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 (con-
sisting 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 respon-
sibility 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 bor-
rowed from the editor ed(1); however, the syntax and seman-
tics 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(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 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 exam-
ple, (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 sub-
ject 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 expres-
sion in file.i (see regcmp(1)) against string.
#include "file.i"
char *string, *newcursor;
...
newcursor = regex(name, string);
FILES
/usr/ccs/lib/libgen.a
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| MT-Level | MT-Safe |
|_____________________________|_____________________________|
SEE ALSO
ed(1), regcmp(1), malloc(3C), attributes(5), regexp(5)
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.
Man(1) output converted with
man2html