illumos: manual page: regcmp.3c

REGCMP(3C) Standard C Library Functions REGCMP(3C)

NAME

regcmp, regex - compile and execute regular expression

SYNOPSIS

#include <libgen.h>

char *regcmp(const char *string1, /* char *string2 */ ...,
int /*(char*)0*/);

char *regex(const char *re, const char *subject,
/* char *ret0 */ ...);

extern char *__loc1;

DESCRIPTION

The regcmp() function compiles a regular expression (consisting of the
concatenated arguments) and returns a pointer to the compiled form. The
malloc(3C) function is used to create space for the compiled form. It is
the user's responsibility to free unneeded space so allocated. A NULL
return from regcmp() indicates an incorrect argument. regcmp(1) has been
written to generally preclude the need for this routine at execution
time.

The regex() function executes a compiled pattern against the subject
string. Additional arguments are passed to receive values back. The
regex() function returns NULL on failure or a pointer to the next
unmatched character on success. A global character pointer __loc1 points
to where the match began. The regcmp() and regex() functions were mostly
borrowed from the editor ed(1); however, the syntax and semantics have
been changed slightly. The following are the valid symbols and associated
meanings.

[]*.^
This group of symbols retains its meaning as described
on the regexp(7) manual page.

$
Matches the end of the string; \n matches a newline.

-
Within brackets the minus means through. For example,
[a-z] is equivalent to [abcd...xyz]. The - can appear
as itself only if used as the first or last character.
For example, the character class expression []-]
matches the characters ] and -.

+
A regular expression followed by + means one or more
times. For example, [0-9]+ is equivalent to
[0-9][0-9]*.

{m} {m,} {m,u}
Integer values enclosed in {} indicate the number of
times the preceding regular expression is to be
applied. The value m is the minimum number and u is a
number, less than 256, which is the maximum. If only m
is present (that is, {m}), it indicates the exact
number of times the regular expression is to be
applied. The value {m,} is analogous to {m,infinity}.
The plus (+) and star (*) operations are equivalent to
{1,} and {0,} respectively.

( ... )$n
The value of the enclosed regular expression is to be
returned. The value will be stored in the (n+1)th
argument following the subject argument. At most, ten
enclosed regular expressions are allowed. The regex()
function makes its assignments unconditionally.

( ... )
Parentheses are used for grouping. An operator, for
example, *, +, {}, can work on a single character or a
regular expression enclosed in parentheses. For
example, (a*(cb+)*)$0. By necessity, all the above
defined symbols are special. They must, therefore, be
escaped with a \ (backslash) to be used as themselves.

EXAMPLES

Example 1: Example matching a leading newline in the subject string.

The following example matches a leading newline in the subject string
pointed at by cursor.

char *cursor, *newcursor, *ptr;
...
newcursor = regex((ptr = regcmp("^\n", (char *)0)), cursor);
free(ptr);

The following example matches through the string Testing3 and returns the
address of the character after the last matched character (the ``4'').
The string Testing3 is copied to the character array ret0.

char ret0[9];
char *newcursor, *name;
...
name = regcmp("([A-Za-z][A-za-z0-9]{0,7})$0", (char *)0);
newcursor = regex(name, "012Testing345", ret0);

The following example applies a precompiled regular expression in file.i
(see regcmp(1)) against string.

#include "file.i"
char *string, *newcursor;
...
newcursor = regex(name, string);

ATTRIBUTES

NOTES

The user program may run out of memory if regcmp() is called iteratively
without freeing the vectors no longer required.

When compiling multithreaded applications, the _REENTRANT flag must be
defined on the compile line. This flag should only be used in
multithreaded applications.

November 14, 2002 REGCMP(3C)