CODEWITHSUNDEEP
bashsed
William
William

Reputation: 59

Bash - Deleting a line from file using sed

Probably a pretty straight forward one but I'm fairly new to bash I'm trying to delete a line from a .txt file that contains a specific string. The string is specified as a variable "$logline"

My code for sed is currently: 

logline="example2"
sed -i "/$logline/d" > /root/file.txt

The contents of the /root/file.txt file is...

/root/Dir/example.txt
/root/Dir2/example2.txt
/root/Dir/example3.html
...

I expect just the line /root/Dir2/example2.txt to be deleted.

However when I run this the entire txt file is getting wiped, and I get the error message sed: no input files.

Any idea what I'm missing here?

Thanks

Upvotes: 1

Views: 175

Answers (2)

Toby Speight
Toby Speight

Reputation: 30704

If your variable $logline contains exact text to be matched, sed is probably the wrong program to be using. Pattern addresses are regular expressions, and you'll need to escape any of the metacharacters understood in basic REs, including \, * and ..

For removing a fixed string, you'll probably find it easier to use grep -Fv; something like

grep -Fv -- "$logline" <"$file" >"$file.new"; mv "$file.new" "$file"

If you really must use sed, you should choose whether you're editing in-place with -i or using standard output - you don't get both. So either

  • sed -i "/$logline/d" "$file"

  • sed "/$logline/d" "$file" >"$file.new" && mv "$file.new" "$file"

Upvotes: 2

that other guy
that other guy

Reputation: 123410

sed -i has no output, so when you redirect to a file it will just be truncated.

Instead, give the filename to sed directly without redirecting:

sed -i "/$logline/d" /root/file.txt

Upvotes: 2

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