I have a lot of text file with specific tag called "Comment", example I have a file called 3dchess.sh,
I need change the tag:
Comment=3D chess for X11 to
Comment='<span size="xx-large">3D chess for X11</b>' The script is:
#!/bin/sh Package=3dchess Popcon=48 Section=universe Comment=3D chess for X11 Exec=3Dc I have tried this but it doesn't work in my case:
sed -i ':Comment=:s:Comment=:Comment='<span size="xx-large">:g;/Comment=/s/$/</b>'/' $HOME/3dchess.sh Personally, I like the -r option of sed that allows extended regular expressions so parentheses don't need to be escaped:
sed -r "s#(Comment=)(.*)#\1'<span size=\"xx-large\">\2</b>'#" 3dchess.sh Note that since you want to use ' in the substitution, you cannot use sed 's///' but need to use sed "s///" instead. Also, since you need to have / as part of the pattern, you can't use that as a delimiter so you need to choose another character. I picked # but you can use anything you like. As Graeme said, once you're sure this works OK, add the -i switch to make it edit the file in place.
sed 's:^Comment=\(.*$\):Comment='\''<span size="xx-large">\1</b>'\': \ $HOME/3dchess.sh Add -i when you are sure you have what you want.
s:x:y: - This is the overall replacement pattern, basically replace x with y. Obviously we have a lot more between the colons above! Usually : is / but sed takes whatever comes after the s and using / here would mean you need to escape it in the pattern.
^Comment= - regex match Comment= at the start of a line ( ^ ). Good practice since it is possible (though unlikely) to get this elsewhere, which would cause problems.
\(.*$\) - match anything ( .* ) up to the end of the line ( $ ). Surrounding with \( \) creates a back reference for use later.
'\'' - close the '' quotes, put a literal ' and reopen quotes. Alternative method to @terdon's.
Comment=<span size="xx-large">\1</b> - replacement string, \1 is the backreference from before.
'\': - close quotes, put a literal ' then the final colon.
echo 'Comment=3D chess for X11' | sed 's:^Comment=\(.*$\):'\''Comment=<span size="xx-large">\1</b>'\':. What shell are you using?