REGCMP(3X) DOMAIN/IX Reference Manual (SYS5) REGCMP(3X)
NAME
regcmp, regex - compile and execute regular expression
USAGE
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 and returns a pointer
to the compiled form. Malloc(3C) creates space for the vec-
tor, though it does not automatically free unneeded space
that was allocated. A NULL return from regcmp indicates an
incorrect argument. Regcmp(1) was written to preclude the
need to use the 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, a pointer to the next
unmatched character on success. A global character pointer
loc1 points to where the match began. Regcmp and regex
derive from the editor, ed(1); however, the syntax and
semantics have been changed slightly.
SYMBOLS
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.
- Within brackets, the minus means ``through.'' For
example, [a-z] is equivalent to [abcd...xyz]. The
- can appear as itself only if it is used as the
first or last character. For example, the charac-
ter 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
Printed 5/10/85 REGCMP-1
REGCMP(3X) DOMAIN/IX Reference Manual (SYS5) REGCMP(3X)
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 (*) opera-
tions are equivalent to {1,} and {0,} respec-
tively.
( ... )$n The value of the enclosed regular expression is to
be returned. The value will be stored in the
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 to be treated as literals.
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 pointed at by cursor.
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 will match through the string ``Testing3'' and
will return the address of the character after the last
matched character (cursor+11). 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.
REGCMP-2 Printed 5/10/85
REGCMP(3X) DOMAIN/IX Reference Manual (SYS5) REGCMP(3X)
This routine is kept in the directroy ``/lib/libPW.a.''
NOTES
The user program may run out of memory if regcmp is called
iteratively, without first freeing the vectors that are no
longer required. The following user-supplied replacement
for malloc(3C) reuses the same vector saving time and space:
/* user's program */
...
char *
malloc(n)
unsigned n;
{
static char rebuf[512];
return (n <= sizeof rebuf) ? rebuf : NULL;
}
RELATED INFORMATION
ed(1), regcmp(1) malloc(3C)
Printed 5/10/85 REGCMP-3