regcmp(3G) regcmp(3G)
NAME
regcmp, regex - compile and execute regular expression
SYNOPSIS
cc [flag . . . ] file . . . -lgen [library] . . .
#include <libgen.h>
char *regcmp (const char *string1 [, char *string2, ...],
(char *)0);
char *regex (const char *re, const char *subject
[, char *ret0, ...]);
extern char *_ _loc1;
DESCRIPTION
regcmp compiles a regular expression (consisting of the
concatenated arguments) and returns a pointer to the compiled
form. malloc(3C) 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. regcmp
is located in library libform.
regex executes a compiled pattern against the subject string.
Additional arguments are passed to receive values back. regex
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. regcmp and regex 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.
[]*.^ These symbols retain their meaning in ed(1).
$ 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]*.
Copyright 1994 Novell, Inc. Page 1
regcmp(3G) regcmp(3G)
{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.
regex 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
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);
Copyright 1994 Novell, Inc. Page 2
regcmp(3G) regcmp(3G)
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);
REFERENCES
ed(1), malloc(3C), regcmp(1)
NOTICES
The user program may run out of memory if regcmp is called
iteratively without freeing the vectors no longer required.
Copyright 1994 Novell, Inc. Page 3