add line to a file ONLY if it is not in file already

Question

I want to add the following line:

nohup java -jar /mnt/fusion/nfs/labStats/LabInfoAutoLog.jar > /dev/null &

to the end of the file /etc/rc.d/rc.local if it does not already exist.

How can I do that from linux command line? I assume grep or sed would work, but I am not familiar enough with either to get it to work. Right now I use echo, but that just keeps adding it over and over again.

score 15 · Accepted Answer · answered Jul 19 '13 at 14:07

15

Assuming you want it at the end of the file:

LINE="nohup java -jar /mnt/fusion/nfs/labStats/LabInfoAutoLog.jar > /dev/null &"
FILE=/etc/rc.d/rc.local
grep -q "$LINE" "$FILE" || echo "$LINE" >> "$FILE"

answered Jul 19 '13 at 14:07

ahilsend

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score 2 · Answer 2 · answered Jul 19 '13 at 14:05

2

one option is two steps:

grep -q "yourline" /path/file||sed -i '/..place../ a \the line' file

also possible to do with awk,

save all lines in array, during saving if the line was found, exit. otherwise, add the line in END{} block to the right place.

P.S. You didn't tell in the file, where to add that line.

answered Jul 19 '13 at 14:05

Kent

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+1 for a cleaner solution than mine. I think he just wants to append it. – Alberto Zaccagni Jul 19 '13 at 14:09
He says that currently uses `echo` so it will be the last one (dollar sign in `sed`). – Birei Jul 19 '13 at 14:09
@Birei when I answered it, there was no the `echo` part. :( but if he used echo, you are right. it should go to the last line. – Kent Jul 19 '13 at 14:22

add line to a file ONLY if it is not in file already

2 Answers2