How to change file extensions command line MacOS


Linux has a handy rename command which is great for easily renaming file extensions within a directory.

> rename .htm .html *.htm

MacOS however has no such command.

Fortunately, Ben Han documented a nice work around by creating a simple script.
(Click here for a reminder on how to create MacOS scripts)

for f in *.$1
  mv $f ${f%$1}$2

It uses the mv command and loops through your directory doing the move based on whatever parameters you pass in.

For example to change all my pngs to jpgs all I have to do now is navigate to the target directory and type:

> png jpg

And voila! All my pngs are now jpgs.

Thanks again Ben for this great tip.

How to zip all files of certain file extension (UNIX, MacOS)

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As part of trying to do more things from the command line here’s a handy command for zipping files by type on MacOS from the command line.

find . -name "*.jpg" -print | zip source -@

You can find this an other commands from the zip man page.

How to create a UNIX bash script on a mac


The ability to create and make your own custom bash scripts is on of the biggest advantages to working off a unix based operating system (like the mac).

You can take just about any mundane, or complicated task, and easily automated it by learning how to create your own bash scripts.

In this post I am going to show you how to create a bash script called:

(which recursively search all files for text containing xxx (very handy)) and call it from anywhere on your computer.

Setup your environment

Go to your home directory:

$ cd ~

and make a directory called scripts (this is where you will store your scripts):

$ mkdir scripts

Then if you don’t have one already, create a .bash_profile file (in your root directory) and add the following line:

export PATH=$PATH:~/scripts

This puts the directory you just created into the unix $PATH variable which lets you call your scripts from anywhere on your machine.

To register this new path you may need to go:

$ source .bash_profile

You can then check your new path by typing:

$ echo $PATH

If all is well you should see your new directory in the output.

OK. We are now ready to create your script.

Create your script

To create your script go back to that scripts directory your just created and using your favorite text editor create a file called ‘’

echo "Searching for text:" $1
find . -type f -exec grep -il $1 {} \;

And give yourself permission to execute it using the following command:

$ chmod 711

That’s it! At this point you are basically done.

You should now be able to run this script from anywhere on your box.

To test it out, navigate to some directory containing a lot of files and text and search for something.

Here is the output I get when I search my rails app for ‘README’

Searching for text: README

Add your aliases

You can also add aliases to your .bash_profile to help make your life easier.

alias dev='cd /Users/jr/Documents/dev/rails'

Now I can type ‘dev’ and instant be taken to my development directory.

For more information on bash and scripting click here.

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