Changing file extensions for all files in a directory on OS X

Question

I have a directory full of files with one extension (.txt in this case) that I want to automatically convert to another extension (.md).

Is there an easy terminal one-liner I can use to convert all of the files in this directory to a different file extension?

Or do I need to write a script with a regular expression?

Coady

Answer 1

You could use something like this:

for old in *.txt; do mv $old `basename $old .txt`.md; done

Make a copy first!

Vivienne

On Mavericks, this does not work for me, giving this output: usage: mv [-f | -i | -n] [-v] source target mv [-f | -i | -n] [-v] source ... directory – Keshiakesia

just tried it on Mavericks, and it works fine. This assumes you are using bash, the default shell. – Vivienne

Works fine on Mavericks, if you run into permission issues just insert sudo before the whole line, or enter a su. – Interment

This does not work for filenames with spaces in them without proper quoting. – Dinorahdinosaur

$old should be enclosed in double quotes here, lest much havoc could be wreaked. Edit: The whole `basename ...` too. – Intricate

With all the ways to get this wrong, I highly recommend the simple interactive Finder solution that Vicky posted instead. – Enteron

Any way of making it recursive? – Lynnette

@AlexandreCastro for old in **/*.txt; do mv $old "`dirname $old`/`basename $old .txt`.md"; done – Coumarin

Answer 2

Alternatively, you could install the ren (rename) utility

brew install ren

ren '*.txt' '#1.md'

If you want to rename files with prefix or suffix in file names

ren 'prefix_*.txt' 'prefix_#1.md'

Symbolism

This is the best suggestion for command-line renaming of files. Thanks! – Johanna

If you want to rename files with prefix or suffix in file names, you can use ren 'prefix_*.txt' 'prefix_#1.md' – Inelastic

@Scorn #16935627 – Symbolism

Answer 3

Terminal is not necessary for this... Just highlight all of the files you want to rename. Right click and select "Rename ## items" and just type ".txt" into to the "Find:" box and ".md" into the "Replace with:" box.

Simoniac

Yeah. This was great. In terminal: open . and then do this! Much easier. – Pe

Whoa!! Never knew about this! – Bloodthirsty

Nice find, but when renaming file extensions you typically have a lot of files to process. This method, on El Capitan, prompts you for each file asking if you really want to rename it. – Carlottacarlovingian

I've just tried on El Capitan, and it didn't prompt me for anything. Just renamed with no questions.... – Chickie

Wow, that was slick. I would recommend this over the terminal solution. – Raddled

Finder > Preferences > Advanced > Show warning before changing extensions. – Scorn

On Big Sur it will warn you but you can check the "apply to all files" box and it works. – Ivoryivorywhite

Answer 4

The preferred Unix way to do this (yes, OS X is based on Unix) is:

ls | sed 's/^\(.*\)\.txt$/mv "\1.txt" "\1.md"/' | sh

Why looping with for if ls by design loops through the whole list of filenames? You've got pipes, use them. You can create/modify not only output using commands, but also commands (right, that is commands created by a command, which is what Brian Kernighan, one of the inventors of Unix, liked most on Unix), so let's take a look what the ls and the sed produces by removing the pipe to sh:

$ ls | sed 's/^\(.*\)\.txt$/mv "\1.txt" "\1.md"/'
mv "firstfile.txt" "firstfile.md"
mv "second file.txt" "second file.md"
$

As you can see, it is not only an one-liner, but a complete script, which furthermore works by creating another script as output. So let's just feed the script produced by the one-liner script to sh, which is the script interpreter of OS X. Of course it works even for filenames with spaces in it.

BTW: Every time you type something in Terminal you create a script, even if it is only a single command with one word like ls or date etc. Everything running in a Unix shell is always a script/program, which is just some ASCII-based stream (in this case an instruction stream opposed to a data stream).

To see the actual commands being executed by sh, just add an -x option after sh, which turns on debugging output in the shell, so you will see every mv command being executed with the actual arguments passed by the sed editor script (yeah, another script inside the script :-) ).

However, if you like complexity, you can even use awk and if you like to install other programs to just do basic work, there is ren. I know even people who would prefer to write a 50-lines or so perl script for this simple every-day task.

Maybe it's easier in finder to rename files, but if connected remotely to a Mac (e.g. via ssh), using finder is not possible at all. That's why cmd line still is very useful.

Verlie

This works nicely - to do it recursively, change 'ls' to 'find . -name "*.txt"' – Pastern

Answer 5

You do not need a terminal for this one; here is a sample demonstration in MacOS Big Sur.

• Select all the files, right-click and select "rename..."

• Add the existing file extension in "Find" and the extension you want to replace with "Replace with".

And done!

Karlsruhe

Answer 6

Based on the selected and most accurate answer above, here's a bash function for reusability:

function change_all_extensions() {
    for old in *."$1"; do mv $old `basename $old ."$1"`."$2"; done
}

Usage:

$ change_all_extensions txt md

(I couldn't figure out how to get clean code formatting in a comment on that answer.)

Snowball

Answer 7

No need to write a script for it just hit this command

find ./ -name "*.txt" | xargs -I '{}' basename '{}' | sed 's/\.txt//' | xargs -I '{}' mv '{}.txt'  '{}.md'

Despotism

Answer 8

I had a similar problem where files were named .gifx.gif at the end and this worked in OS X to remove the last .gif:

for old in *.gifx.gif; do
    mv $(echo "$old") $(echo "$old" | sed 's/x.gif//');
done

Camion

This will modify a few more files than you intend if they have x?gif anywhere in the name (for example, maxsgift.gitx.git). This is best: sed s/\.gif$//'. – Buffum

Answer 9

    cd $YOUR_DIR
    ls *.txt > abc
    mkdir target // say i want to move it to another directory target in this case
    while read line
    do 
    file=$(echo $line |awk -F. '{ print $1 }')
    cp $line target/$file.md  // depends if u want  to move(mv) or copy(cp)
    done < abc

Alitaalitha

Answer 10

list=ls for file in $list do newf=echo $file|cut -f1 -d'.' echo "The newf is $newf" mv $file $newf.jpg done

Basque

Answer 11

If you're using the zsh shell

autoload -U zmv
zmv '(**/)(*).txt' '$1$2.md'

Anglian

Answer 12

Not sure if this was a mistake in the original accepted answer, but the original answer ADDS the .md file extension, it does not REPLACE the file extension. Also, the original answer would not work for filename with spaces in them. This worked for me:

for old in *.txt; do mv "$old" "`echo "${old%.*}"`.md"; done

Tower