Standards, Environments, and Macros regexp(5)
NAME
regexp, compile, step, advance - simple regular expression
compile and match routines
SYNOPSIS
#define INIT declarations
#define GETC(void) getc code
#define PEEKC(void) peekc code
#define UNGETC(void) ungetc code
#define RETURN(ptr) return code
#define ERROR(val) error code
extern char *loc1, *loc2, *locs;#include
char *compile(char *instring, char *expbuf, const char *endfug, int eof);
int step(const char *string, const char *expbuf); int advance(const char *string, const char *expbuf);DESCRIPTION
Regular Expressions (REs) provide a mechanism to select specific strings from a set of character strings. The SimpleRegular Expressions described below differ from the Inter-
nationalized Regular Expressions described on the regex(5) manual page in the following ways: o only Basic Regular Expressions are supportedo the Internationalization features-character class,
equivalence class, and multi-character collation-
are not supported.The functions step(), advance(), and compile() are general
purpose regular expression matching routines to be used in programs that perform regular expression matching. These functions are defined by theheader. The functions step() and advance() do pattern matching given a character string and a compiled regular expression as
input.The function compile() takes as input a regular expression
as defined below and produces a compiled expression that can
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Standards, Environments, and Macros regexp(5) be used with step() or advance(). Basic Regular Expressions A regular expression specifies a set of character strings. A member of this set of strings is said to be matched by the regular expression. Some characters have special meaning when used in a regular expression; other characters stand for themselves.The following one-character REs match a single character:
1.1 An ordinary character ( not one of those discussed in1.2 below) is a one-character RE that matches itself.
1.2 A backslash (\) followed by any special character isa one-character RE that matches the special character
itself. The special characters are: a. ., *, [, and \ (period, asterisk, left square bracket, and backslash, respectively), which are always special, except when they appear within square brackets ([]; see 1.4 below). b. ^ (caret or circumflex), which is special at the beginning of an entire RE (see 4.1 and 4.3 below), or when it immediately follows the left of a pair of square brackets ([]) (see 1.4 below).c. $ (dollar sign), which is special at the end of
an entire RE (see 4.2 below). d. The character used to bound (that is, delimit) an entire RE, which is special for that RE (for example, see how slash (/) is used in the g command, below.)1.3 A period (.) is a one-character RE that matches any
character except new-line.
1.4 A non-empty string of characters enclosed in square
brackets ([]) is a one-character RE that matches any
one character in that string. If, however, the first character of the string is a circumflex (^), theSunOS 5.11 Last change: 20 May 2002 2
Standards, Environments, and Macros regexp(5)one-character RE matches any character except new-
line and the remaining characters in the string. The ^ has this special meaning only if it occurs first inthe string. The minus (-) may be used to indicate a
range of consecutive characters; for example, [0-9]
is equivalent to [0123456789]. The - loses this spe-
cial meaning if it occurs first (after an initial ^, if any) or last in the string. The right square bracket (]) does not terminate such a string when it is the first character within it (after an initial ^,if any); for example, []a-f] matches either a right
square bracket (]) or one of the ASCII letters a through f inclusive. The four characters listed in 1.2.a above stand for themselves within such a string of characters.The following rules may be used to construct REs from one-
character REs:2.1 A one-character RE is a RE that matches whatever the
one-character RE matches.
2.2 A one-character RE followed by an asterisk (*) is a
RE that matches 0 or more occurrences of the one-
character RE. If there is any choice, the longest leftmost string that permits a match is chosen.2.3 A one-character RE followed by \{m\}, \{m,\}, or
\{m,n\} is a RE that matches a range of occurrencesof the one-character RE. The values of m and n must
be non-negative integers less than 256; \{m\} matches
exactly m occurrences; \{m,\} matches at least m occurrences; \{m,n\} matches any number of occurrences between m and n inclusive. Whenever a choice exists, the RE matches as many occurrences as possible. 2.4 The concatenation of REs is a RE that matches theconcatenation of the strings matched by each com-
ponent of the RE. 2.5 A RE enclosed between the character sequences \( and \) is a RE that matches whatever the unadorned RE matches.SunOS 5.11 Last change: 20 May 2002 3
Standards, Environments, and Macros regexp(5)2.6 The expression \n matches the same string of charac-
ters as was matched by an expression enclosed between \( and \) earlier in the same RE. Here n is a digit;the sub-expression specified is that beginning with
the n-th occurrence of \( counting from the left. For
example, the expression ^\(.*\)\1$ matches a line
consisting of two repeated appearances of the same string. An RE may be constrained to match words. 3.1 \< constrains a RE to match the beginning of a stringor to follow a character that is not a digit, under-
score, or letter. The first character matching the RE must be a digit, underscore, or letter. 3.2 \> constrains a RE to match the end of a string or to precede a character that is not a digit, underscore, or letter. An entire RE may be constrained to match only an initial segment or final segment of a line (or both). 4.1 A circumflex (^) at the beginning of an entire RE constrains that RE to match an initial segment of a line.4.2 A dollar sign ($) at the end of an entire RE con-
strains that RE to match a final segment of a line.4.3 The construction ^entire RE$ constrains the entire RE
to match the entire line. The null RE (for example, //) is equivalent to the last RE encountered. Addressing with REs Addresses are constructed as follows: 1. The character "." addresses the current line.2. The character "$" addresses the last line of the
buffer.SunOS 5.11 Last change: 20 May 2002 4
Standards, Environments, and Macros regexp(5)3. A decimal number n addresses the n-th line of the
buffer. 4. 'x addresses the line marked with the mark namecharacter x, which must be an ASCII lower-case
letter (a-z). Lines are marked with the k command
described below. 5. A RE enclosed by slashes (/) addresses the firstline found by searching forward from the line fol-
lowing the current line toward the end of the buffer and stopping at the first line containing a string matching the RE. If necessary, the search wraps around to the beginning of the buffer and continues up to and including the current line, so that the entire buffer is searched. 6. A RE enclosed in question marks (?) addresses the first line found by searching backward from theline preceding the current line toward the begin-
ning of the buffer and stopping at the first line containing a string matching the RE. If necessary, the search wraps around to the end of the buffer and continues up to and including the current line. 7. An address followed by a plus sign (+) or a minussign (-) followed by a decimal number specifies
that address plus (respectively minus) the indi-
cated number of lines. A shorthand for .+5 is .5.8. If an address begins with + or -, the addition or
subtraction is taken with respect to the currentline; for example, -5 is understood to mean .-5.
9. If an address ends with + or -, then 1 is added to
or subtracted from the address, respectively. As a consequence of this rule and of Rule 8, immediatelyabove, the address - refers to the line preceding
the current line. (To maintain compatibility with earlier versions of the editor, the character ^ inaddresses is entirely equivalent to -.) Moreover,
trailing + and - characters have a cumulative
effect, so -- refers to the current line less 2.
10. For convenience, a comma (,) stands for the addresspair 1,$, while a semicolon (;) stands for the pair
.,$.
Characters With Special Meaning Characters that have special meaning except when they appear within square brackets ([]) or are preceded by \ are: ., *,[, \. Other special characters, such as $ have special
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Standards, Environments, and Macros regexp(5) meaning in more restricted contexts. The character ^ at the beginning of an expression permits a successful match only immediately after a newline, and thecharacter $ at the end of an expression requires a trailing
newline. Two characters have special meaning only when used withinsquare brackets. The character - denotes a range, [c-c],
unless it is just after the open bracket or before the clos-
ing bracket, [-c] or [c-] in which case it has no special
meaning. When used within brackets, the character ^ has the meaning complement of if it immediately follows the openbracket (example: [^c]); elsewhere between brackets (exam-
ple: [c^]) it stands for the ordinary character ^. The special meaning of the \ operator can be escaped only by preceding it with another \, for example \\. Macros Programs must have the following five macros declared beforethe #include
statement. These macros are used by the compile() routine. The macros GETC, PEEKC, and UNGETC
operate on the regular expression given as input to com-
pile(). GETC This macro returns the value of the next character (byte) in the regular expression pattern. Successive calls to GETC should return successive characters of the regular expression. PEEKC This macro returns the next character (byte)in the regular expression. Immediately suc-
cessive calls to PEEKC should return the same character, which should also be the next character returned by GETC. UNGETC This macro causes the argument c to be returned by the next call to GETC and PEEKC. No more than one character of pushback is ever needed and this character is guaranteed to be the last character read by GETC. The return value of the macro UNGETC(c) is always ignored.SunOS 5.11 Last change: 20 May 2002 6
Standards, Environments, and Macros regexp(5)RETURN(ptr) This macro is used on normal exit of the com-
pile() routine. The value of the argument ptr is a pointer to the character after the lastcharacter of the compiled regular expression.
This is useful to programs which have memory allocation to manage.ERROR(val) This macro is the abnormal return from the
compile() routine. The argument val is an
error number (see ERRORS below for meanings).
This call should never return.compile()
The syntax of the compile() routine is as follows:
compile(instring, expbuf, endbuf, eof)
The first parameter, instring, is never used explicitly bythe compile() routine but is useful for programs that pass
down different pointers to input characters. It is sometimes used in the INIT declaration (see below). Programs which call functions to input characters or have characters in an external array can pass down a value of (char *)0 for this parameter. The next parameter, expbuf, is a character pointer. Itpoints to the place where the compiled regular expression
will be placed. The parameter endbuf is one more than the highest addresswhere the compiled regular expression may be placed. If the
compiled expression cannot fit in (endbuf-expbuf) bytes, a
call to ERROR(50) is made.
The parameter eof is the character which marks the end of the regular expression. This character is usually a /. Each program that includes theheader file must have a #define statement for INIT. It is used for dependent
declarations and initializations. Most often it is used to set a register variable to point to the beginning of the regular expression so that this register variable can be used in the declarations for GETC, PEEKC, and UNGETC.SunOS 5.11 Last change: 20 May 2002 7
Standards, Environments, and Macros regexp(5) Otherwise it can be used to declare external variables thatmight be used by GETC, PEEKC and UNGETC. (See EXAMPLES
below.) step(), advance() The first parameter to the step() and advance() functions is a pointer to a string of characters to be checked for a match. This string should be null terminated.The second parameter, expbuf, is the compiled regular
expression which was obtained by a call to the function com-
pile().The function step() returns non-zero if some substring of
string matches the regular expression in expbuf and 0 ifthere is no match. If there is a match, two external charac-
ter pointers are set as a side effect to the call to step(). The variable loc1 points to the first character that matched the regular expression; the variable loc2 points to the character after the last character that matches the regular expression. Thus if the regular expression matches the entire input string, loc1 will point to the first character of string and loc2 will point to the null at the end of string.The function advance() returns non-zero if the initial sub-
string of string matches the regular expression in expbuf. If there is a match, an external character pointer, loc2, is set as a side effect. The variable loc2 points to the next character in string after the last character that matched.When advance() encounters a * or \{ \} sequence in the regu-
lar expression, it will advance its pointer to the string to be matched as far as possible and will recursively call itself trying to match the rest of the string to the rest of the regular expression. As long as there is no match, advance() will back up along the string until it finds a match or reaches the point in the string that initially matched the * or \{ \}. It is sometimes desirable to stop this backing up before the initial point in the string is reached. If the external character pointer locs is equal to the point in the string at sometime during the backing up process, advance() will break out of the loop that backs up and will return zero. The external variables circf, sed, and nbra are reserved.SunOS 5.11 Last change: 20 May 2002 8
Standards, Environments, and Macros regexp(5)EXAMPLES
Example 1 Using Regular Expression Macros and Calls The following is an example of how the regular expression macros and calls might be defined by an application program:#define INIT register char *sp = instring;
#define GETC() (*sp++)
#define PEEKC() (*sp)
#define UNGETC(c) (--sp)
#define RETURN(c) return;
#define ERROR(c) regerr()
#include
. . .(void) compile(*argv, expbuf, &expbuf[ESIZE],'\0');
. . . if (step(linebuf, expbuf)) succeed; DIAGNOSTICSThe function compile() uses the macro RETURN on success and
the macro ERROR on failure (see above). The functions step()
and advance() return non-zero on a successful match and zero
if there is no match. Errors are: 11 range endpoint too large. 16 bad number. 25 \ digit out of range. 36 illegal or missing delimiter. 41 no remembered search string. 42 \( \) imbalance. 43 too many \(.SunOS 5.11 Last change: 20 May 2002 9
Standards, Environments, and Macros regexp(5) 44 more than 2 numbers given in \{ \}. 45 } expected after \. 46 first number exceeds second in \{ \}. 49 [ ] imbalance. 50 regular expression overflow.SEE ALSO
regex(5)SunOS 5.11 Last change: 20 May 2002 10