CODEWITHSUNDEEP
linuxsedsh
peter
peter

Reputation: 4421

strip all from line starting after whitespace

I have a file with this content:

lines
lines
rootdev=UUID=967d8dc3-f595-4a6e-929e-cc89as5a1a2s               /               ext4    defaults,
lines

I am searching for one line command which should strip everything in the line rootdev after whitespace, so the final content should be like:

lines
lines
rootdev=UUID=967d8dc3-f595-4a6e-929e-cc89as5a1a2s
lines

Any idea how to do it with one line command? (so I do not need to open nano with this file and do it manually)

I tried with sed but it just replaces the word rootdev

sed -i 's/rootdev//g' file.txt

Upvotes: 1

Views: 120

Answers (2)

oguz ismail
oguz ismail

Reputation: 50805

First, search for a line beginning with rootdev=, and when you find it delete everything after the first whitespace until the end of line.

sed -i '/^rootdev=/ s/ .*$//' file

Using a capturing group to keep rootdev=... part in, and replacing the whole line with it is an option too.

sed -i 's/^\(rootdev=[^ ]*\).*$/\1/' file

Upvotes: 1

Inian
Inian

Reputation: 85885

Your attempt with sed can't work because it would just remove rootdev string with an empty string. What you need is a tool that matches a pattern and does an action on that whole line for which I think awk is more recommended than sed.

Using awk to match the line to strip off the spaces using gsub() should be sufficient,

awk '/^rootdev/{ gsub(/[[:space:]].*/,"",$0) }1' file

If you are using GNU awk with version greater than 4.1.0, you could use its in-place edit option to make the changes dynamically

gawk -i inplace '/^rootdev/{ gsub(/[[:space:]].*/,"",$0) }1' file

for earlier versions, use a temporary file

awk '/^rootdev/{ gsub(/[[:space:]].*/,"",$0) }1' file > temp && mv temp file

or use sponge from moreutils. If its not available in your system do get it on RHEL using yum install moreutils or with apt-get in Debian.

awk '/^rootdev/{ gsub(/[[:space:]].*/,"",$0) }1' file | sponge file

Upvotes: 2

Related Questions