REGCMP(3X) (Specialized Libraries) REGCMP(3X)
NAME
regcmp, regex - compile and execute regular expression
SYNOPSIS
char *regcmp (string1 [, string2, ...], (char *)0)
char *string1, *string2, ...;
char *regex (re, subject[, ret0, ...])
char *re, *subject, *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.
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 meaning in ed(1).
$ Matches the end of the string; \n matches a new-
line.
- 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
Page 1 May 1989
REGCMP(3X) (Specialized Libraries) REGCMP(3X)
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 (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 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,
e.g., *, +, {}, 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
Example 1:
char *cursor, *newcursor, *ptr;
...
Page 2 May 1989
REGCMP(3X) (Specialized Libraries) REGCMP(3X)
newcursor = regex((ptr = regcmp("^\n", (char *)0)), cursor);
free(ptr);
This example will match a leading new-line in the subject
string pointed at by cursor.
Example 2:
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);
This example will match through the string ``Testing3'' and
will return the address of the character after the last
matched character (the ``4''). The string ``Testing3'' will
be copied to the character array ret0.
Example 3:
#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.
These routines are kept in /lib/libPW.a.
SEE ALSO
regcmp(1), malloc(3C).
ed(1) in the User's Reference Manual.
BUGS
The user program may run out of memory if regcmp is called
iteratively without freeing the vectors no longer required.
Page 3 May 1989