09-05-2011
Of course it's slow, what you're doing is akin to trying to repairing a watch using a hammer: it's possible, but frustrating. In this case, the regex as you're applying it has to scan each line completely, checking each character on each line, checking for a match.
So the first question is: is it really a regex, or is it a fixed string?
And the second: can the regex be anchored in some way? Eg, start of the line, or the only word on the line, or something else to minimize the search cost?
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LEARN ABOUT LINUX
re_exec
RE_COMP(3) Linux Programmer's Manual RE_COMP(3)
NAME
re_comp, re_exec - BSD regex functions
SYNOPSIS
#define _REGEX_RE_COMP
#include <sys/types.h>
#include <regex.h>
char *re_comp(char *regex);
int re_exec(char *string);
DESCRIPTION
re_comp() is used to compile the null-terminated regular expression pointed to by regex. The compiled pattern occupies a static area, the
pattern buffer, which is overwritten by subsequent use of re_comp(). If regex is NULL, no operation is performed and the pattern buffer's
contents are not altered.
re_exec() is used to assess whether the null-terminated string pointed to by string matches the previously compiled regex.
RETURN VALUE
re_comp() returns NULL on successful compilation of regex otherwise it returns a pointer to an appropriate error message.
re_exec() returns 1 for a successful match, zero for failure.
CONFORMING TO
4.3BSD.
NOTES
These functions are obsolete; the functions documented in regcomp(3) should be used instead.
SEE ALSO
regcomp(3), regex(7), GNU regex manual
COLOPHON
This page is part of release 3.27 of the Linux man-pages project. A description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
GNU
1995-07-14 RE_COMP(3)