regcmp(3X) SDK R4.11 regcmp(3X)
NAME
regcmp, regex - compile and execute regular expression
SYNOPSIS
char *regcmp (string1 [, string2, ..., stringn], (char *)0)
char *string1, *string2, ..., *stringn;
char *regex (re, subject[, ret0, ...])
char *re, *subject, *ret0, ...;
extern char *__loc1;
DESCRIPTION
regcmp and regex implement extended regular expressions, without
support for internationalization features. See regexpr(3C) as well.
regcmp compiles a regular expression and returns a pointer to the
compiled form. Malloc(3C) is used to create space for the vector.
You must 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. If regcmp(1) is used, the running of
regcmp(1) and regex must occur in the same locale (see
setlocale(3C)).
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 their associated meanings.
[]*.^ These symbols retain their current meaning.
$ Matches the end of the string; \n matches a new-line. The
$ symbol must be the last character of the last stringn
argument given to regcmp, or the $ symbol is taken as a
literal '$' character (ie., it is given no special meaning
at all).
- Within brackets the minus means through. For example,
[a-z] is equivalent to [abcd...xyz]. The - can appear as
itself only if used as the first or last character. For
example, the character class expression []-] matches the
characters ]\f4and\f1-.
+ A regular expression followed by + means one or more times.
For example, [0-9]+ is equivalent to [0-9][0-9]*.
{m} {m,} {m,u}
Integer values enclosed in {} indicate the number of times
the preceding regular expression is to be applied. The
value m is the minimum number and u is a number, less than
256, which is the maximum. If only m is present (e.g.,
{m}), it indicates the exact number of times the regular
expression is to be applied. The value {m,} is analogous
to {m,infinity}. The plus (+) and star (*) operations are
equivalent to {1,} and {0,} respectively.
( ... )$n The value of the enclosed regular expression is 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, e.g., *,
+, {}, can work on a single character or a regular
expression enclosed in parentheses. For example,
(a*(cb+)*)$0.
All of these symbols are special. They must, therefore, be escaped
to be used as themselves (except in the case of the $ symbol which is
explained above).
regcmp and regex do not support the following international features
in regular expressions that are described in ed(1):
[.ch.] multi-character collation symbol
[=c=] collation-order equivalence class
[:alpha:] character class
Moreover, character ranges such as [a-j] are interpreted by simply
comparing the numeric values of the character bytes, not by using
collation ordering information.
EXAMPLES
Example 1:
char *cursor, *newcursor, *ptr;
...
newcursor = regex((ptr = regcmp("^\n", 0)), cursor);
free(ptr);
This example will match a leading new-line in the subject string that
the cursor points to.
Example 2:
char ret0[9];
char *newcursor, *name;
...
name = regcmp("([A-Za-z][A-za-z0-9_]{0,7})$0", 0);
newcursor = regex(name, "123Testing321", ret0);
This example matches through the string Testing3 and returns the
address of the character after the last matched character
(cursor+11). The string Testing3 is copied to the character array
ret0.
Example 3:
char ret0[9];
char *newcursor, *name;
...
name = regcmp("(a+)$0", "$", (char *) 0);
newcursor = regex(name, "aabcaaa", ret0);
This is an example of how the $ symbol should be used to anchor
regular expressions. This example matches through the string 'aaa'
and returns the address of the character after the last matched
character. The string 'aaa' is copied to the character array ret0.
Example 4:
#include "file.i"
char *string, *newcursor;
...
newcursor = regex(name, string);
This example applies a precompiled regular expression in file.i (see
regcmp(1)) against string.
This routine is kept in /lib/libPW.a.
SEE ALSO
regcmp(3G), malloc(3C).
ed(1), regcmp(1)
CAUTION
The user program may run out of memory if regcmp is called
iteratively without freeing the vectors no longer required.
This regcmp in /lib/libPW.a has been replaced by the one in
/lib/libgen.a. See regcmp(3G).
Licensed material--property of copyright holder(s)