Below are few different ways to print or extract a section of a file based on line numbers.
Lets try to extract lines between line number 27 and line number 99 of input file 'file.txt'
Using sed editor:
$ sed -n '27,99 p' file.txt > /tmp/file1
Which is same as:
$ sed '27,99 !d' file.txt > /tmp/file2
Awk alternative : you can make use of awk NR variable
$ awk 'NR >= 27 && NR <= 99' file.txt > /tmp/file3
Using Linux/UNIX 'head' and 'tail' command:
$ head -99 file.txt | tail -73 > /tmp/file4
Which is basically:
$ head -99 file.txt | tail -$(((99-27)+1)) > /tmp/file5
In vi editor, we can use the following command in ex mode (open the main file 'file.txt' in vi):
:27,99 w! /tmp/file6
i.e. Write lines between line number 27 and line number 99 of main file 'file.txt' to file '/tmp/file6'
Perl alternative would be:
$ perl -ne 'print if 27..99' file.txt > /tmp/file7
And the solution using python:
$ python
Python 2.5.2 (r252:60911, Jul 22 2009, 15:35:03)
[GCC 4.2.4 (Ubuntu 4.2.4-1ubuntu3)] on linux2
>>> fp = open("/tmp/file8","w")
>>> for i,line in enumerate(open("file.txt")):
... if i >= 26 and i < 99 :
... fp.write(line)
...
>>>
So the contents of all the output files produced (i.e /tmp/file[1-8]) will be the same (i.e. line number 27 to line number 99 of 'file.txt')
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5 comments:
python can also do one-liner for this one:
python -c "fp=open('/tmp/file8', 'w'); fp.write(''.join(open('file.txt', 'r').readlines()[25:99]))"
or if you want to use sheel redirection:
python -c "print(''.join(open('file.txt', 'r').readlines()[25:99]))" > /tmp/file8
@ps axu : thanks for your comment. Its useful.
Hi, first of all, thanks a lot, I'm finding so many things I didn't know how to do.
Just one question on this regard.
In the example:
sed -n '27,99 p' file > anotherfile
what would be the sintaxis to use variables instead of numbers?
I've tried a lot of ways, but nothing seems to work.
Thanks again, and good luck.
@Seifer, thanks for your question. To use variable use double quotes instead of single quotes, something like this:
m=27; n=99; sed -n "$m,$n p" file
A related post here:
http://unstableme.blogspot.com/2008/03/accessing-external-variable-in-awk-and.html
Keep in touch. Thanks
I am trying to recursively extract line 14 using sed from all conf files in a directory but I am not sure what the correct command is.
I've tried this but it only prints line 14 from the first file:
sed -n 14p *.conf
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