help with sed

khill · 08-14-2008, 05:51 PM

hey, I need a bit of help using the command sed

what I want to do is include in a script a line which changes the umask inside of a user's .bashrc

from some searching, I think i'm 90% of the way there with:

Code:

grep umask .bashrc | sed 's/$1/umask 027/g' .bashrc

obviously the above doesn't work. So, how do I get sed to recognize the piped output of grep and include it in a replace?

khill · 08-14-2008, 05:56 PM

well geez, 5 more min of searching and I answered my own question

Code:

grep umask .bashrc | sed 's/{$1}/umask 027/g' .bashrc

colucix · 08-14-2008, 06:02 PM

Another way is

Code:

sed -i '/umask/s%.*%umask 027%' .bahsrc

or

Code:

sed -i 's%umask ...%umask 027%' .bashrc

these work only if the line containing the umask command is unique in .bashrc, otherwise you can get unwanted results. Also note that the -i option actually changes the content of the file. You may want to do a backup copy of your .bashrc before testing.

Edit: I tested your command and does not work for me...

colucix · 08-14-2008, 06:13 PM

Just a little add-on: if you want to be sure that user's .bashrc files contain a unique line with the umask command, you can consider something like this:

Code:

if [ $(grep -c umask .bashrc) -eq 1 ]
then
  sed -i '/umask/s%.*%umask 027%' .bahsrc
else
  echo ".bashrc contains more than one line with umask"
  echo "check it manually"
fi

khill · 08-15-2008, 11:35 AM

Well, my command doesn't work within a script, but it does work directly from the command line for me... odd that it wouldn't for you colucix. I'm using centOS if you can think of any relevant differences. Anyways, because I DO want to use this line in a script I was about to post and ask about another way to do it, but you've answered my question before I asked it colucix, thanks!