in the result to lower case.
n Sort decimal integers numerically; if the first differ-
ing characters of two test strings are not digits,
sorting is lexical. Integers with more initial zeroes
are sorted before those with fewer or none. Hence the
array `foo1 foo02 foo2 foo3 foo20 foo23' is sorted into
the order shown. May be combined with `i' or `O'.
o Sort the resulting words in ascending order; if this
appears on its own the sorting is lexical and
case-sensitive (unless the locale renders it
case-insensitive). Sorting in ascending order is the
default for other forms of sorting, so this is ignored
if combined with `a', `i' or `n'.
O Sort the resulting words in descending order; `O'
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without `a', `i' or `n' sorts in reverse lexical order.
May be combined with `a', `i' or `n' to reverse the
order of sorting.
P This forces the value of the parameter name to be
interpreted as a further parameter name, whose value
will be used where appropriate. Note that flags set
with one of the typeset family of commands (in particu-
lar case transformations) are not applied to the value
of name used in this fashion.
If used with a nested parameter or command substitu-
tion, the result of that will be taken as a parameter
name in the same way. For example, if you have
`foo=bar' and `bar=baz', the strings ${(P)foo},
${(P)${foo}}, and ${(P)$(echo bar)} will be expanded to
`baz'.
q Quote the resulting words with backslashes; unprintable
or invalid characters are quoted using the $'\NNN'
form, with separate quotes for each octet. If this
flag is given twice, the resulting words are quoted in
single quotes and if it is given three times, the words
are quoted in double quotes; in these forms no special
handling of unprintable or invalid characters is
attempted. If the flag is given four times, the words
are quoted in single quotes preceded by a $.
Q Remove one level of quotes from the resulting words.
t Use a string describing the type of the parameter where
the value of the parameter would usually appear. This
string consists of keywords separated by hyphens (`-').
The first keyword in the string describes the main
type, it can be one of `scalar', `array', `integer',
`float' or `association'. The other keywords describe
the type in more detail:
local
for local parameters
left for left justified parameters
right_blanks
for right justified parameters with leading blanks
right_zeros
for right justified parameters with leading zeros
lower
for parameters whose value is converted to all
lower case when it is expanded
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upper
for parameters whose value is converted to all
upper case when it is expanded
readonly
for readonly parameters
tag for tagged parameters
export
for exported parameters
unique
for arrays which keep only the first occurrence of
duplicated values
hide for parameters with the `hide' flag
special
for special parameters defined by the shell
u Expand only the first occurrence of each unique word.
U Convert all letters in the result to upper case.
v Used with k, substitute (as two consecutive words) both
the key and the value of each associative array ele-
ment. Used with subscripts, force values to be substi-
tuted even if the subscript form refers to indices or
keys.
V Make any special characters in the resulting words
visible.
w With ${#name}, count words in arrays or strings; the s
flag may be used to set a word delimiter.
W Similar to w with the difference that empty words
between repeated delimiters are also counted.
X With this flag, parsing errors occurring with the Q, e
and # flags or the pattern matching forms such as
`${name#pattern}' are reported. Without the flag,
errors are silently ignored.
z Split the result of the expansion into words using
shell parsing to find the words, i.e. taking into
account any quoting in the value.
Note that this is done very late, as for the `(s)'
flag. So to access single words in the result, one has
to use nested expansions as in `${${(z)foo}[2]}'.
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Likewise, to remove the quotes in the resulting words
one would do: `${(Q)${(z)foo}}'.
0 Split the result of the expansion on null bytes. This
is a shorthand for `ps:\0:'.
The following flags (except p) are followed by one or more
arguments as shown. Any character, or the matching pairs
`(...)', `{...}', `[...]', or `<...>', may be used in place
of a colon as delimiters, but note that when a flag takes
more than one argument, a matched pair of delimiters must
surround each argument.
p Recognize the same escape sequences as the print buil-
tin in string arguments to any of the flags described
below that follow this argument.
~ Force string arguments to any of the flags below that
follow within the parentheses to be treated as pat-
terns. Compare with a ~ outside parentheses, which
forces the entire substituted string to be treated as a
pattern. Hence, for example,
[[ "?" = ${(~j.|.)array} ]]
with the EXTENDED_GLOB option set succeeds if and only if
$array contains the string `?' as an element. The argument
may be repeated to toggle the behaviour; its effect only
lasts to the end of the parenthesised group.
j:string:
Join the words of arrays together using string as a
separator. Note that this occurs before field split-
ting by the s:string: flag or the SH_WORD_SPLIT
option.
l:expr::string1::string2:
Pad the resulting words on the left. Each word will be
truncated if required and placed in a field expr char-
acters wide.
The arguments :string1: and :string2: are optional;
neither, the first, or both may be given. Note that
the same pairs of delimiters must be used for each of
the three arguments. The space to the left will be
filled with string1 (concatenated as often as needed)
or spaces if string1 is not given. If both string1 and
string2 are given, string2 is inserted once directly to
the left of each word, truncated if necessary, before
string1 is used to produce any remaining padding.
If the MULTIBYTE option is in effect, the flag m may
also be given, in which case widths will be used for
the calculation of padding; otherwise individual
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multibyte characters are treated as occupying one unit
of width.
IF the MULTIBYTE option is not in effect, each byte in
the string is treated as occupying one unit of width.
Control characters are always assumed to be one unit
wide; this allows the mechanism to be used for generat-
ing repetitions of control characters.
m Only useful together with one of the flags l or r or
with the # length operator when the MULTIBYTE option is
in effect. Use the character width reported by the
system in calculating the how much of the string it
occupies or the overall length of the string. Most
printable characters have a width of one unit, however
certain Asian character sets and certain special
effects use wider characters; combining characters have
zero width.
r:expr::string1::string2:
As l, but pad the words on the right and insert string2
immediately to the right of the string to be padded.
Left and right padding may be used together. In this
case the strategy is to apply left padding to the first
half width of each of the resulting words, and right
padding to the second half. If the string to be padded
has odd width the extra padding is applied on the left.
s:string:
Force field splitting at the separator string. Note
that a string of two or more characters means that all
of them must match in sequence; this differs from the
treatment of two or more characters in the IFS parame-
ter. See also the = flag and the SH_WORD_SPLIT option.
For historical reasons, the usual behaviour that empty
array elements are retained inside double quotes is
disabled for arrays generated by splitting; hence the
following:
line="one::three"
print -l "${(s.:.)line}"
produces two lines of output for one and three and
elides the empty field. To override this behaviour,
supply the "(@)" flag as well, i.e. "${(@s.:.)line}".
The following flags are meaningful with the ${...#...} or
${...%...} forms. The S and I flags may also be used with
the ${.../...} forms.
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S Search substrings as well as beginnings or ends; with #
start from the beginning and with % start from the end
of the string. With substitution via ${.../...} or
${...//...}, specifies non-greedy matching, i.e. that
the shortest instead of the longest match should be
replaced.
I:expr:
Search the exprth match (where expr evaluates to a
number). This only applies when searching for sub-
strings, either with the S flag, or with ${.../...}
(only the exprth match is substituted) or ${...//...}
(all matches from the exprth on are substituted). The
default is to take the first match.
The exprth match is counted such that there is either
one or zero matches from each starting position in the
string, although for global substitution matches over-
lapping previous replacements are ignored. With the
${...%...} and ${...%%...} forms, the starting position
for the match moves backwards from the end as the index
increases, while with the other forms it moves forward
from the start.
Hence with the string
which switch is the right switch for Ipswich?
substitutions of the form ${(SI:N:)string#w*ch} as N
increases from 1 will match and remove `which',
`witch', `witch' and `wich'; the form using `##' will
match and remove `which switch is the right switch for
Ipswich', `witch is the right switch for Ipswich',
`witch for Ipswich' and `wich'. The form using `%' will
remove the same matches as for `#', but in reverse
order, and the form using `%%' will remove the same
matches as for `##' in reverse order.
B Include the index of the beginning of the match in the
result.
E Include the index of the end of the match in the
result.
M Include the matched portion in the result.
N Include the length of the match in the result.
R Include the unmatched portion in the result (the Rest).
Rules
Here is a summary of the rules for substitution; this
assumes that braces are present around the substitution,
i.e. ${...}. Some particular examples are given below.
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Note that the Zsh Development Group accepts no responsibil-
ity for any brain damage which may occur during the reading
of the following rules.
1. Nested Substitution
If multiple nested ${...} forms are present, substitu-
tion is performed from the inside outwards. At each
level, the substitution takes account of whether the
current value is a scalar or an array, whether the
whole substitution is in double quotes, and what flags
are supplied to the current level of substitution, just
as if the nested substitution were the outermost. The
flags are not propagated up to enclosing substitutions;
the nested substitution will return either a scalar or
an array as determined by the flags, possibly adjusted
for quoting. All the following steps take place where
applicable at all levels of substitution. Note that,
unless the `(P)' flag is present, the flags and any
subscripts apply directly to the value of the nested
substitution; for example, the expansion ${${foo}}
behaves exactly the same as ${foo}.
At each nested level of substitution, the substituted
words undergo all forms of single-word substitution
(i.e. not filename generation), including command sub-
stitution, arithmetic expansion and filename expansion
(i.e. leading ~ and =). Thus, for example,
${${:-=cat}:h} expands to the directory where the cat
program resides. (Explanation: the internal substitu-
tion has no parameter but a default value =cat, which
is expanded by filename expansion to a full path; the
outer substitution then applies the modifier :h and
takes the directory part of the path.)
2. Internal Parameter Flags
Any parameter flags set by one of the typeset family of
commands, in particular the L, R, Z, u and l flags for
padding and capitalization, are applied directly to the
parameter value.
3. Parameter Subscripting
If the value is a raw parameter reference with a sub-
script, such as ${var[3]}, the effect of subscripting
is applied directly to the parameter. Subscripts are
evaluated left to right; subsequent subscripts apply to
the scalar or array value yielded by the previous sub-
script. Thus if var is an array, ${var[1][2]} is the
second character of the first word, but ${var[2,4][2]}
is the entire third word (the second word of the range
of words two through four of the original array). Any
number of subscripts may appear.
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4. Parameter Name Replacement
The effect of any (P) flag, which treats the value so
far as a parameter name and replaces it with the
corresponding value, is applied.
5. Double-Quoted Joining
If the value after this process is an array, and the
substitution appears in double quotes, and no (@) flag
is present at the current level, the words of the value
are joined with the first character of the parameter
$IFS, by default a space, between each word (single
word arrays are not modified). If the (j) flag is
present, that is used for joining instead of $IFS.
6. Nested Subscripting
Any remaining subscripts (i.e. of a nested substitu-
tion) are evaluated at this point, based on whether the
value is an array or a scalar. As with 2., multiple
subscripts can appear. Note that ${foo[2,4][2]} is
thus equivalent to ${${foo[2,4]}[2]} and also to
"${${(@)foo[2,4]}[2]}" (the nested substitution returns
an array in both cases), but not to "${${foo[2,4]}[2]}"
(the nested substitution returns a scalar because of
the quotes).
7. Modifiers
Any modifiers, as specified by a trailing `#', `%', `/'
(possibly doubled) or by a set of modifiers of the form
:... (see the section `Modifiers' in the section `His-
tory Expansion'), are applied to the words of the value
at this level.
8. Forced Joining
If the `(j)' flag is present, or no `(j)' flag is
present but the string is to be split as given by rules
8. or 9., and joining did not take place at step 4.,
any words in the value are joined together using the
given string or the first character of $IFS if none.
Note that the `(F)' flag implicitly supplies a string
for joining in this manner.
9. Forced Splitting
If one of the `(s)', `(f)' or `(z)' flags are present,
or the `=' specifier was present (e.g. ${=var}), the
word is split on occurrences of the specified string,
or (for = with neither of the two flags present) any of
the characters in $IFS.
10. Shell Word Splitting
If no `(s)', `(f)' or `=' was given, but the word is
not quoted and the option SH_WORD_SPLIT is set, the
word is split on occurrences of any of the characters
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in $IFS. Note this step, too, takes place at all lev-
els of a nested substitution.
11. Uniqueness
If the result is an array and the `(u)' flag was
present, duplicate elements are removed from the array.
12. Ordering
If the result is still an array and one of the `(o)' or
`(O)' flags was present, the array is reordered.
13. Re-Evaluation
Any `(e)' flag is applied to the value, forcing it to
be re-examined for new parameter substitutions, but
also for command and arithmetic substitutions.
14. Padding
Any padding of the value by the `(l.fill.)' or
`(r.fill.)' flags is applied.
15. Semantic Joining
In contexts where expansion semantics requires a single
word to result, all words are rejoined with the first
character of IFS between. So in `${(P)${(f)lines}}'
the value of ${lines} is split at newlines, but then
must be joined again before the P flag can be applied.
If a single word is not required, this rule is skipped.
Examples
The flag f is useful to split a double-quoted substitution
line by line. For example, ${(f)"$( contents of file divided so that each line is an element of
the resulting array. Compare this with the effect of
$( same inside double quotes, which makes the entire content of
the file a single string.
The following illustrates the rules for nested parameter
expansions. Suppose that $foo contains the array (bar baz):
"${(@)${foo}[1]}"
This produces the result b. First, the inner substitu-
tion "${foo}", which has no array (@) flag, produces a
single word result "bar baz". The outer substitution
"${(@)...[1]}" detects that this is a scalar, so that
(despite the `(@)' flag) the subscript picks the first
character.
"${${(@)foo}[1]}"
This produces the result `bar'. In this case, the
inner substitution "${(@)foo}" produces the array `(bar
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baz)'. The outer substitution "${...[1]}" detects that
this is an array and picks the first word. This is
similar to the simple case "${foo[1]}".
As an example of the rules for word splitting and joining,
suppose $foo contains the array `(ax1 bx1)'. Then
${(s/x/)foo}
produces the words `a', `1 b' and `1'.
${(j/x/s/x/)foo}
produces `a', `1', `b' and `1'.
${(s/x/)foo%%1*}
produces `a' and ` b' (note the extra space). As sub-
stitution occurs before either joining or splitting,
the operation first generates the modified array (ax
bx), which is joined to give "ax bx", and then split to
give `a', ` b' and `'. The final empty string will
then be elided, as it is not in double quotes.
COMMAND SUBSTITUTION
A command enclosed in parentheses preceded by a dollar sign,
like `$(...)', or quoted with grave accents, like ``...`',
is replaced with its standard output, with any trailing new-
lines deleted. If the substitution is not enclosed in dou-
ble quotes, the output is broken into words using the IFS
parameter. The substitution `$(cat foo)' may be replaced by
the equivalent but faster `$( option GLOB_SUBST is set, the output is eligible for
filename generation.
ARITHMETIC EXPANSION
A string of the form `$[exp]' or `$((exp))' is substituted
with the value of the arithmetic expression exp. exp is
subjected to parameter expansion, command substitution and
arithmetic expansion before it is evaluated. See the sec-
tion `Arithmetic Evaluation'.
BRACE EXPANSION
A string of the form `foo{xx,yy,zz}bar' is expanded to the
individual words `fooxxbar', `fooyybar' and `foozzbar'.
Left-to-right order is preserved. This construct may be
nested. Commas may be quoted in order to include them
literally in a word.
An expression of the form `{n1..n2}', where n1 and n2 are
integers, is expanded to every number between n1 and n2
inclusive. If either number begins with a zero, all the
resulting numbers will be padded with leading zeroes to that
minimum width. If the numbers are in decreasing order the
resulting sequence will also be in decreasing order.
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If a brace expression matches none of the above forms, it is
left unchanged, unless the option BRACE_CCL (an abbreviation
for `brace character class') is set. In that case, it is
expanded to a list of the individual characters between the
braces sorted into the order of the characters in the ASCII
character set (multibyte characters are not currently han-
dled). The syntax is similar to a [...] expression in
filename generation: `-' is treated specially to denote a
range of characters, but `^' or `!' as the first character
is treated normally. For example, `{abcdef0-9}' expands to
16 words 0 1 2 3 4 5 6 7 8 9 a b c d e f.
Note that brace expansion is not part of filename generation
(globbing); an expression such as */{foo,bar} is split into
two separate words */foo and */bar before filename genera-
tion takes place. In particular, note that this is liable
to produce a `no match' error if either of the two expres-
sions does not match; this is to be contrasted with
*/(foo|bar), which is treated as a single pattern but other-
wise has similar effects.
To combine brace expansion with array expansion, see the
${^spec} form described in the section Parameter Expansion
above.
FILENAME EXPANSION
Each word is checked to see if it begins with an unquoted
`~'. If it does, then the word up to a `/', or the end of
the word if there is no `/', is checked to see if it can be
substituted in one of the ways described here. If so, then
the `~' and the checked portion are replaced with the
appropriate substitute value.
A `~' by itself is replaced by the value of $HOME. A `~'
followed by a `+' or a `-' is replaced by the value of $PWD
or $OLDPWD, respectively.
A `~' followed by a number is replaced by the directory at
that position in the directory stack. `~0' is equivalent to
`~+', and `~1' is the top of the stack. `~+' followed by a
number is replaced by the directory at that position in the
directory stack. `~+0' is equivalent to `~+', and `~+1' is
the top of the stack. `~-' followed by a number is replaced
by the directory that many positions from the bottom of the
stack. `~-0' is the bottom of the stack. The PUSHD_MINUS
option exchanges the effects of `~+' and `~-' where they are
followed by a number.
Dynamic named directories
The feature described here is only available if the shell
function zsh_directory_name exists.
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A `~' followed by a string namstr in unquoted square brack-
ets is treated specially as a dynamic directory name. Note
that the first unquoted closing square bracket always ter-
minates namstr. The shell function is passed two arguments:
the string n (for name) and namstr. It should either set
the array reply to a single element which is the directory
corresponding to the name and return status zero (executing
an assignment as the last statement is usually sufficient),
or it should return status non-zero. In the former case the
element of reply is used as the directory; in the latter
case the substitution is deemed to have failed and NOMATCH
handling is applied if the option is set.
The function zsh_directory_name is also used to see if a
directory can be turned into a name, for example when print-
ing the directory stack or when expanding %~ in prompts. In
this case the function is passed two arguments: the string d
(for directory) and the candidate for dynamic naming. The
function should either return non-zero status, if the direc-
tory cannot be named by the function, or it should set the
array reply to consist of two elements: the first is the
dynamic name for the directory (as would appear within
`~[...]'), and the second is the prefix length of the direc-
tory to be replaced. For example, if the trial directory is
/home/myname/src/zsh and the dynamic name for
/home/myname/src (which has 16 characters) is s, then the
function sets
reply=(s 16)
The directory name so returned is compared with possible
static names for parts of the directory path, as described
below; it is used if the prefix length matched (16 in the
example) is longer than that matched by any static name.
As a working example, here is a function that expands any
dynamic names beginning with the string p: to directories
below /home/pws/perforce. In this simple case a static name
for the directory would be just as effective.
zsh_directory_name() {
emulate -L zsh
setopt extendedglob
local -a match mbegin mend
if [[ $1 = d ]]; then
if [[ $2 = (#b)(/home/pws/perforce/)([^/]##)* ]]; then
typeset -ga reply
reply=(p:$match[2] $(( ${#match[1]} + ${#match[2]} )) )
else
return 1
fi
else
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[[ $2 != (#b)p:(?*) ]] && return 1
typeset -ga reply
reply=(/home/pws/perforce/$match[1])
fi
return 0
}
Static named directories
A `~' followed by anything not already covered consisting of
any number of alphanumeric characters or underscore (`_'),
hyphen (`-'), or dot (`.') is looked up as a named direc-
tory, and replaced by the value of that named directory if
found. Named directories are typically home directories for
users on the system. They may also be defined if the text
after the `~' is the name of a string shell parameter whose
value begins with a `/'. Note that trailing slashes will be
removed from the path to the directory (though the original
parameter is not modified).
It is also possible to define directory names using the -d
option to the hash builtin.
In certain circumstances (in prompts, for instance), when
the shell prints a path, the path is checked to see if it
has a named directory as its prefix. If so, then the prefix
portion is replaced with a `~' followed by the name of the
directory. The shortest way of referring to the directory
is used, with ties broken in favour of using a named direc-
tory, except when the directory is / itself. The parameters
$PWD and $OLDPWD are never abbreviated in this fashion.
`=' expansion
If a word begins with an unquoted `=' and the EQUALS option
is set, the remainder of the word is taken as the name of a
command. If a command exists by that name, the word is
replaced by the full pathname of the command.
Notes
Filename expansion is performed on the right hand side of a
parameter assignment, including those appearing after com-
mands of the typeset family. In this case, the right hand
side will be treated as a colon-separated list in the manner
of the PATH parameter, so that a `~' or an `=' following a
`:' is eligible for expansion. All such behaviour can be
disabled by quoting the `~', the `=', or the whole expres-
sion (but not simply the colon); the EQUALS option is also
respected.
If the option MAGIC_EQUAL_SUBST is set, any unquoted shell
argument in the form `identifier=expression' becomes eligi-
ble for file expansion as described in the previous para-
graph. Quoting the first `=' also inhibits this.
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FILENAME GENERATION
If a word contains an unquoted instance of one of the char-
acters `*', `(', `|', `<', `[', or `?', it is regarded as a
pattern for filename generation, unless the GLOB option is
unset. If the EXTENDED_GLOB option is set, the `^' and `#'
characters also denote a pattern; otherwise they are not
treated specially by the shell.
The word is replaced with a list of sorted filenames that
match the pattern. If no matching pattern is found, the
shell gives an error message, unless the NULL_GLOB option is
set, in which case the word is deleted; or unless the
NOMATCH option is unset, in which case the word is left
unchanged.
In filename generation, the character `/' must be matched
explicitly; also, a `.' must be matched explicitly at the
beginning of a pattern or after a `/', unless the GLOB_DOTS
option is set. No filename generation pattern matches the
files `.' or `..'. In other instances of pattern matching,
the `/' and `.' are not treated specially.
Glob Operators
* Matches any string, including the null string.
? Matches any character.
[...]
Matches any of the enclosed characters. Ranges of
characters can be specified by separating two charac-
ters by a `-'. A `-' or `]' may be matched by includ-
ing it as the first character in the list. There are
also several named classes of characters, in the form
`[:name:]' with the following meanings. The first set
use the macros provided by the operating system to test
for the given character combinations, including any
modifications due to local language settings, see
ctype(3):
[:alnum:]
The character is alphanumeric
[:alpha:]
The character is alphabetic
[:ascii:]
The character is 7-bit, i.e. is a single-byte
character without the top bit set.
[:blank:]
The character is either space or tab
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[:cntrl:]
The character is a control character
[:digit:]
The character is a decimal digit
[:graph:]
The character is a printable character other than
whitespace
[:lower:]
The character is a lowercase letter
[:print:]
The character is printable
[:punct:]
The character is printable but neither
alphanumeric nor whitespace
[:space:]
The character is whitespace
[:upper:]
The character is an uppercase letter
[:xdigit:]
The character is a hexadecimal digit
Another set of named classes is handled internally by
the shell and is not sensitive to the locale:
[:IDENT:]
The character is allowed to form part of a shell
identifier, such as a parameter name
[:IFS:]
The character is used as an input field separator,
i.e. is contained in the IFS parameter
[:IFSSPACE:]
The character is an IFS white space character; see
the documentation for IFS in the zshparam(1)
manual page.
[:WORD:]
The character is treated as part of a word; this
test is sensitive to the value of the WORDCHARS
parameter
Note that the square brackets are additional to those
enclosing the whole set of characters, so to test for a
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single alphanumeric character you need `[[:alnum:]]'.
Named character sets can be used alongside other types,
e.g. `[[:alpha:]0-9]'.
[^...]
[!...]
Like [...], except that it matches any character which
is not in the given set.
<[x]-[y]>
Matches any number in the range x to y, inclusive.
Either of the numbers may be omitted to make the range
open-ended; hence `<->' matches any number. To match
individual digits, the [...] form is more efficient.
Be careful when using other wildcards adjacent to pat-
terns of this form; for example, <0-9>* will actually
match any number whatsoever at the start of the string,
since the `<0-9>' will match the first digit, and the
`*' will match any others. This is a trap for the
unwary, but is in fact an inevitable consequence of the
rule that the longest possible match always succeeds.
Expressions such as `<0-9>[^[:digit:]]*' can be used
instead.
(...)
Matches the enclosed pattern. This is used for group-
ing. If the KSH_GLOB option is set, then a `@', `*',
`+', `?' or `!' immediately preceding the `(' is
treated specially, as detailed below. The option
SH_GLOB prevents bare parentheses from being used in
this way, though the KSH_GLOB option is still avail-
able.
Note that grouping cannot extend over multiple direc-
tories: it is an error to have a `/' within a group
(this only applies for patterns used in filename gen-
eration). There is one exception: a group of the form
(pat/)# appearing as a complete path segment can match
a sequence of directories. For example, foo/(a*/)#bar
matches foo/bar, foo/any/bar, foo/any/anyother/bar, and
so on.
x|y Matches either x or y. This operator has lower pre-
cedence than any other. The `|' character must be
within parentheses, to avoid interpretation as a pipe-
line.
^x (Requires EXTENDED_GLOB to be set.) Matches anything
except the pattern x. This has a higher precedence
than `/', so `^foo/bar' will search directories in `.'
except `./foo' for a file named `bar'.
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x~y (Requires EXTENDED_GLOB to be set.) Match anything
that matches the pattern x but does not match y. This
has lower precedence than any operator except `|', so
`*/*~foo/bar' will search for all files in all direc-
tories in `.' and then exclude `foo/bar' if there was
such a match. Multiple patterns can be excluded by
`foo~bar~baz'. In the exclusion pattern (y), `/' and
`.' are not treated specially the way they usually are
in globbing.
x# (Requires EXTENDED_GLOB to be set.) Matches zero or
more occurrences of the pattern x. This operator has
high precedence; `12#' is equivalent to `1(2#)', rather
than `(12)#'. It is an error for an unquoted `#' to
follow something which cannot be repeated; this
includes an empty string, a pattern already followed by
`##', or parentheses when part of a KSH_GLOB pattern
(for example, `!(foo)#' is invalid and must be replaced
by `*(!(foo))').
x## (Requires EXTENDED_GLOB to be set.) Matches one or
more occurrences of the pattern x. This operator has
high precedence; `12##' is equivalent to `1(2##)',
rather than `(12)##'. No more than two active `#'
characters may appear together. (Note the potential
clash with glob qualifiers in the form `1(2##)' which
should therefore be avoided.)
ksh-like Glob Operators
If the KSH_GLOB option is set, the effects of parentheses
can be modified by a preceding `@', `*', `+', `?' or `!'.
This character need not be unquoted to have special effects,
but the `(' must be.
@(...)
Match the pattern in the parentheses. (Like `(...)'.)
*(...)
Match any number of occurrences. (Like `(...)#'.)
+(...)
Match at least one occurrence. (Like `(...)##'.)
?(...)
Match zero or one occurrence. (Like `(|...)'.)
!(...)
Match anything but the expression in parentheses.
(Like `(^(...))'.)
Precedence
The precedence of the operators given above is (highest)
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`^', `/', `~', `|' (lowest); the remaining operators are
simply treated from left to right as part of a string, with
`#' and `##' applying to the shortest possible preceding
unit (i.e. a character, `?', `[...]', `<...>', or a
parenthesised expression). As mentioned above, a `/' used
as a directory separator may not appear inside parentheses,
while a `|' must do so; in patterns used in other contexts
than filename generation (for example, in case statements
and tests within `[[...]]'), a `/' is not special; and `/'
is also not special after a `~' appearing outside
parentheses in a filename pattern.
Globbing Flags
There are various flags which affect any text to their right
up to the end of the enclosing group or to the end of the
pattern; they require the EXTENDED_GLOB option. All take the
form (#X) where X may have one of the following forms:
i Case insensitive: upper or lower case characters in
the pattern match upper or lower case characters.
l Lower case characters in the pattern match upper or
lower case characters; upper case characters in the
pattern still only match upper case characters.
I Case sensitive: locally negates the effect of i or l
from that point on.
b Activate backreferences for parenthesised groups in the
pattern; this does not work in filename generation.
When a pattern with a set of active parentheses is
matched, the strings matched by the groups are stored
in the array $match, the indices of the beginning of
the matched parentheses in the array $mbegin, and the
indices of the end in the array $mend, with the first
element of each array corresponding to the first
parenthesised group, and so on. These arrays are not
otherwise special to the shell. The indices use the
same convention as does parameter substitution, so that
elements of $mend and $mbegin may be used in sub-
scripts; the KSH_ARRAYS option is respected. Sets of
globbing flags are not considered parenthesised groups;
only the first nine active parentheses can be refer-
enced.
For example,
foo="a string with a message"
if [[ $foo = (a|an)' '(#b)(*)' '* ]]; then
print ${foo[$mbegin[1],$mend[1]]}
fi
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prints `string with a'. Note that the first
parenthesis is before the (#b) and does not create a
backreference.
Backreferences work with all forms of pattern matching
other than filename generation, but note that when per-
forming matches on an entire array, such as
${array#pattern}, or a global substitution, such as
${param//pat/repl}, only the data for the last match
remains available. In the case of global replacements
this may still be useful. See the example for the m
flag below.
The numbering of backreferences strictly follows the
order of the opening parentheses from left to right in
the pattern string, although sets of parentheses may be
nested. There are special rules for parentheses fol-
lowed by `#' or `##'. Only the last match of the
parenthesis is remembered: for example, in `[[ abab =
(#b)([ab])# ]]', only the final `b' is stored in
match[1]. Thus extra parentheses may be necessary to
match the complete segment: for example, use
`X((ab|cd)#)Y' to match a whole string of either `ab'
or `cd' between `X' and `Y', using the value of
$match[1] rather than $match[2].
If the match fails none of the parameters is altered,
so in some cases it may be necessary to initialise them
beforehand. If some of the backreferences fail to
match -- which happens if they are in an alternate
branch which fails to match, or if they are followed by
# and matched zero times -- then the matched string is
set to the empty string, and the start and end indices
are set to -1.
Pattern matching with backreferences is slightly slower
than without.
B Deactivate backreferences, negating the effect of the b
flag from that point on.
cN,M The flag (#cN,M) can be used anywhere that the # or ##
operators can be used; it cannot be combined with other
globbing flags and a bad pattern error occurs if it is
misplaced. It is equivalent to the form {N,M} in regu-
lar expressions. The previous character or group is
required to match between N and M times, inclusive.
The form (#cN) requires exactly N matches; (#c,M) is
equivalent to specifying N as 0; (#cN,) specifies that
there is no maximum limit on the number of matches.
m Set references to the match data for the entire string
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matched; this is similar to backreferencing and does
not work in filename generation. The flag must be in
effect at the end of the pattern, i.e. not local to a
group. The parameters $MATCH, $MBEGIN and $MEND will
be set to the string matched and to the indices of the
beginning and end of the string, respectively. This is
most useful in parameter substitutions, as otherwise
the string matched is obvious.
For example,
arr=(veldt jynx grimps waqf zho buck)
print ${arr//(#m)[aeiou]/${(U)MATCH}}
forces all the matches (i.e. all vowels) into upper-
case, printing `vEldt jynx grImps wAqf zhO bUck'.
Unlike backreferences, there is no speed penalty for
using match references, other than the extra substitu-
tions required for the replacement strings in cases
such as the example shown.
M Deactivate the m flag, hence no references to match
data will be created.
anum Approximate matching: num errors are allowed in the
string matched by the pattern. The rules for this are
described in the next subsection.
s, e Unlike the other flags, these have only a local effect,
and each must appear on its own: `(#s)' and `(#e)' are
the only valid forms. The `(#s)' flag succeeds only at
the start of the test string, and the `(#e)' flag
succeeds only at the end of the test string; they
correspond to `^' and `$' in standard regular expres-
sions. They are useful for matching path segments in
patterns other than those in filename generation (where
path segments are in any case treated separately). For
example, `*((#s)|/)test((#e)|/)*' matches a path seg-
ment `test' in any of the following strings: test,
test/at/start, at/end/test, in/test/middle.
Another use is in parameter substitution; for example
`${array/(#s)A*Z(#e)}' will remove only elements of an
array which match the complete pattern `A*Z'. There
are other ways of performing many operations of this
type, however the combination of the substitution
operations `/' and `//' with the `(#s)' and `(#e)'
flags provides a single simple and memorable method.
Note that assertions of the form `(^(#s))' also work,
i.e. match anywhere except at the start of the string,
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although this actually means `anything except a
zero-length portion at the start of the string'; you
need to use `(""~(#s))' to match a zero-length portion
of the string not at the start.
q A `q' and everything up to the closing parenthesis of
the globbing flags are ignored by the pattern matching
code. This is intended to support the use of glob
qualifiers, see below. The result is that the pattern
`(#b)(*).c(#q.)' can be used both for globbing and for
matching against a string. In the former case, the
`(#q.)' will be treated as a glob qualifier and the
`(#b)' will not be useful, while in the latter case the
`(#b)' is useful for backreferences and the `(#q.)'
will be ignored. Note that colon modifiers in the glob
qualifiers are also not applied in ordinary pattern
matching.
u Respect the current locale in determining the presence
of multibyte characters in a pattern, provided the
shell was compiled with MULTIBYTE_SUPPORT. This over-
rides the MULTIBYTE option; the default behaviour is
taken from the option. Compare U. (Mnemonic: typi-
cally multibyte characters are from Unicode in the
UTF-8 encoding, although any extension of ASCII sup-
ported by the system library may be used.)
U All characters are considered to be a single byte long.
The opposite of u. This overrides the MULTIBYTE
option.
For example, the test string fooxx can be matched by the
pattern (#i)FOOXX, but not by (#l)FOOXX, (#i)FOO(#I)XX or
((#i)FOOX)X. The string (#ia2)readme specifies
case-insensitive matching of readme with up to two errors.
When using the ksh syntax for grouping both KSH_GLOB and
EXTENDED_GLOB must be set and the left parenthesis should be
preceded by @. Note also that the flags do not affect
letters inside [...] groups, in other words (#i)[a-z] still
matches only lowercase letters. Finally, note that when
examining whole paths case-insensitively every directory
must be searched for all files which match, so that a pat-
tern of the form (#i)/foo/bar/... is potentially slow.
Approximate Matching
When matching approximately, the shell keeps a count of the
errors found, which cannot exceed the number specified in
the (#anum) flags. Four types of error are recognised:
1. Different characters, as in fooxbar and fooybar.
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2. Transposition of characters, as in banana and abnana.
3. A character missing in the target string, as with the
pattern road and target string rod.
4. An extra character appearing in the target string, as
with stove and strove.
Thus, the pattern (#a3)abcd matches dcba, with the errors
occurring by using the first rule twice and the second once,
grouping the string as [d][cb][a] and [a][bc][d].
Non-literal parts of the pattern must match exactly, includ-
ing characters in character ranges: hence (#a1)??? matches
strings of length four, by applying rule 4 to an empty part
of the pattern, but not strings of length two, since all the
? must match. Other characters which must match exactly are
initial dots in filenames (unless the GLOB_DOTS option is
set), and all slashes in filenames, so that a/bc is two
errors from ab/c (the slash cannot be transposed with
another character). Similarly, errors are counted
separately for non-contiguous strings in the pattern, so
that (ab|cd)ef is two errors from aebf.
When using exclusion via the ~ operator, approximate match-
ing is treated entirely separately for the excluded part and
must be activated separately. Thus, (#a1)README~READ_ME
matches READ.ME but not READ_ME, as the trailing READ_ME is
matched without approximation. However,
(#a1)README~(#a1)READ_ME does not match any pattern of the
form READ?ME as all such forms are now excluded.
Apart from exclusions, there is only one overall error
count; however, the maximum errors allowed may be altered
locally, and this can be delimited by grouping. For exam-
ple, (#a1)cat((#a0)dog)fox allows one error in total, which
may not occur in the dog section, and the pattern
(#a1)cat(#a0)dog(#a1)fox is equivalent. Note that the point
at which an error is first found is the crucial one for
establishing whether to use approximation; for example,
(#a1)abc(#a0)xyz will not match abcdxyz, because the error
occurs at the `x', where approximation is turned off.
Entire path segments may be matched approximately, so that
`(#a1)/foo/d/is/available/at/the/bar' allows one error in
any path segment. This is much less efficient than without
the (#a1), however, since every directory in the path must
be scanned for a possible approximate match. It is best to
place the (#a1) after any path segments which are known to
be correct.
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Recursive Globbing
A pathname component of the form `(foo/)#' matches a path
consisting of zero or more directories matching the pattern
foo.
As a shorthand, `**/' is equivalent to `(*/)#'; note that
this therefore matches files in the current directory as
well as subdirectories. Thus:
ls (*/)#bar
or
ls **/bar
does a recursive directory search for files named `bar'
(potentially including the file `bar' in the current direc-
tory). This form does not follow symbolic links; the alter-
native form `***/' does, but is otherwise identical. Nei-
ther of these can be combined with other forms of globbing
within the same path segment; in that case, the `*' opera-
tors revert to their usual effect.
Glob Qualifiers
Patterns used for filename generation may end in a list of
qualifiers enclosed in parentheses. The qualifiers specify
which filenames that otherwise match the given pattern will
be inserted in the argument list.
If the option BARE_GLOB_QUAL is set, then a trailing set of
parentheses containing no `|' or `(' characters (or `~' if
it is special) is taken as a set of glob qualifiers. A glob
subexpression that would normally be taken as glob qualif-
iers, for example `(^x)', can be forced to be treated as
part of the glob pattern by doubling the parentheses, in
this case producing `((^x))'.
If the option EXTENDED_GLOB is set, a different syntax for
glob qualifiers is available, namely `(#qx)' where x is any
of the same glob qualifiers used in the other format. The
qualifiers must still appear at the end of the pattern.
However, with this syntax multiple glob qualifiers may be
chained together. They are treated as a logical AND of the
individual sets of flags. Also, as the syntax is unambigu-
ous, the expression will be treated as glob qualifiers just
as long any parentheses contained within it are balanced;
appearance of `|', `(' or `~' does not negate the effect.
Note that qualifiers will be recognised in this form even if
a bare glob qualifier exists at the end of the pattern, for
example `*(#q*)(.)' will recognise executable regular files
if both options are set; however, mixed syntax should prob-
ably be avoided for the sake of clarity.
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A qualifier may be any one of the following:
/ directories
F `full' (i.e. non-empty) directories. Note that the
opposite sense (^F) expands to empty directories and
all non-directories. Use (/^F) for empty directories
. plain files
@ symbolic links
= sockets
p named pipes (FIFOs)
* executable plain files (0100)
% device files (character or block special)
%b block special files
%c character special files
r owner-readable files (0400)
w owner-writable files (0200)
x owner-executable files (0100)
A group-readable files (0040)
I group-writable files (0020)
E group-executable files (0010)
R world-readable files (0004)
W world-writable files (0002)
X world-executable files (0001)
s setuid files (04000)
S setgid files (02000)
t files with the sticky bit (01000)
fspec
files with access rights matching spec. This spec may
be a octal number optionally preceded by a `=', a `+',
or a `-'. If none of these characters is given, the
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behavior is the same as for `='. The octal number
describes the mode bits to be expected, if combined
with a `=', the value given must match the file-modes
exactly, with a `+', at least the bits in the given
number must be set in the file-modes, and with a `-',
the bits in the number must not be set. Giving a `?'
instead of a octal digit anywhere in the number ensures
that the corresponding bits in the file-modes are not
checked, this is only useful in combination with `='.
If the qualifier `f' is followed by any other character
anything up to the next matching character (`[', `{',
and `<' match `]', `}', and `>' respectively, any other
character matches itself) is taken as a list of
comma-separated sub-specs. Each sub-spec may be either
an octal number as described above or a list of any of
the characters `u', `g', `o', and `a', followed by a
`=', a `+', or a `-', followed by a list of any of the
characters `r', `w', `x', `s', and `t', or an octal
digit. The first list of characters specify which
access rights are to be checked. If a `u' is given,
those for the owner of the file are used, if a `g' is
given, those of the group are checked, a `o' means to
test those of other users, and the `a' says to test all
three groups. The `=', `+', and `-' again says how the
modes are to be checked and have the same meaning as
described for the first form above. The second list of
characters finally says which access rights are to be
expected: `r' for read access, `w' for write access,
`x' for the right to execute the file (or to search a
directory), `s' for the setuid and setgid bits, and `t'
for the sticky bit.
Thus, `*(f70?)' gives the files for which the owner has
read, write, and execute permission, and for which
other group members have no rights, independent of the
permissions for other users. The pattern `*(f-100)'
gives all files for which the owner does not have exe-
cute permission, and `*(f:gu+w,o-rx:)' gives the files
for which the owner and the other members of the group
have at least write permission, and for which other
users don't have read or execute permission.
estring
+cmd The string will be executed as shell code. The
filename will be included in the list if and only if
the code returns a zero status (usually the status of
the last command). The first character after the `e'
will be used as a separator and anything up to the next
matching separator will be taken as the string; `[',
`{', and `<' match `]', `}', and `>', respectively,
while any other character matches itself. Note that
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expansions must be quoted in the string to prevent them
from being expanded before globbing is done.
During the execution of string the filename currently
being tested is available in the parameter REPLY; the
parameter may be altered to a string to be inserted
into the list instead of the original filename. In
addition, the parameter reply may be set to an array or
a string, which overrides the value of REPLY. If set
to an array, the latter is inserted into the command
line word by word.
For example, suppose a directory contains a single file
`lonely'. Then the expression
`*(e:'reply=(${REPLY}{1,2})':)' will cause the words
`lonely1 lonely2' to be inserted into the command line.
Note the quotation marks.
The form +cmd has the same effect, but no delimiters
appear around cmd. Instead, cmd is taken as the long-
est sequence of characters following the + that are
alphanumeric or underscore. Typically cmd will be the
name of a shell function that contains the appropriate
test. For example,
nt() { [[ $REPLY -nt $NTREF ]] }
NTREF=reffile
ls -l *(+nt)
lists all files in the directory that have been modi-
fied more recently than reffile.
ddev files on the device dev
l[-|+]ct
files having a link count less than ct (-), greater
than ct (+), or equal to ct
U files owned by the effective user ID
G files owned by the effective group ID
uid files owned by user ID id if that is a number. Other-
wise, id specifies a user name: the character after the
`u' will be taken as a separator and the string between
it and the next matching separator will be taken as a
user name. The starting separators `[', `{', and `<'
match the final separators `]', `}', and `>', respec-
tively; any other character matches itself. The
selected files are those owned by this user. For exam-
ple, `u:foo:' or `u[foo]' selects files owned by user
`foo'.
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gid like uid but with group IDs or names
a[Mwhms][-|+]n
files accessed exactly n days ago. Files accessed
within the last n days are selected using a negative
value for n (-n). Files accessed more than n days ago
are selected by a positive n value (+n). Optional unit
specifiers `M', `w', `h', `m' or `s' (e.g. `ah5') cause
the check to be performed with months (of 30 days),
weeks, hours, minutes or seconds instead of days,
respectively.
Any fractional part of the difference between the
access time and the current part in the appropriate
units is ignored in the comparison. For instance,
`echo *(ah-5)' would echo files accessed within the
last five hours, while `echo *(ah+5)' would echo files
accessed at least six hours ago, as times strictly
between five and six hours are treated as five hours.
m[Mwhms][-|+]n
like the file access qualifier, except that it uses the
file modification time.
c[Mwhms][-|+]n
like the file access qualifier, except that it uses the
file inode change time.
L[+|-]n
files less than n bytes (-), more than n bytes (+), or
exactly n bytes in length. If this flag is directly
followed by a `k' (`K'), `m' (`M'), or `p' (`P') (e.g.
`Lk-50') the check is performed with kilobytes, mega-
bytes, or blocks (of 512 bytes) instead.
^ negates all qualifiers following it
- toggles between making the qualifiers work on symbolic
links (the default) and the files they point to
M sets the MARK_DIRS option for the current pattern
T appends a trailing qualifier mark to the filenames,
analogous to the LIST_TYPES option, for the current
pattern (overrides M)
N sets the NULL_GLOB option for the current pattern
D sets the GLOB_DOTS option for the current pattern
n sets the NUMERIC_GLOB_SORT option for the current pat-
tern
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oc specifies how the names of the files should be sorted.
If c is n they are sorted by name (the default); if it
is L they are sorted depending on the size (length) of
the files; if l they are sorted by the number of links;
if a, m, or c they are sorted by the time of the last
access, modification, or inode change respectively; if
d, files in subdirectories appear before those in the
current directory at each level of the search -- this
is best combined with other criteria, for example
`odon' to sort on names for files within the same
directory; if N, no sorting is performed. Note that a,
m, and c compare the age against the current time,
hence the first name in the list is the youngest file.
Also note that the modifiers ^ and - are used, so
`*(^-oL)' gives a list of all files sorted by file size
in descending order, following any symbolic links.
Unless oN is used, multiple order specifiers may occur
to resolve ties.
oe and o+ are special cases; they are each followed by
shell code, delimited as for the e glob qualifier and
the + glob qualifier respectively (see above). The
code is executed for each matched file with the parame-
ter REPLY set to the name of the file on entry. The
code should modify the parameter REPLY in some fashion.
On return, the value of the parameter is used instead
of the file name as the string on which to sort.
Unlike other sort operators, oe and o+ may be repeated,
but note that the maximum number of sort operators of
any kind that may appear in any glob expression is 12.
Oc like `o', but sorts in descending order; i.e. `*(^oc)'
is the same as `*(Oc)' and `*(^Oc)' is the same as
`*(oc)'; `Od' puts files in the current directory
before those in subdirectories at each level of the
search.
[beg[,end]]
specifies which of the matched filenames should be
included in the returned list. The syntax is the same
as for array subscripts. beg and the optional end may
be mathematical expressions. As in parameter subscript-
ing they may be negative to make them count from the
last match backward. E.g.: `*(-OL[1,3])' gives a list
of the names of the three largest files.
More than one of these lists can be combined, separated by
commas. The whole list matches if at least one of the sub-
lists matches (they are `or'ed, the qualifiers in the sub-
lists are `and'ed). Some qualifiers, however, affect all
matches generated, independent of the sublist in which they
are given. These are the qualifiers `M', `T', `N', `D',
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User Commands ZSHEXPN(1)
`n', `o', `O' and the subscripts given in brackets
(`[...]').
If a `:' appears in a qualifier list, the remainder of the
expression in parenthesis is interpreted as a modifier (see
the section `Modifiers' in the section `History Expansion').
Each modifier must be introduced by a separate `:'. Note
also that the result after modification does not have to be
an existing file. The name of any existing file can be fol-
lowed by a modifier of the form `(:..)' even if no actual
filename generation is performed, although note that the
presence of the parentheses causes the entire expression to
be subjected to any global pattern matching options such as
NULL_GLOB. Thus:
ls *(-/)
lists all directories and symbolic links that point to
directories, and
ls *(%W)
lists all world-writable device files in the current direc-
tory, and
ls *(W,X)
lists all files in the current directory that are
world-writable or world-executable, and
echo /tmp/foo*(u0^@:t)
outputs the basename of all root-owned files beginning with
the string `foo' in /tmp, ignoring symlinks, and
ls *.*~(lex|parse).[ch](^D^l1)
lists all files having a link count of one whose names con-
tain a dot (but not those starting with a dot, since
GLOB_DOTS is explicitly switched off) except for lex.c,
lex.h, parse.c and parse.h.
print b*.pro(#q:s/pro/shmo/)(#q.:s/builtin/shmiltin/)
demonstrates how colon modifiers and other qualifiers may be
chained together. The ordinary qualifier `.' is applied
first, then the colon modifiers in order from left to right.
So if EXTENDED_GLOB is set and the base pattern matches the
regular file builtin.pro, the shell will print
`shmiltin.shmo'.
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User Commands ZSHEXPN(1)
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
_______________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE|
|____________________|__________________|_
| Availability | shell/zsh |
|____________________|__________________|_
| Interface Stability| External |
|____________________|_________________|
NOTES
Source for zsh is available on http://opensolaris.org.
zsh 4.3.10 Last change: June 1, 2009 43