Re: How to remove a specific line in a file

[Matthew Woehlke]

Eka1618 wrote:
> I am currently trying to figure out how to remove a specific line in a file.
> So far I've only been able to come up with Ideas such as removing blank
> lines, duplicate lines, or a number of line that are one right after
> another. I think that I should be using the commands grep, cat, and rm along
> with pipes to somhow make this work. 

Nope... you want to be using 'sed' (and this has nothing to do with 
bash, you should ask on a linux users' list). 'rm' removes files, not lines.

Your first try was actually "close" (you want to be using $(command) not 
'command', the latter does not execute programs but prevents expansions 
from occurring, i.e. treats the contents as a literal string) if you 
want to remove the first line, but using sed is much easier.

To remove line 5 from 'myfile' and write the result to 'mynewfile':
$ sed '5d' myfile > mynewfile

To remove all lines containing 'FOO' (same files):
$ sed '/FOO/d' myfile > mynewfile

To do both, and also delete lines 5-7:
$ sed -e '5d' -e '/FOO/d' -e '5,7d' myfile > mynewfile

Note that redirecting output to an input file is not recommended (you 
might end up truncating the file, for example). If you need to replace 
the file, it is best to write to a temporary file and use e.g. 'mv 
mynewfile myfile' when you are done.

It seems like there should be a way to delete the first match in pure 
sed, but I didn't figure it out in the few seconds testing I did. Anyway 
you can use 'grep -N' to get a line number to feed to sed. Also be sure 
to read the sed documentation, usually done with 'info sed'.

--
Matthew
"Will somebody get this walking carpet out of my way?!"
  -- Princess Leia Organa