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sed Case Insensitive Search Matching

Q. How do I perform a case-insensitive search using sed under UNIX / Linux? I’d like to match all combination of word – foo, FOO, FoO and so on while replacing or performing other operations.

A. GNU sed and other version does support a case-insensitive search using I flag after /regex/.

UNIX / Linux: sed Case Insensitive Search

To perform a case-insensitive search, enter:

cat file.txt | sed -e 's/find-word/replace-word/gI' 
cat file.txt | sed -e 's/find-word/replace-word/gI' > output.txt
sed 's/find-word/replace-word/gI' input.txt > output.txt

If you are using older sed version try,

sed 's/[wW][oO][rR][dD]/replace-word/g' input.txt > output.txt

It is easy to match first few characters, for example match both Linux and linux word:

sed 's/[Ll]inux/Unix/g' input.txt > output.txt
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{ 4 comments… add one }
  • Ni2 December 21, 2009, 7:48 am

    $ echo Cool | sed -n “/cool/Ip”

  • Ni2 December 21, 2009, 7:53 am

    sed version 4.1.5.

    Thanks for the tip. This is exactly what I was looking for.

  • skymaster September 26, 2013, 10:14 am

    sed -n -e ‘/patternmatch/Ip’ filetosearchin

  • arun January 1, 2017, 12:39 pm

    Printing with case sensitive is not working, as suggested by you. Could you check once again.

    [root@localhost ~]# yum install sed
    Loaded plugins: refresh-packagekit, rhnplugin
    Setting up Install Process
    Package sed-4.2.1-5.el6.x86_64 already installed and latest version
    Nothing to do

    [root@localhost ~]# sed -n ‘/oracle/’p passwd
    40 oracle:x:508:510::/home/oracle:/bin/bash
    41 Oracle:x:508:510::/home/oracle:/bin/bash

    [root@localhost ~]# sed -n ‘/oracle/’Ip passwd
    40 oracle:x:508:510::/home/oracle:/bin/bash
    41 Oracle:x:508:510::/home/oracle:/bin/bash

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