Ttdfjt

We have the following line in a file on Linux:

discovery.uri=http://master.navada.com:8800

we want to add the word koko before master, so I just do:

sed –i 's/master/kokomaster/' file

which gives:

discovery.uri=http://kokomaster.navada.com:8800

but what we want is to add koko only if koko isn't already present before master.

For example, the next time that we run

sed –i 's/master/kokomaster/' file

the line will be:

discovery.uri=http://kokokokomaster.navada.com:8800

You can replace a bit more to avoid this problem:

sed -i sX/masterX/kokomasterX file

This replaces “/master”, so the next time you run it, nothing will be replaced, since “/kokomaster” doesn’t match.

sed -i '/kokomaster/!s/master/koko&/' file

First test whether the string kokomaster exists on the line, and if it doesn't, do the substitution. This is almost a literal translation of "but what we want is to add the koko word only if koko not exists before master word" into sed.

The & in the replacement part of the substitution will be replaced by the text matched by the pattern part (i.e. master).

After reading the comments (see below), you may want to use something more specific that would actually only modify the server name portion of the URI, and not any master string elsewhere, even if kokomaster occurred (or not) in the URI path:

sed -i 's,^(discovery.uri=http://)(master),1koko2,' file

You may even want to go as far as matching the exact and full line that you'd want to replace, just to avoid even hypothetical mistakes:

sed -i 's,^(discovery.uri=http://)(master.navada.com:8800)$,1koko2,' file

If the configuration file is written in JSON or some other well know format, you would not use sed at all, but jq or some other apropriate tool specifically written for handling files of that format.

Use

sed 's/(koko)*master/kokomaster/'

so master and any number of preceeding kokos get replaced.

If you're open to other tools:

perl -i -pe 's/(?<!koko)master/kokomaster/' file

The (?>!foo) is a negative lookbehind, so (?<!koko)master will only match master when not preceded by koko.

I have used below awk command to do the same

command

awk '$0 !~/kokomaster/gsub("master","kokomaster",$0)1' filename >file_tmp && mv file_tmp filename

output

discovery.uri=http://kokomaster.navada.com:8800
discovery.uri=http://kokomaster.navada.com:8800