Question

A bug in some code I wrote resulted in some files being formatted incorrectly. If it were only one file, I could write

cat filename | sed 's/bad/good/g' >filename2
mv filename2 filename

and fix it. I have several hundred files, however, and I would like to make the same transformation on all of them.

Is there some way to apply the same transformation to a large number of files with sed, keeping the filenames the same?

Is sed even the right tool for this job? If not, what should I use?

Answer 1

Use the -i (in-place) option on modern versions of sed.

sed -i 's/bad/good/g' file*pattern

or, with find

find . -type f -name 'file*pattern' -print0 | xargs -0 sed -i 's/bad/good/g'

If you’re concerned about something going awry, you can supply a suffix as an argument to -i, and a backup copy of each file will be saved with that suffix before the transformation is applied:

sed -i.bak 's/bad/good/g' filename
diff filename.bak filename

If your version of sed doesn’t support the -i option, you can always use perl, which is where sed got the idea (only fair, since much of perl’s command-line syntax comes from sed):

perl -pi.bak -e 's/bad/good/g' filenames