CODEWITHSUNDEEP
sed
dhruvabedre
dhruvabedre

Reputation: 55

Replace a matching string from the end of line using sed

I have a file content like,

/var/lib/mlocate
/var/lib/dpkg/info/mlocate.conffiles
/var/lib/dpkg/info/mlocate.list
/var/lib/dpkg/info/mlocate.md5sums
/var/lib/dpkg/info/mlocate.postinst
/var/lib/dpkg/info/mlocate.postrm
/var/lib/dpkg/info/mlocate.prerm

In the above file content I want to replace the last slash(/) on every line with space using sed like below

/var/lib mlocate
/var/lib/dpkg/info mlocate.conffiles
/var/lib/dpkg/info mlocate.list
/var/lib/dpkg/info mlocate.md5sums
/var/lib/dpkg/info mlocate.postinst
/var/lib/dpkg/info mlocate.postrm
/var/lib/dpkg/info mlocate.prerm

Please help me in this.

Upvotes: 0

Views: 159

Answers (2)

mklement0
mklement0

Reputation: 440657

sed 's|\(.*\)/|\1 |' file

  • sed's regexes are greedy by default, so .*/ matches everything up to the last / instance.

  • sed uses BREs (basic regular expressions) by default, in which, perhaps surprisingly, ( and ) must be \-escaped in order to enclose a capture group (capture the enclosed sub-expression separately).

    • GNU (Linux) Sed and BSD/macOS Sed support nonstandard option -E to enable EREs (extended regular expressions), in which case you don't need the escaping of parentheses:
      sed -E 's|(.*)/|\1 |' file # or -r with GNU Sed / non-macOS BSD Sed

  • Note how regex delimiter | was chosen instead of the customary /; using | allows unescaped use of / as a literal to match.

  • In the replacement part, \1 refers to what the 1st (and only) capture group (\(...\)) matched, which is everything up to, but not including, the last /. By following \1 with a literal space you get the desired result.

Upvotes: 1

P....
P....

Reputation: 18411

awk version: NO reason to do the task with this. But it works :)

awk 'BEGIN{FS=OFS="/"} {$(NF-1)=$(NF-1) " " $NF; NF--} 1' inputfle
/var/lib mlocate
/var/lib/dpkg/info mlocate.conffiles
/var/lib/dpkg/info mlocate.list
/var/lib/dpkg/info mlocate.md5sums
/var/lib/dpkg/info mlocate.postinst
/var/lib/dpkg/info mlocate.postrm
/var/lib/dpkg/info mlocate.prerm

Upvotes: 0

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