Regular expressions with Perl
From Bashlinux
How to search and replace a word or phrase
- All matches
perl -pi -e 's/old string/new string/g' /path/to/the/file
- This command line replaces all the instances of old string with new string that are found in `/path/to/the/file`. To replace only the first instance, remove the g at the end of the command.
- Conditional match
perl -pi -e 's/old string/new string/ if m/my unique string/' /path/to/the/file
- This command line search only for the lines that matches my unique string and then replaces old string with new string
- Search and replace using bash shell variables
sed -i -e s%old string%$BASH_VARIABLE% /path/to/the/file
- In order to get this done is convenient to use `sed` instead `perl` command.
- Always use `-i -e` instead `-ie`, if not you will end up with another file with the same name but with an `e` at the end of the file name.
How to remove/replace a whole line
- Conditional match
perl -pi -e '$_="" if m/my unique string/' /path/to/the/file
- This command line removes all the lines that matches my unique string
How to work with "sed" command
Attached is a file Media:sed1line.txt with a very useful list of sed commands called One-Liners for sed. Updated version is always available at http://sed.sourceforge.net/sed1line.txt