CODEWITHSUNDEEP
bashvariablessed
cBoLsmUiEc
cBoLsmUiEc

Reputation: 53

Trimming a textfile

i want to trim a textfile and delete all lines from line n to the end of the file. I tried to use sed for that. The sed command for n=26 should look like that:

sed -i '26,$d' /path/to/textfile

So in my textfile i don't know n beforehand, but i know that there is a unique text in that line. So i tried it that way:

myvar=`grep -n 'unique text' /path/to/textfile | awk -F":" '{print $1 }'`
sed -i "${myvar}"',$d' /path/to/textfile

That works and deletes all wanted lines but it throws the error message:

sed: -e expression # 1, character 1: unknown command: »,«

So i tried changing my command to:

myvar=`grep -n 'unique text' /path/to/textfile | awk -F":" '{print $1 }'`
sed -i "${myvar},$d" /path/to/textfile

With that i get the same error message but it doesn't delete the lines. I tried some variations with ' and " and how to put the variable in there, but it never works as wanted. Does someone knows what i do wrong?

I would appreciate other methods for trimming the textfile as long as i can do it in a bash script.

Upvotes: 0

Views: 48

Answers (1)

chepner
chepner

Reputation: 531055

You can replace the fixed line number with a regular expression matching the line to start at.

sed -i '/unique text/,$d' /path/to/textfile

You can also use ed to edit the file, rather than rely on a non-standard sed extension.

printf '/unique text/,$d\nwq\n' | ed /path/to/textfile

Upvotes: 2

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