NAME
regcmp(), regex() — compile and execute regular expression
SYNOPSIS
#include <libgen.h>
char *regcmp(
const char *string1,
/* string2, */ ...
/*, (char *)0 */
);
char *regex(const char *re, const char *subject, ...);
extern char *__loc1;
Remarks
The ANSI C ", ...
" construct denotes a variable length argument list whose
optional [or required]
members are given in the associated comment
(/* */).
Features documented in this manual entry are obsolescent
and may be removed in a future
HP-UX
release.
Use of
regcomp(3C)
instead is recommended.
DESCRIPTION
regcmp()
compiles a regular expression
and returns a pointer to the compiled form.
malloc(3C)
is used to create space for the vector.
It is the user's responsibility to free unneeded space so allocated.
A
NULL
return from
regcmp()
indicates an incorrect argument.
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 largely 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.
- -
Used within brackets the hyphen signifies a character range.
For example,
[a-z]
is equivalent to
[abcd...xyz].
The
-
can represent 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 can be applied.
The value
m
is the minimum number and
u
is a maximum number, which must be no greater than 256.
The syntax
{m}
indicates the exact number of times the regular
expression can be applied.
The syntax
{m,}
is analogous to
{m,infinity}.
The plus
(+)
and asterisk
(*)
operations are equivalent to
{1,}
and
{0,}
respectively.
- (...)$n"
The value of the enclosed regular expression is returned.
The value is stored in the
(n+1)th
argument following the subject argument.
A maximum of ten enclosed regular expressions are allowed.
regex()
makes its assignments unconditionally.
- (...)
Parentheses are used for grouping.
An operator, such as
*,
+,
or
{ },
can work on a single character or a regular expression
enclosed in parentheses.
For example,
(a*(cb+)*)$0.
Since all of the above defined symbols are special characters,
they must be escaped to be used as themselves.
EXAMPLES
Match a leading new-line in the subject string to which the
cursor
points.
char *cursor, *newcursor, *ptr;
...
newcursor = regex((ptr = regcmp("^\n", 0)), cursor);
free(ptr);
Match through the string
Testing3
and return the address of the character
after the last matched character (cursor+11).
The string
Testing3
will be copied to the character array
ret0.
char ret0[9];
char *newcursor, *name;
...
name = regcmp("([A-Za-z][A-Za-z0-9_]{0,7})$0", 0);
newcursor = regex(name, "123Testing321", ret0);
WARNINGS
User programs that use
regcmp()
might run out of memory if
regcmp()
is called iteratively
without freeing vectors that are no longer required.
