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Full Discussion: Need help with regex groups
Top Forums Shell Programming and Scripting Need help with regex groups Post 302532945 by sam_roy on Wednesday 22nd of June 2011 12:46:33 PM
Old 06-22-2011
Need help with regex groups

I have a requirement - replace specified positions in a string with a character. I found perl regex useful for this approach. however, I am facing the following issue.

The target file 'temp' contains -
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

The goal is to convert position 3 and 4 with '55'. Following is the script-

Code:
#!/bin/ksh

position=2
value='55'

nxtpos=4
len_val=2
#head -2 test| tail -1 > temp
x=`perl -pi -e "s/(.{$position})(.*)/\1$value\2/" temp`
echo $x

however on running it, it interprets the \1$value as \155, and replaces nothing.

Could you please suggest what can be done?

Last edited by Franklin52; 06-23-2011 at 03:48 AM.. Reason: Please use code tags, thank you
 

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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(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. ATTRIBUTES
Multithreading (see pthreads(7)) The re_comp() and re_exec() functions are not thread-safe. 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 3.53 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
2013-06-21 RE_COMP(3)
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