Using sed and grep/egrep to search and replace

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...

Another way to do this

find . -name *.xml -exec sed -i "s/4.6.0-SNAPSHOT/5.0.0-SNAPSHOT/" {} \;

Some help regarding the above command

The find will do the find for you on the current directory indicated by .

-name the name of the file in my case its pom.xml can give wild cards.

-exec execute

sed stream editor

-i ignore case

s is for substitute

/4.6.0.../ String to be searched

/5.0.0.../ String to be replaced

I couldn't get any of the commands on this page to work for me: the sed solution added a newline to the end of all the files it processed, and the perl solution was unable to accept enough arguments from find. I found this solution which works perfectly:

find . -type f -name '*.[hm]' -print0 
    | xargs -0 perl -pi -e 's/search_regex/replacement_string/g'

This will recurse down the current directory tree and replace search_regex with replacement_string in any files ending in .h or .m.

I have also used rpl for this purpose in the past.