How to use a shell variable inside sed when doing "d" command?

Question

In my bash, I wish to delete lines from 1 to ${number}, like this:

number=10
sed '1,${number}d' myfile

It failed with syntax error. I also tried "\${number}", '"$number"', neithers works

I changed to double quote, it works under command line, but not inside bash script file. How to make it work?

You need to put your variable outside of the quoted sed statement and so: sed '1,'${number}'d' myfile — Raman Sailopal, Jun 08 '17 at 10:07

score 2 · Answer 1 · answered Jun 08 '17 at 10:05

2

Enclose your sed expression in double quotes to interpolate the variable number:

sed "1,${number}d" file

answered Jun 08 '17 at 10:05

RomanPerekhrest

Thanks, it works under command line, but doesn't work inside a bash script. Seems bash script will do '1,$d' which will delete all. – Hind Forsum Jun 08 '17 at 10:53
`number` isn't defined in the script. – chepner Jun 08 '17 at 12:01
@HindForsum, post the crucial fragment of your bash script to your question so I could see your "sed" usage – RomanPerekhrest Jun 08 '17 at 12:05

score 2 · Answer 2 · answered Jun 08 '17 at 10:07

2

Please use double quotes instead of single quotes while running sed this way. Read here for Difference between single and double quotes

answered Jun 08 '17 at 10:07

asatsi

score 1 · Accepted Answer · answered Jun 08 '17 at 11:58

I changed to double quote, it works under command line, but not inside bash script file

Assuming your bash script is:

sed "1,${number}d" myfile

you should export number variable in bash prompt so that it can be visible in bash script when it is run:

export number=10

3 Answers3