Need to Replace Strings in Linux? Heres How to Do It in No Time

Okay, so, today I wanted to mess around with some strings in Linux, you know, just replacing some text within files. I remember there was this command, `sed`, that’s supposed to be good for this kind of thing. I had a bunch of configuration files where I needed to update a specific setting, and doing it manually would have been a real pain.

First, I had to dig up how `sed` actually works. Turns out, it’s a “stream editor,” which sounds kind of fancy, but basically, it reads files line by line and can perform edits on them. The basic command looked something like this:

`sed ‘s/old_text/new_text/g’ filename`

• `s` means substitute.
• `old_text` is what you want to find.
• `new_text` is what you want to replace it with.
• `g` means global, so it replaces all occurrences on a line, not just the first.
• `filename` is, well, the name of the file.

Seems simple enough, right?

First Try

So, I had this file, `*`, and I wanted to change all instances of “enabled” to “disabled”. I typed out:

`sed ‘s/enabled/disabled/g’ *`

I hit enter, and it just printed the whole file to the terminal, but with the changes. It didn’t actually modify the file itself. A bit of a rookie mistake, I guess. I did some quick searching and found out I needed the `-i` option to make it edit the file “in-place”.

Fixing it

So I updated my command to:

`sed -i ‘s/enabled/disabled/g’ *`

Ran it, and… nothing. No output. This time, that was a good sign. I opened `*`, and bam! All the “enabled” were now “disabled”. Success!

Multiple Files

Then I thought, what about multiple files? I had a whole directory of these things. I found out you can use wildcards, like `.txt` to apply it to all text files in the directory. I nervously typed out:

`sed -i ‘s/enabled/disabled/g’ .txt`

Fingers crossed, I ran it. Again, no output. I checked a few files, and it worked like a charm. All the files were updated.

Backup

But then I got a bit paranoid. What if I messed up? I found out that `sed -i` can create backups. You just add an extension after `-i`, like `*`. This creates a copy of the original file with the `.bak` extension before making changes. I wish I had known that before!

More Complex Stuff

Later, I had a case where I needed to replace text that had spaces in it. I thought I was screwed, but I just had to put the text in double quotes in the command. For example:

`sed -i “s/old text with spaces/new text with spaces/g” *`

It worked perfectly.

Conclusion

Overall, `sed` is pretty powerful once you get the hang of it. It saved me a lot of time and effort. Sure, I made some mistakes along the way, but that’s how you learn, right? Now I feel a bit more comfortable with the command line, and I have a new tool in my Linux toolkit. I will definitely use `sed` in the future to quickly process and replace text.