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Top Forums Shell Programming and Scripting Perl newbie - regex replace all groups issue Post 302585382 by samask on Wednesday 28th of December 2011 09:03:47 AM
Old 12-28-2011
regex replace all groups issue

Hello,

Although I have found similar questions, I could not find
advice that could help with my problem. The issue:

I am trying to replace all occurrences of a regex, but
I cannot make the regex groups work together.

This is a simple input test file:
Code:
The Vedanta Philosophy
~~~~~~~~~~~~~~~

Body text

This is what the output should be:
Code:
## The Vedanta Philosophy

Body text

This is my code:
Code:
#!/usr/bin/perl -w

use strict;

while (<>) {
    s/(^.*)\n(^~+)/## $1/igm;
    print;
}


sub usage {
    (my $progname = $0) =~ s/.*[\\\/]//;
    die "Usage: $progname [<file>...]\n";
}

The two groups
Code:
(^.*)

and
Code:
(^~+)

match the test file independently, but when
I put them together in the s///igm line, they do not work at all.

I read the perl regex introduction and tutorial, and
searched for hints where I am making a mistake, with no avail.

Smilie

Thank you for any help or indication on how to solve this problem.

Last edited by samask; 12-28-2011 at 02:03 PM.. Reason: minor correction
 

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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(const char *regex); int re_exec(const 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. ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7). +---------------------+---------------+-----------+ |Interface | Attribute | Value | +---------------------+---------------+-----------+ |re_comp(), re_exec() | Thread safety | MT-Unsafe | +---------------------+---------------+-----------+ 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 4.15 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/. GNU
2017-09-15 RE_COMP(3)
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