I am using egrep -R followed by a regular expression containing about 10 unions, so like:
.jpg | .png | .gif etc. This works well, now I would like to replace all strings found with .bmp
I was thinking of something like
egrep -lR "\.jpg|\.png|\.gif" . | sed "s/some_expression/.jpg/" file_it_came_form
so the issue here is how do I do a similar union regular expression in sed and how do I tell it to save the changes to the file that it got the input from.
Use this command:
egrep -lRZ "\.jpg|\.png|\.gif" . \
| xargs -0 -l sed -i -e 's/\.jpg\|\.gif\|\.png/.bmp/g'
egrep: find matching lines using extended regular expressions
-l: only list matching filenames
-R: search recursively through all given directories
-Z: use \0 as record separator
"\.jpg|\.png|\.gif": match one of the strings ".jpg", ".gif" or ".png"
.: start the search in the current directory
xargs: execute a command with the stdin as argument
-0: use \0 as record separator. This is important to match the -Z of egrep and to avoid being fooled by spaces and newlines in input filenames.
-l: use one line per command as parameter
sed: the stream editor
-i: replace the input file with the output without making a backup
-e: use the following argument as expression
's/\.jpg\|\.gif\|\.png/.bmp/g': replace all occurrences of the strings ".jpg", ".gif" or ".png" with ".bmp"
Honestly, much as I love sed for appropriate tasks, this is definitely a task for perl -- it's truly more powerful for this kind of one-liners, especially to "write it back to where it comes from" (perl's -i switch does it for you, and optionally also lets you keep the old version around e.g. with a .bak appended, just use -i.bak instead).
perl -i.bak -pe 's/\.jpg|\.png|\.gif/.jpg/
rather than intricate work in sed (if even possible there) or awk...
try something using a for loop
for i in `egrep -lR "YOURSEARCH" .` ; do echo $i; sed 's/f/k/' <$i >/tmp/`basename $i`; mv /tmp/`basename $i` $i; done
not pretty, but should do.