Windows PowerShell command on Get-command nawk

Manual Pages for UNIX Operating System command usage for man nawk

User Commands nawk(1)

NAME

nawk - pattern scanning and processing language

SYNOPSIS

/usr/bin/nawk [-F ERE] [-v assignment] 'program' | -f progfile...

[argument]...

/usr/xpg4/bin/awk [-F ERE] [-v assignment]... 'program' | -f progfile...

[argument]...

DESCRIPTION

The /usr/bin/nawk and /usr/xpg4/bin/awk utilities execute

programs written in the nawk programming language, which is

specialized for textual data manipulation. A nawk program is

a sequence of patterns and corresponding actions. The string specifying program must be enclosed in single quotes (') to protect it from interpretation by the shell. The sequence of

pattern - action statements can be specified in the command

line as program or in one, or more, file(s) specified by the

-fprogfile option. When input is read that matches a pat-

tern, the action associated with the pattern is performed. Input is interpreted as a sequence of records. By default, a record is a line, but this can be changed by using the RS

built-in variable. Each record of input is matched to each

pattern in the program. For each pattern matched, the asso-

ciated action is executed.

The nawk utility interprets each input record as a sequence

of fields where, by default, a field is a string of non-

blank characters. This default white-space field delimiter

(blanks and/or tabs) can be changed by using the FS built-in

variable or the -FERE option. The nawk utility denotes the

first field in a record $1, the second $2, and so forth. The

symbol $0 refers to the entire record; setting any other

field causes the reevaluation of $0. Assigning to $0 resets

the values of all fields and the NF built-in variable.

OPTIONS The following options are supported:

-F ERE Define the input field separator to be the

extended regular expression ERE, before any input is read (can be a character).

-f progfile Specifies the pathname of the file progfile

containing a nawk program. If multiple

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User Commands nawk(1)

instances of this option are specified, the concatenation of the files specified as

progfile in the order specified is the nawk

program. The nawk program can alternatively

be specified in the command line as a sin-

gle argument.

-v assignment The assignment argument must be in the same

form as an assignment operand. The assign-

ment is of the form var=value, where var is the name of one of the variables described below. The specified assignment occurs

before executing the nawk program, includ-

ing the actions associated with BEGIN pat-

terns (if any). Multiple occurrences of this option can be specified. OPERANDS The following operands are supported:

program If no -f option is specified, the first operand

to nawk is the text of the nawk program. The

application supplies the program operand as a

single argument to nawk. If the text does not

end in a newline character, nawk interprets the

text as if it did. argument Either of the following two types of argument can be intermixed: file A pathname of a file that contains the input to be read, which is

matched against the set of pat-

terns in the program. If no file operands are specified, or if a

file operand is -, the standard

input is used. assignment An operand that begins with an underscore or alphabetic character from the portable character set,

followed by a sequence of under-

scores, digits and alphabetics from the portable character set,

followed by the = character speci-

fies a variable assignment rather than a pathname. The characters before the = represent the name of

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User Commands nawk(1)

a nawk variable. If that name is a

nawk reserved word, the behavior

is undefined. The characters fol-

lowing the equal sign is inter-

preted as if they appeared in the

nawk program preceded and followed

by a double-quote (") character,

as a STRING token , except that if the last character is an unescaped backslash, it is interpreted as a literal backslash rather than as the first character of the sequence \.. The variable is assigned the value of that STRING token. If the value is considered a numericstring, the variable is assigned its numeric value. Each

such variable assignment is per-

formed just before the processing of the following file, if any. Thus, an assignment before the first file argument is executed after the BEGIN actions (if any), while an assignment after the last file argument is executed before the END actions (if any). If there are no file arguments, assignments are executed before processing the standard input.

INPUT FILES

Input files to the nawk program from any of the following

sources: o any file operands or their equivalents, achieved by

modifying the nawk variables ARGV and ARGC

o standard input in the absence of any file operands o arguments to the getline function must be text files. Whether the variable RS is set to a value other than a newline character or not, for these files, implementations support records terminated with the

specified separator up to {LINE_MAX} bytes and can support

longer records.

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If -f progfile is specified, the files named by each of the

progfile option-arguments must be text files containing an

nawk program.

The standard input are used only if no file operands are

specified, or if a file operand is -.

EXTENDED DESCRIPTION

A nawk program is composed of pairs of the form:

pattern { action } Either the pattern or the action (including the enclosing

brace characters) can be omitted. Pattern-action statements

are separated by a semicolon or by a newline. A missing pattern matches any record of input, and a missing action is equivalent to an action that writes the matched record of input to standard output.

Execution of the nawk program starts by first executing the

actions associated with all BEGIN patterns in the order they occur in the program. Then each file operand (or standard input if no files were specified) is processed by reading

data from the file until a record separator is seen (a new-

line character by default), splitting the current record into fields using the current value of FS, evaluating each

pattern in the program in the order of occurrence, and exe-

cuting the action associated with each pattern that matches the current record. The action for a matching pattern is executed before evaluating subsequent patterns. Last, the actions associated with all END patterns is executed in the order they occur in the program.

Expressions in nawk

Expressions describe computations used in patterns and actions. In the following table, valid expression operations are given in groups from highest precedence first to lowest

precedence last, with equal-precedence operators grouped

between horizontal lines. In expression evaluation, where

the grammar is formally ambiguous, higher precedence opera-

tors are evaluated before lower precedence operators. In this table expr, expr1, expr2, and expr3 represent any expression, while lvalue represents any entity that can be assigned to (that is, on the left side of an assignment operator).

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Syntax Name Type of Result Associativity

_______________________________________________________________________________

( expr ) Grouping type of expr n/a

_______________________________________________________________________________

$expr Field reference string n/a

_______________________________________________________________________________

++ lvalue Pre-increment numeric n/a

--lvalue Pre-decrement numeric n/a

lvalue ++ Post-increment numeric n/a

lvalue -- Post-decrement numeric n/a

_______________________________________________________________________________

expr ^ expr Exponentiation numeric right

_______________________________________________________________________________

! expr Logical not numeric n/a + expr Unary plus numeric n/a

- expr Unary minus numeric n/a

_______________________________________________________________________________

expr * expr Multiplication numeric left expr / expr Division numeric left

expr % expr Modulus numeric left

_______________________________________________________________________________

expr + expr Addition numeric left

expr - expr Subtraction numeric left

_______________________________________________________________________________

expr expr String concatenation string left

_______________________________________________________________________________

expr < expr Less than numeric none expr <= expr Less than or equal to numeric none expr != expr Not equal to numeric none expr == expr Equal to numeric none expr > expr Greater than numeric none expr >= expr Greater than or equal to numeric none

_______________________________________________________________________________

expr ~ expr ERE match numeric none

expr !~ expr ERE non-match numeric none

_______________________________________________________________________________

expr in array Array membership numeric left

( index ) in Multi-dimension array numeric left

array membership

_______________________________________________________________________________

expr && expr Logical AND numeric left

_______________________________________________________________________________

expr || expr Logical OR numeric left

_______________________________________________________________________________

expr1 ? expr2 Conditional expression type of selected right : expr3 expr2 or expr3

_______________________________________________________________________________

lvalue ^= expr Exponentiation numeric right assignment

lvalue %= expr Modulus assignment numeric right

lvalue *= expr Multiplication numeric right assignment

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lvalue /= expr Division assignment numeric right lvalue += expr Addition assignment numeric right

lvalue -= expr Subtraction assignment numeric right

lvalue = expr Assignment type of expr right Each expression has either a string value, a numeric value or both. Except as stated for specific contexts, the value of an expression is implicitly converted to the type needed

for the context in which it is used. A string value is con-

verted to a numeric value by the equivalent of the following calls:

setlocale(LC_NUMERIC, "");

numeric_value = atof(string_value);

A numeric value that is exactly equal to the value of an integer is converted to a string by the equivalent of a call

to the sprintf function with the string %d as the fmt argu-

ment and the numeric value being converted as the first and only expr argument. Any other numeric value is converted to a string by the equivalent of a call to the sprintf function with the value of the variable CONVFMT as the fmt argument and the numeric value being converted as the first and only expr argument. A string value is considered to be a numeric string in the following case: 1. Any leading and trailing blank characters is ignored.

2. If the first unignored character is a + or -, it is

ignored.

3. If the remaining unignored characters would be lex-

ically recognized as a NUMBER token, the string is considered a numeric string.

If a - character is ignored in the above steps, the numeric

value of the numeric string is the negation of the numeric value of the recognized NUMBER token. Otherwise the numeric value of the numeric string is the numeric value of the recognized NUMBER token. Whether or not a string is a numeric string is relevant only in contexts where that term is used in this section.

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When an expression is used in a Boolean context, if it has a numeric value, a value of zero is treated as false and any other value is treated as true. Otherwise, a string value of the null string is treated as false and any other value is treated as true. A Boolean context is one of the following:

o the first subexpression of a conditional expres-

sion. o an expression operated on by logical NOT, logical AND, or logical OR. o the second expression of a for statement. o the expression of an if statement. o the expression of the while clause in either a while or do ... while statement.

o an expression used as a pattern (as in Overall Pro-

gram Structure).

The nawk language supplies arrays that are used for storing

numbers or strings. Arrays need not be declared. They are initially empty, and their sizes changes dynamically. The subscripts, or element identifiers, are strings, providing a type of associative array capability. An array name followed by a subscript within square brackets can be used as an lvalue and as an expression, as described in the grammar. Unsubscripted array names are used in only the following contexts: o a parameter in a function definition or function call.

o the NAME token following any use of the keyword in.

A valid array index consists of one or more comma-separated

expressions, similar to the way in which multi-dimensional

arrays are indexed in some programming languages. Because

nawk arrays are really one-dimensional, such a comma-

separated list is converted to a single string by con-

catenating the string values of the separate expressions, each separated from the other by the value of the SUBSEP variable. Thus, the following two index operations are equivalent: var[expr1, expr2, ... exprn]

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var[expr1 SUBSEP expr2 SUBSEP ... SUBSEP exprn]

A multi-dimensioned index used with the in operator must be

put in parentheses. The in operator, which tests for the existence of a particular array element, does not create the element if it does not exist. Any other reference to a

non-existent array element automatically creates it.

Variables and Special Variables

Variables can be used in an nawk program by referencing

them. With the exception of function parameters, they are not explicitly declared. Uninitialized scalar variables and array elements have both a numeric value of zero and a string value of the empty string.

Field variables are designated by a $ followed by a number

or numerical expression. The effect of the field number

expression evaluating to anything other than a non-negative

integer is unspecified. Uninitialized variables or string

values need not be converted to numeric values in this con-

text. New field variables are created by assigning a value

to them. References to non-existent fields (that is, fields

after $NF) produce the null string. However, assigning to a

non-existent field (for example, $(NF+2) = 5) increases the

value of NF, create any intervening fields with the null

string as their values and cause the value of $0 to be

recomputed, with the fields being separated by the value of OFS. Each field variable has a string value when created. If

the string, with any occurrence of the decimal-point charac-

ter from the current locale changed to a period character,

is considered a numeric string (see Expressions in nawk

above), the field variable also has the numeric value of the numeric string.

/usr/bin/nawk, /usr/xpg4/bin/awk

nawk sets the following special variables that are supported

by both /usr/bin/nawk and /usr/xpg4/bin/awk:

ARGC The number of elements in the ARGV array. ARGV An array of command line arguments, excluding options and the program argument, numbered from

zero to ARGC-1.

The arguments in ARGV can be modified or added to; ARGC can be altered. As each input file

ends, nawk treats the next non-null element of

ARGV, up to the current value of ARGC-1,

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inclusive, as the name of the next input file. Setting an element of ARGV to null means that it

is not treated as an input file. The name -

indicates the standard input. If an argument matches the format of an assignment operand, this argument is treated as an assignment rather than a file argument. ENVIRON The variable ENVIRON is an array representing the value of the environment. The indices of the array are strings consisting of the names of the environment variables, and the value of each array element is a string consisting of the value of that variable. If the value of an environment variable is considered a numeric string, the array element also has its numeric value.

In all cases where nawk behavior is affected by

environment variables (including the environment

of any commands that nawk executes via the sys-

tem function or via pipeline redirections with the print statement, the printf statement, or the getline function), the environment used is

the environment at the time nawk began execut-

ing.

FILENAME A pathname of the current input file. Inside a

BEGIN action the value is undefined. Inside an END action the value is the name of the last input file processed. FNR The ordinal number of the current record in the current file. Inside a BEGIN action the value is zero. Inside an END action the value is the number of the last record processed in the last file processed. FS Input field separator regular expression; a space character by default. NF The number of fields in the current record.

Inside a BEGIN action, the use of NF is unde-

fined unless a getline function without a var argument is executed previously. Inside an END action, NF retains the value it had for the last record read, unless a subsequent, redirected,

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getline function without a var argument is per-

formed prior to entering the END action. NR The ordinal number of the current record from the start of input. Inside a BEGIN action the value is zero. Inside an END action the value is the number of the last record processed. OFMT The printf format for converting numbers to

strings in output statements "%.6g" by default.

The result of the conversion is unspecified if

the value of OFMT is not a floating-point format

specification. OFS The print statement output field separator; a space character by default. ORS The print output record separator; a newline character by default. LENGTH The length of the string matched by the match function. RS The first character of the string value of RS is the input record separator; a newline character

by default. If RS contains more than one charac-

ter, the results are unspecified. If RS is null, then records are separated by sequences of one or more blank lines. Leading or trailing blank

lines do not produce empty records at the begin-

ning or end of input, and the field separator is always newline, no matter what the value of FS. RSTART The starting position of the string matched by the match function, numbering from 1. This is always equivalent to the return value of the match function.

SUBSEP The subscript separator string for multi-

dimensional arrays. The default value is \034. /usr/xpg4/bin/awk

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The following variable is supported for /usr/xpg4/bin/awk only: CONVFMT The printf format for converting numbers to strings (except for output statements, where OFMT

is used). The default is %.6g.

Regular Expressions

The /usr/xpg4/bin/nawk utility makes use of the extended

regular expression notation (see regex(5)) except that it

allows the use of C-language conventions to escape special

characters within the EREs, namely \\, \a, \b, \f, \n, \r, \t, \v, and those specified in the following table. These escape sequences are recognized both inside and outside

bracket expressions. Records need not be separated by new-

line characters and string constants can contain newline

characters, so even the \n sequence is valid in nawk EREs.

Using a slash character within the regular expression requires escaping as shown in the table below: Escape Sequence Description Meaning

______________________________________________________________________

\" Backslash quotation-mark Quotation-mark character

______________________________________________________________________

\/ Backslash slash Slash character

______________________________________________________________________

\ddd A backslash character The character encoded by

followed by the longest the one-, two- or

sequence of one, two, or three-digit octal

three octal-digit char- integer. Multi-byte

acters (01234567). If characters require mul-

all of the digits are 0, tiple, concatenated (that is, representation escape sequences, of the NULL character), including the leading \

the behavior is unde- for each byte.

fined.

______________________________________________________________________

\c A backslash character Undefined

followed by any charac-

ter not described in this table or special characters (\\, \a, \b, \f, \n, \r, \t, \v). A regular expression can be matched against a specific field

or string by using one of the two regular expression match-

ing operators, ~ and !~. These operators interpret their

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right-hand operand as a regular expression and their left-

hand operand as a string. If the regular expression matches the string, the ~ expression evaluates to the value 1, and the !~ expression evaluates to the value 0. If the regular expression does not match the string, the ~ expression evaluates to the value 0, and the !~ expression evaluates to

the value 1. If the right-hand operand is any expression

other than the lexical token ERE, the string value of the expression is interpreted as an extended regular expression, including the escape conventions described above. Notice that these same escape conventions also are applied in the determining the value of a string literal (the lexical token STRING), and is applied a second time when a string literal is used in this context. When an ERE token appears as an expression in any context

other than as the right-hand of the ~ or !~ operator or as

one of the built-in function arguments described below, the

value of the resulting expression is the equivalent of:

$0 ~ /ere/

The ere argument to the gsub, match, sub functions, and the fs argument to the split function (see String Functions) is interpreted as extended regular expressions. These can be

either ERE tokens or arbitrary expressions, and are inter-

preted in the same manner as the right-hand side of the ~ or

!~ operator. An extended regular expression can be used to separate

fields by using the -F ERE option or by assigning a string

containing the expression to the built-in variable FS. The

default value of the FS variable is a single space charac-

ter. The following describes FS behavior: 1. If FS is a single character: o If FS is the space character, skip leading and trailing blank characters; fields are delimited by sets of one or more blank characters. o Otherwise, if FS is any other character c, fields are delimited by each single occurrence of c. 2. Otherwise, the string value of FS is considered to be an extended regular expression. Each occurrence of a sequence matching the extended regular

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expression delimits fields.

Except in the gsub, match, split, and sub built-in func-

tions, regular expression matching is based on input records. That is, record separator characters (the first

character of the value of the variable RS, a newline charac-

ter by default) cannot be embedded in the expression, and no expression matches the record separator character. If the

record separator is not a newline character, newline charac-

ters embedded in the expression can be matched. In those

four built-in functions, regular expression matching are

based on text strings. So, any character (including the new-

line character and the record separator) can be embedded in

the pattern and an appropriate pattern matches any charac-

ter. However, in all nawk regular expression matching, the

use of one or more NULL characters in the pattern, input record or text string produces undefined results. Patterns A pattern is any valid expression, a range specified by two expressions separated by comma, or one of the two special patterns BEGIN or END. Special Patterns

The nawk utility recognizes two special patterns, BEGIN and

END. Each BEGIN pattern is matched once and its associated action executed before the first record of input is read (except possibly by use of the getline function in a prior BEGIN action) and before command line assignment is done. Each END pattern is matched once and its associated action executed after the last record of input has been read. These two patterns have associated actions. BEGIN and END do not combine with other patterns. Multiple BEGIN and END patterns are allowed. The actions associated with the BEGIN patterns are executed in the order specified in the program, as are the END actions. An END pattern can precede a BEGIN pattern in a program.

If an nawk program consists of only actions with the pattern

BEGIN, and the BEGIN action contains no getline function,

nawk exits without reading its input when the last statement

in the last BEGIN action is executed. If an nawk program

consists of only actions with the pattern END or only actions with the patterns BEGIN and END, the input is read before the statements in the END actions are executed. Expression Patterns

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An expression pattern is evaluated as if it were an expres-

sion in a Boolean context. If the result is true, the pat-

tern is considered to match, and the associated action (if any) is executed. If the result is false, the action is not executed. Pattern Ranges A pattern range consists of two expressions separated by a comma. In this case, the action is performed for all records between a match of the first expression and the following match of the second expression, inclusive. At this point, the pattern range can be repeated starting at input records subsequent to the end of the matched range. Actions An action is a sequence of statements. A statement can be one of the following: if ( expression ) statement [ else statement ] while ( expression ) statement do statement while ( expression ) for ( expression ; expression ; expression ) statement for ( var in array ) statement

delete array[subscript] #delete an array element

break continue { [ statement ] ... }

expression # commonly variable = expression

print [ expression-list ] [ >expression ]

printf format [ ,expression-list ] [ >expression ]

next # skip remaining patterns on this input line

exit [expr] # skip the rest of the input; exit status is expr

return [expr] Any single statement can be replaced by a statement list

enclosed in braces. The statements are terminated by new-

line characters or semicolons, and are executed sequentially in the order that they appear. The next statement causes all further processing of the

current input record to be abandoned. The behavior is unde-

fined if a next statement appears or is invoked in a BEGIN or END action. The exit statement invokes all END actions in the order in which they occur in the program source and then terminate the program without reading further input. An exit statement inside an END action terminates the program without further

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execution of END actions. If an expression is specified in an exit statement, its numeric value is the exit status of

nawk, unless subsequent errors are encountered or a subse-

quent exit statement with an expression is executed. Output Statements Both print and printf statements write to standard output by default. The output is written to the location specified by

output_redirection if one is supplied, as follows:

> expression>> expression| expression In all cases, the expression is evaluated to produce a string that is used as a full pathname to write into (for > or >>) or as a command to be executed (for |). Using the first two forms, if the file of that name is not currently open, it is opened, creating it if necessary and using the first form, truncating the file. The output then is appended to the file. As long as the file remains open, subsequent calls in which expression evaluates to the same string value simply appends output to the file. The file remains open until the close function, which is called with an expression that evaluates to the same string value. The third form writes output onto a stream piped to the input of a command. The stream is created if no stream is currently open with the value of expression as its command name. The stream created is equivalent to one created by a call to the popen(3C) function with the value of expression

as the command argument and a value of w as the mode argu-

ment. As long as the stream remains open, subsequent calls in which expression evaluates to the same string value writes output to the existing stream. The stream remains open until the close function is called with an expression that evaluates to the same string value. At that time, the stream is closed as if by a call to the pclose function.

These output statements take a comma-separated list of

expression s referred in the grammar by the non-terminal

symbols expr_list, print_expr_list or print_expr_list_opt.

This list is referred to here as the expression list, and each member is referred to as an expression argument. The print statement writes the value of each expression argument onto the indicated output stream separated by the current output field separator (see variable OFS above), and terminated by the output record separator (see variable ORS

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above). All expression arguments is taken as strings, being converted if necessary; with the exception that the printf format in OFMT is used instead of the value in CONVFMT. An empty expression list stands for the whole input record

($0).

The printf statement produces output based on a notation similar to the File Format Notation used to describe file formats in this document Output is produced as specified with the first expression argument as the string format and subsequent expression arguments as the strings arg1 to argn, inclusive, with the following exceptions: 1. The format is an actual character string rather

than a graphical representation. Therefore, it can-

not contain empty character positions. The space character in the format string, in any context other than a flag of a conversion specification, is treated as an ordinary character that is copied to the output. 2. If the character set contains a Delta character and that character appears in the format string, it is treated as an ordinary character that is copied to the output. 3. The escape sequences beginning with a backslash

character is treated as sequences of ordinary char-

acters that are copied to the output. Note that these same sequences is interpreted lexically by

nawk when they appear in literal strings, but they

is not treated specially by the printf statement. 4. A field width or precision can be specified as the * character instead of a digit string. In this case the next argument from the expression list is fetched and its numeric value taken as the field width or precision.

5. The implementation does not precede or follow out-

put from the d or u conversion specifications with blank characters not specified by the format string. 6. The implementation does not precede output from the o conversion specification with leading zeros not specified by the format string. 7. For the c conversion specification: if the argument has a numeric value, the character whose encoding is that value is output. If the value is zero or

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is not the encoding of any character in the charac-

ter set, the behavior is undefined. If the argu-

ment does not have a numeric value, the first char-

acter of the string value is output; if the string does not contain any characters the behavior is undefined. 8. For each conversion specification that consumes an argument, the next expression argument is evaluated. With the exception of the c conversion, the value is converted to the appropriate type for the conversion specification. 9. If there are insufficient expression arguments to satisfy all the conversion specifications in the format string, the behavior is undefined. 10. If any character sequence in the format string

begins with a % character, but does not form a

valid conversion specification, the behavior is unspecified.

Both print and printf can output at least {LINE_MAX} bytes.

Functions

The nawk language has a variety of built-in functions:

arithmetic, string, input/output and general. Arithmetic Functions The arithmetic functions, except for int, are based on the ISO C standard. The behavior is undefined in cases where the ISO C standard specifies that an error be returned or that the behavior is undefined. Although the grammar permits

built-in functions to appear with no arguments or

parentheses, unless the argument or parentheses are indi-

cated as optional in the following list (by displaying them within the [ ] brackets), such use is undefined. atan2(y,x) Return arctangent of y/x. cos(x) Return cosine of x, where x is in radians. sin(x) Return sine of x, where x is in radians. exp(x) Return the exponential function of x.

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log(x) Return the natural logarithm of x. sqrt(x) Return the square root of x. int(x) Truncate its argument to an integer. It is truncated toward 0 when x > 0. rand() Return a random number n, such that 0 < n < 1. srand([expr]) Set the seed value for rand to expr or use the time of day if expr is omitted. The previous seed value is returned. String Functions

The string functions in the following list shall be sup-

ported. Although the grammar permits built-in functions to

appear with no arguments or parentheses, unless the argument or parentheses are indicated as optional in the following list (by displaying them within the [ ] brackets), such use is undefined. gsub(ere,repl[,in]) Behave like sub (see below), except that it replaces all

occurrences of the regular expression (like the ed util-

ity global substitute) in $0 or in the in argument, when

specified. index(s,t) Return the position, in characters, numbering from 1, in string s where string t first occurs, or zero if it does not occur at all. length[([s])] Return the length, in characters, of its argument taken

as a string, or of the whole record, $0, if there is no

argument. match(s,ere) Return the position, in characters, numbering from 1, in

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string s where the extended regular expression ere occurs, or zero if it does not occur at all. RSTART is set to the starting position (which is the same as the returned value), zero if no match is found; RLENGTH is

set to the length of the matched string, -1 if no match

is found. split(s,a[,fs]) Split the string s into array elements a[1], a[2], ..., a[n], and return n. The separation is done with the

extended regular expression fs or with the field separa-

tor FS if fs is not given. Each array element has a string value when created. If the string assigned to any

array element, with any occurrence of the decimal-point

character from the current locale changed to a period character, would be considered a numeric string; the array element also has the numeric value of the numeric string. The effect of a null string as the value of fs is unspecified. sprintf(fmt,expr,expr,...) Format the expressions according to the printf format given by fmt and return the resulting string. sub(ere,repl[,in]) Substitute the string repl in place of the first instance of the extended regular expression ERE in string in and return the number of substitutions. An ampersand ( & ) appearing in the string repl is replaced

by the string from in that matches the regular expres-

sion. An ampersand preceded with a backslash ( \ ) is interpreted as the literal ampersand character. An occurrence of two consecutive backslashes is interpreted as just a single literal backslash character. Any other occurrence of a backslash (for example, preceding any

other character) is treated as a literal backslash char-

acter. If repl is a string literal, the handling of the ampersand character occurs after any lexical processing,

including any lexical backslash escape sequence process-

ing. If in is specified and it is not an lvalue the

behavior is undefined. If in is omitted, nawk uses the

current record ($0) in its place.

substr(s,m[,n])

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Return the at most n-character substring of s that

begins at position m, numbering from 1. If n is missing, the length of the substring is limited by the length of the string s. tolower(s) Return a string based on the string s. Each character in

s that is an upper-case letter specified to have a

tolower mapping by the LC_CTYPE category of the current

locale is replaced in the returned string by the lower-

case letter specified by the mapping. Other characters in s are unchanged in the returned string. toupper(s) Return a string based on the string s. Each character in

s that is a lower-case letter specified to have a

toupper mapping by the LC_CTYPE category of the current

locale is replaced in the returned string by the upper-

case letter specified by the mapping. Other characters in s are unchanged in the returned string. All of the preceding functions that take ERE as a parameter expect a pattern or a string valued expression that is a regular expression as defined below.

Input/Output and General Functions The input/output and general functions are: close(expression) Close the file or pipe opened by a print or printf statement or a call to getline with the same

string-valued expression. If the

close was successful, the func-

tion returns 0; otherwise, it

returns non-zero.

expression|getline[var] Read a record of input from a stream piped from the output of a command. The stream is created if no stream is currently open with the value of expression as its command name. The stream created is equivalent to one created by a call to the popen function with the value of expression as the

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command argument and a value of r as the mode argument. As long as

the stream remains open, subse-

quent calls in which expression evaluates to the same string value reads subsequent records from the file. The stream remains open until the close function is called with an expression that evaluates to the same string value. At that time, the stream is closed as if by a call to the

pclose function. If var is miss-

ing, $0 and NF is set. Otherwise,

var is set. The getline operator can form ambiguous constructs when there are operators that are not in

parentheses (including concaten-

ate) to the left of the | (to the

beginning of the expression con-

taining getline). In the context

of the $ operator, | behaves as

if it had a lower precedence than

$. The result of evaluating other

operators is unspecified, and all

such uses of portable applica-

tions must be put in parentheses properly.

getline Set $0 to the next input

record from the current input file. This form of getline

sets the NF, NR, and FNR vari-

ables. getline var Set variable var to the next input record from the current

input file. This form of get-

line sets the FNR and NR vari-

ables. getline [var] < expression Read the next record of input

from a named file. The expres-

sion is evaluated to produce a string that is used as a full pathname. If the file of that name is not currently open, it

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is opened. As long as the

stream remains open, subse-

quent calls in which expres-

sion evaluates to the same string value reads subsequent records from the file. The file remains open until the close function is called with an expression that evaluates to the same string value. If

var is missing, $0 and NF is

set. Otherwise, var is set. The getline operator can form ambiguous constructs when there are binary operators that are not in parentheses (including concatenate) to the right of the < (up to the end of the expression containing the getline). The result of evaluating such a construct is unspecified, and all such uses of portable applications must

be put in parentheses prop-

erly. system(expression) Execute the command given by expression in a manner equivalent to the system(3C) function and return the exit status of the command. All forms of getline return 1 for successful input, 0 for

end of file, and -1 for an error.

Where strings are used as the name of a file or pipeline, the strings must be textually identical. The terminology ``same string value'' implies that ``equivalent strings'', even those that differ only by space characters, represent different files.

User-defined Functions

The nawk language also provides user-defined functions. Such

functions can be defined as: function name(args,...) { statements }

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A function can be referred to anywhere in an nawk program;

in particular, its use can precede its definition. The scope of a function is global. Function arguments can be either scalars or arrays; the

behavior is undefined if an array name is passed as an argu-

ment that the function uses as a scalar, or if a scalar expression is passed as an argument that the function uses as an array. Function arguments are passed by value if scalar and by reference if array name. Argument names are local to the function; all other variable names are global. The same name is not used as both an argument name and as

the name of a function or a special nawk variable. The same

name must not be used both as a variable name with global scope and as the name of a function. The same name must not be used within the same scope both as a scalar variable and as an array. The number of parameters in the function definition need not match the number of parameters in the function call. Excess formal parameters can be used as local variables. If fewer arguments are supplied in a function call than are in the function definition, the extra parameters that are used in the function body as scalars are initialized with a string value of the null string and a numeric value of zero, and the extra parameters that are used in the function body as arrays are initialized as empty arrays. If more arguments are supplied in a function call than are in the function definition, the behavior is undefined. When invoking a function, no white space can be placed

between the function name and the opening parenthesis. Func-

tion calls can be nested and recursive calls can be made upon functions. Upon return from any nested or recursive function call, the values of all of the calling function's parameters are unchanged, except for array parameters passed by reference. The return statement can be used to return a value. If a return statement appears outside of a function definition, the behavior is undefined. In the function definition, newline characters are optional

before the opening brace and after the closing brace. Func-

tion definitions can appear anywhere in the program where a

pattern-action pair is allowed.

USAGE

The index, length, match, and substr functions should not be confused with similar functions in the ISO C standard; the

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nawk versions deal with characters, while the ISO C standard

deals with bytes.

Because the concatenation operation is represented by adja-

cent expressions rather than an explicit operator, it is often necessary to use parentheses to enforce the proper evaluation precedence.

See largefile(5) for the description of the behavior of nawk

when encountering files greater than or equal to 2 Gbyte (2^31 bytes).

EXAMPLES

The nawk program specified in the command line is most

easily specified within single-quotes (for example, 'pro-

gram') for applications using sh, because nawk programs com-

monly contain characters that are special to the shell,

including double-quotes. In the cases where a nawk program

contains single-quote characters, it is usually easiest to

specify most of the program as strings within single-quotes

concatenated by the shell with quoted single-quote charac-

ters. For example:

nawk '/'\''/ { print "quote:", $0 }'

prints all lines from the standard input containing a

single-quote character, prefixed with quote:.

The following are examples of simple nawk programs:

Example 1 Write to the standard output all input lines for which field 3 is greater than 5:

$3 > 5

Example 2 Write every tenth line:

(NR % 10) == 0

Example 3 Write any line with a substring matching the regu-

lar expression:

/(G|D)(2[0-9][[:alpha:]]*)/

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Example 4 Print any line with a substring containing a G or D, followed by a sequence of digits and characters: This example uses character classes digit and alpha to match

language-independent digit and alphabetic characters,

respectively. /(G|D)([[:digit:][:alpha:]]*)/ Example 5 Write any line in which the second field matches the regular expression and the fourth field does not:

$2 ~ /xyz/ && $4 !~ /xyz/

Example 6 Write any line in which the second field contains a backslash:

$2 ~ /\\/

Example 7 Write any line in which the second field contains a backslash (alternate method): Notice that backslash escapes are interpreted twice, once in lexical processing of the string and once in processing the regular expression.

$2 ~ "\\\\"

Example 8 Write the second to the last and the last field in each line, separating the fields by a colon:

{OFS=":";print $(NF-1), $NF}

Example 9 Write the line number and number of fields in each line:

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The three strings representing the line number, the colon and the number of fields are concatenated and that string is written to standard output. {print NR ":" NF} Example 10 Write lines longer than 72 characters:

{length($0) > 72}

Example 11 Write first two fields in opposite order separated by the OFS:

{ print $2, $1 }

Example 12 Same, with input fields separated by comma or space and tab characters, or both: BEGIN { FS = ",[\t]*|[\t]+" }

{ print $2, $1 }

Example 13 Add up first column, print sum and average:

{s += $1 }

END {print "sum is ", s, " average is", s/NR} Example 14 Write fields in reverse order, one per line (many lines out for each line in):

{ for (i = NF; i > 0; --i) print $i }

Example 15 Write all lines between occurrences of the strings "start" and "stop": /start/, /stop/

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Example 16 Write all lines whose first field is different from the previous one:

$1 != prev { print; prev = $1 }

Example 17 Simulate the echo command: BEGIN { for (i = 1; i < ARGC; ++i)

printf "%s%s", ARGV[i], i==ARGC-1?"\n":""

} Example 18 Write the path prefixes contained in the PATH environment variable, one per line: BEGIN { n = split (ENVIRON["PATH"], path, ":") for (i = 1; i <= n; ++i) print path[i] } Example 19 Print the file "input", filling in page numbers starting at 5: If there is a file named input containing page headers of the form

Page#

and a file named program that contains

/Page/{ $2 = n++; }

{ print } then the command line

nawk -f program n=5 input

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prints the file input, filling in page numbers starting at 5. ENVIRONMENT VARIABLES See environ(5) for descriptions of the following environment

variables that affect execution: LC_COLLATE, LC_CTYPE,

LC_MESSAGES, and NLSPATH.

LC_NUMERIC Determine the radix character used when inter-

preting numeric input, performing conversions

between numeric and string values and format-

ting numeric output. Regardless of locale, the

period character (the decimal-point character

of the POSIX locale) is the decimal-point

character recognized in processing awk pro-

grams (including assignments in command-line

arguments). EXIT STATUS The following exit values are returned: 0 All input files were processed successfully. >0 An error occurred. The exit status can be altered within the program by using an exit expression.

ATTRIBUTES

See attributes(5) for descriptions of the following attri-

butes:

/usr/bin/nawk

____________________________________________________________

| ATTRIBUTE TYPE | ATTRIBUTE VALUE |

|_____________________________|_____________________________|

| Availability | SUNWcs |

|_____________________________|_____________________________|

/usr/xpg4/bin/awk

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____________________________________________________________

| ATTRIBUTE TYPE | ATTRIBUTE VALUE |

|_____________________________|_____________________________|

| Availability | SUNWxcu4 |

|_____________________________|_____________________________|

be accessed, nawk writes a diagnostic message to standard

error and terminate without any further action. If the program specified by either the program operand or a

progfile operand is not a valid nawk program (as specified

in EXTENDED DESCRIPTION), the behavior is undefined.

NOTES Input white space is not preserved on output if fields are involved. There are no explicit conversions between numbers and strings. To force an expression to be treated as a number

add 0 to it; to force it to be treated as a string concaten-

ate the null string ("") to it.

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