Perl regex search and replace in many files

Perl regex search/replace FAQ: How do I replace every TAB character in a file with a comma? (More generally, how do I search for a Perl regex pattern, and replace it with a different string?)

Perl regex search and replace

Replacing each TAB character in a file with a comma character can be accomplished several different ways with Perl. The key in any approach is to perform a Perl regex search and replace operation.

(Note: Please make a backup of your file(s) before continuing.)

My favorite way to solve this problem is to run a Perl search and replace command from the Linux command line. I like to do this using a command which edits the file in place, so I don't have to do that pesky process of making the changes, saving them to a different file, and then having to rename that new file to the old filename.

So, to run a Perl search and replace command from the command line, and edit the file in place, use this command:

perl -pi.bak -e 's/\t/,/g' myfile.txt

This command makes the search-and-replace changes to the file 'myfile.txt', and in this case I also make a backup file named myfile.txt.bak (in case we make an error). The new version of myfile.txt contains the changes you just made -- all the TAB characters have been converted to commas.

Perl command line options used

The command line options I used in this Perl example are:

-p
    Assumes an input loop around your script.
      
-i EXT
    Files processed by the <> construct are to 
    be edited in-place.
      
-e COMMANDS
    May be used to enter one line of a script 
    (or, in this case, a one-line script). 

Perl regex search and replace - More general situation

Of course the more general question is "How do I replace every instance of Character A with Character B in a file with Perl?" Just replace the TAB and comma in the Perl code/command I shared above, and you should be in good shape.

Comments

I just ran into a situation where I needed to convert a tab-delimited spreadsheet file into a comma-delimited file I could import into a database, and used this exact command.

Note that this is an improvement over the Unix sed command, where you can't edit a file in-place. With sed, you have to open the original file, read it's contents, write the changes to a new file, move the original file to a backup name, and then move the new file to the original file name. This is easier done than said, but requires the use of a shell wrapper. Using Perl to edit the file in-place is certainly much easier.

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