Delete specific line number(s) from a text file using sed?
I want to delete one or more specific line numbers from a file. How would I do this using sed?
If you want to delete lines from 5 through 10 and line 12th:
sed -e '5,10d;12d' file
This will print the results to the screen. If you want to save the results to the same file:
sed -i.bak -e '5,10d;12d' file
This will store the unmodified file as file.bak
, and delete the given lines.
Note: Line numbers start at 1. The first line of the file is 1, not 0.
You can delete a particular single line with its line number by
sed -i '33d' file
This will delete the line on 33 line number and save the updated file.
and awk as well
awk 'NR!~/^(5|10|25)$/' file
$ cat foo
1
2
3
4
5
$ sed -e '2d;4d' foo
1
3
5
$
This is very often a symptom of an antipattern. The tool which produced the line numbers may well be replaced with one which deletes the lines right away. For example;
grep -nh error logfile | cut -d: -f1 | deletelines logfile
(where deletelines
is the utility you are imagining you need) is the same as
grep -v error logfile
Having said that, if you are in a situation where you genuinely need to perform this task, you can generate a simple sed
script from the file of line numbers. Humorously (but perhaps slightly confusingly) you can do this with sed
.
sed 's%$%d%' linenumbers
This accepts a file of line numbers, one per line, and produces, on standard output, the same line numbers with d
appended after each. This is a valid sed
script, which we can save to a file, or (on some platforms) pipe to another sed
instance:
sed 's%$%d%' linenumbers | sed -f - logfile
On some platforms, sed -f
does not understand the option argument -
to mean standard input, so you have to redirect the script to a temporary file, and clean it up when you are done, or maybe replace the lone dash with /dev/stdin
or /proc/$pid/fd/1
if your OS (or shell) has that.
As always, you can add -i
before the -f
option to have sed
edit the target file in place, instead of producing the result on standard output. On *BSDish platforms (including OSX) you need to supply an explicit argument to -i
as well; a common idiom is to supply an empty argument; -i ''
.