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Full Discussion: Regex learning.
Top Forums Shell Programming and Scripting Regex learning. Post 303044737 by RavinderSingh13 on Tuesday 3rd of March 2020 12:09:53 AM
Old 03-03-2020
Hello All,

Learnt an example of Lazy match in Regex in Perl, so thought to share here.
Let's say following is Input_file.

Code:
cat Input_file
abcdtest123^ DUMMYtestabcd12234 DUMMY bla blabla12231311313blabla bla.....,,,,,bla
test132131 ^ DUMMY blabla1213 121313_ 131y7351eg1eub wdfwfknfidh28e7ty;;;

Now we would like to have data between first occurrence of ^ to DUMMY , then we could use Lazy match like as follows:

Code:
perl -pe 's|(\^.*?DUMMY\s+)(.*)| new_text_here.... \2|'  Input_file

Output will be as follows for mentioned sample:
Code:
abcdtest123 new_text_here.... bla blabla12231311313blabla bla.....,,,,,bla
test132131  new_text_here.... blabla1213 121313_ 131y7351eg1eub wdfwfknfidh28e7ty;;;

Why is Lazy match Good here? Because .* is a GREEDY match and matches anything till last occurrence of any mentioned character etc but using Lazy match .*?DUMMY\s+ it matches very first occurrence of string DUMMY followed with space starting from ^

Tested and written this in PERL, thought/views/improvements are most welcome here.

Thanks,
R. Singh
This User Gave Thanks to RavinderSingh13 For This Post:
 

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RDUP-UP(1)							       rdup								RDUP-UP(1)

NAME
rdup-up - update a directory tree with a rdup archive SYNOPSIS
rdup-up [OPTION]... DIRECTORY DESCRIPTION
With rdup-up you can update an (possibly) existing directory structure with a rdup archive. The rdup archive has to be given to rdup-up's standard input. Username and uids rdup outputs both the username and uid, the receiving system (which may be a totally different system) checks if the username and uid match. If the username and uid don't match the (numeric) uid is used on the file. The same holds true for the groupname and gid. OPTIONS
-n Do a dry-run and do not create anything on disk. -t Create DIRECTORY (ala mkdir -p) if it does not exist. -s N Strip N path components from a pathname. If the resulting pathname is empty after this operation it is skipped. Be careful however with the following structure: /foo /foo/bar /foo/bar/bla.txt /foo/blork/bla.txt With rdup-up -s2 this will leave: <empty> <empty> /bla.txt /bla.txt And the last 'bla.txt' will overwrite the previous one, this will happen without warnings. -r PATH This option is related to the -s option, but works different. The string PATH is removed from (the beginning of) each pathname. With -r /home/backup the pathname /home/backup/bin/mycmd becomes /bin/mycmd. The same could be done with -s 2, but then you need to count the slashes. Note -s is always performed before -r. -v Be more verbose and echo the processed files to standard output. -vv Be even more verbose and echo processed file and the uid and gid information to standard output. -T Show a table of contents of the rdup stream received (ala tar -tf -). With -T the directory argument is optional. -T unsets any verbose (-v) options. -h A short help message. -V Show the version. EXIT CODE
rdup-up return a zero exit code on success, otherwise 1 is returned. AUTHOR
Written by Miek Gieben. REPORTING BUGS
Report bugs to <miek@miek.nl>. SEE ALSO
http:/www.miek.nl/projects/rdup/ is the main site of rdup. Also see rdup(1), rdup-tr(1) and rdup-backups(7). COPYRIGHT
Copyright (C) 2005-2010 Miek Gieben. This is free software. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. Licensed under the GPL version 3. See the file LICENSE in the source distribution of rdup. 1.1.11 13 Dec 2008 RDUP-UP(1)
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