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Full Discussion: Difference between space and [[:space:]] in regular expression
Top Forums UNIX for Dummies Questions & Answers Difference between space and [[:space:]] in regular expression Post 302837235 by bobbygsk on Thursday 25th of July 2013 11:35:51 AM
Old 07-25-2013
Difference between space and [[:space:]] in regular expression
May I know the difference between space in keyboard and [[:space:]] in regular expression

I entered the following
Code:
find . -type f -print | xargs grep -n 'dt=' | cut -d":" -f3 | sed 's/^ *dt=/dt=/g'
After "^" there is a space.
and the result is...
dt=`date +%Y%m%d%H%M%S`
        dt=`date +%Y%m%d`
dt=`date +%Y%m%d`
        dt=`date +%Y%m%d%H%M%S`
        dt=`date +%Y%m%d%H%M%S`
dt=`date +%Y%m%d%H%M%S`
        dt=`date +%Y%m%d%H%M%S`
        dt=`date +%Y%m%d%H%M%S`
        dt=`date +%Y%m%d%H%M%S`
dt=`date +%Y%m%d%H%M%S`
        dt=`date +%Y%m%d%H%M%S`
        dt=`date +%Y%m%d%H%M%S`

and when i used [[:space:]]

Code:
find . -type f -print | xargs grep -n 'dt=' | cut -d":" -f3 | sed 's/^[[:space:]]*dt=/dt=/g'
and the I got the expected result
dt=`date +%d%m%y_%H%M%S`
dt=`date +%d%m%y_%H%M%S`
dt=`date +%d%m%y_%H%M%S`
dt=`date +%d%m%y_%H%M%S`

---------- Post updated at 11:35 AM ---------- Previous update was at 11:31 AM ----------

By including space it did trimmed spaces for few of them.
 

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LEARN ABOUT SUSE

ausearch_add_regex

AUSEARCH_ADD_REGEX(3)						  Linux Audit API					     AUSEARCH_ADD_REGEX(3)

NAME

       ausearch_add_regex - use regular expression search rule

SYNOPSIS

       #include <auparse.h>

       int ausearch_add_regex(auparse_state_t *au, const char *expr);

DESCRIPTION

       ausearch_add_regex  adds  one  search condition based on a regular expression to the current audit search expression. The search conditions
       can then be used to scan logs, files, or buffers for something of interest. The regular	expression  follows  the  posix  extended  regular
       expression conventions, and is matched against the full record (without interpreting field values).

       If an existing search expression E is already defined, this function replaces it by (E && this_regexp).

RETURN VALUE

       Returns -1 if an error occurs; otherwise, 0 for success.

SEE ALSO

       ausearch_add_expression(3), ausearch_add_item(3), ausearch_clear(3), ausearch_next_event(3), regcomp(3).

AUTHOR

       Steve Grubb

Red Hat 							     Sept 2007						     AUSEARCH_ADD_REGEX(3)
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