How to use bash to replace a string

Question

I want to comment out this line in /etc/hosts:

127.0.0.1 test test

to become:

#127.0.0.1 test test

How to a one liner in bash command line to do this to find the line that just starts with 127? I am using Ubuntu 12.04.

Thanks

jbr · Accepted Answer · 2013-10-31T08:21:31.163

3

You can use sed(1):

sed -i '/^127/s/^/#/' /etc/hosts

-i means to do the substitution in place, so the substitution happens in /etc/hosts, not on stdout which is standard.

in '/^127/s/^/#/', '/^127/' means find a line starting with 127 (^ is the start of line anchor), the s/^/#/ substitute the start of that line with a #.

edited Oct 31 '13 at 08:21

answered Oct 31 '13 at 07:36

jbr

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score 2 · Answer 2 · edited Oct 31 '13 at 07:52

2

I think you can do this with the following command:

sed -i 's/127.0.0.1 test test/#127.0.0.1 test test/g' /etc/hosts

edited Oct 31 '13 at 07:52

Mark van Lent

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answered Oct 31 '13 at 07:37

Jente

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score 2 · Answer 3 · answered Oct 31 '13 at 07:47

2

Try using sed

sed -i.bak 's/^127/#&/' /etc/hosts

-i.bak - in place replace and create backup file with .bak

answered Oct 31 '13 at 07:47

jkshah

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How to use bash to replace a string

3 Answers3