regcmp(3x) DG/UX 4.30 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 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.
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 '$' character (ie.,
it is given no special meaning at all).
- Within brackets the minus means through. For
example, [a-z] is equivalent to [abcd...xyz]. The
- can appear as itself only if used as the first
or last character. For example, the character
class expression []-] matches the characters
] and -.
+ A regular expression followed by + means one or
more times. For example, [0-9]+ is equivalent to
[0-9][0-9]*.
{m} {m,} {m,u}
Integer values enclosed in {} indicate the number
of times the preceding regular expression is to be
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regcmp(3x) DG/UX 4.30 regcmp(3x)
applied. The value m is the minimum number and u
is a number, less than 256, which is the maximum.
If only m is present (e.g., {m}), it indicates the
exact number of times the regular expression is to
be applied. The value {m,} is analogous to
{m,infinity}. The plus (+) and star (*)
operations are equivalent to {1,} and {0,}
respectively.
( ... )$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).
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);
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regcmp(3x) DG/UX 4.30 regcmp(3x)
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
malloc(3C).
ed(1), regcmp(1) in the User's Reference for the DG/UX
System
WARNING
The user program may run out of memory if regcmp is called
iteratively without freeing the vectors no longer required.
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