[SOLVED] SED and Replacing Specific Line

bridrod · 08-24-2009, 12:09 PM

I have a file that contains the following line:

include = [ * ]

That above line shows up three times in the file.

The line I just want to replace is line 178 of that file.

How can I do that with SED? The problem seems to rely on using brackets and "asterisks" since they are apparently used as command parameters as well.

I tried different combinations unsuccessfully.

TIA,

-Rod

pwc101 · 08-24-2009, 12:11 PM

Code:

sed '178s/whatyouwanttogetridof/whatyouwanttoreplaceitwith/' input.txt > output.txt

bridrod · 08-24-2009, 12:19 PM

Quote:

Originally Posted by pwc101

Code:

sed '178s/whatyouwanttogetridof/whatyouwanttoreplaceitwith/' input.txt > output.txt

Thanks for the quick reply, but it doesn't seem to work:

sed '178s/include = [ * ]/include = [ emc* ]' /etc/evms.test > /etc/emvs.test2
sed: -e expression #1, char 39: unterminated `s' command

Any idea?

pwc101 · 08-24-2009, 12:33 PM

You're missing a final / and you need to escape (precede with a \) the special characters (spaces, brackets, asterisks etc.):

Code:

sed '178s/include\ =\ \[\ \*\ \]/include\ =\ \[\ emc\*\ \]/' /etc/evms.test > /etc/emvs.test2

pixellany · 08-24-2009, 01:15 PM

Really good SED tutorial here:
http://www.grymoire.com/Unix/Sed.html

You can also avoid some of the escapes by using sed -r (turns on extended regular expressions)

bridrod · 08-24-2009, 01:27 PM

Quote:

Originally Posted by pwc101

You're missing a final / and you need to escape (precede with a \) the special characters (spaces, brackets, asterisks etc.):

Code:

sed '178s/include\ =\ \[\ \*\ \]/include\ =\ \[\ emc\*\ \]/' /etc/evms.test > /etc/emvs.test2

Yep! Right on! Worked like a charm! Thanks. I did not know I had to use the "\" for the spaces and other characters.

Question... In my example I had a specific line to change, but how would I do the same job if I did not know the specific line, but knew it's the second occurrence in the file? Or maybe only knew it's actually between a range of lines (i.e.: 155-190 lines)?

Thanks for your input. It really saved me time here!

-Rod

bridrod · 08-24-2009, 01:28 PM

Quote:

Originally Posted by pixellany

Really good SED tutorial here:
http://www.grymoire.com/Unix/Sed.html

You can also avoid some of the escapes by using sed -r (turns on extended regular expressions)

Great link! Thanks!