REGCMP(3C)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 sym‐
bols and associated meanings.
[]*.^
This group of symbols retains its meaning as
described on the regexp(5) 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 charac‐
ter. 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 them‐
selves.
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
See attributes(5) for descriptions of the following attributes:
┌───────────────┬─────────────────┐
│ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├───────────────┼─────────────────┤
│MT-Level │ MT-Safe │
└───────────────┴─────────────────┘
SEE ALSOed(1), regcmp(1), malloc(3C), attributes(5), regexp(5)NOTES
The user program may run out of memory if regcmp() is called itera‐
tively 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 multi‐
threaded applications.
Nov 14, 2002 REGCMP(3C)
