regcmp(3G)
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).
$-
Matches the end of the string; \n matches a newline.
--
Within brackets the minus means
through.
For example,
[a-z]
is equivalent to
[abcd...xyz].
The - can
appear as itself only if used as the
first or last character.
For example, the character class expression
[]-]
matches the characters
] and -.
+-
A regular expression followed by + means
one or more times.
For example,
[0-9]+
is equivalent to
[0-9][0-9].
{m} {m,} {m,u}-
Integer values enclosed in {} indicate the
number of times the preceding regular expression is to be applied.
The value
m
is the minimum number and
u
is a number, less than 256, which is the maximum.
If only
m
is present (that is, {m}),
it indicates the exact number of times the regular
expression is to be applied.
The value
{m,} is analogous to {m,infinity}.
The plus (+) and star () operations are
equivalent to {1,} and {0,} respectively.
( ... )$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);
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.
© 2004 The SCO Group, Inc. All rights reserved.
UnixWare 7 Release 7.1.4 - 25 April 2004