To open a file as if you had double clicked in the finder, use this command. This will open myfile.jpg in the default jpg viewer.

open myfile.jpg


Many time you find yourself with a file that you want to open in a specific application. For this you can use the -a flag. This will work if the application is in a well known place. If the application is not in a well known place you can use the entire path to the application.

open -a Safari myfile.jpg
open -a /MyAdobeApps/Photoshop.app myfile.jpg

As shorthand for TextEdit, just use the -e file

open -e README.1st


If you have a program that generates output, you can pipe the results to open and have it show in TextEdit.

cal | open -f


And finally, you can also use this to open directories in Finder:

open .
open ~/Desktop

As an example, if I wanted to view a png file in hexadecimal, I could use hexdump from the command line:

hexdump myfile.png

0000000 89 50 4e 47 0d 0a 1a 0a 00 00 00 0d 49 48 44 52
0000010 00 00 00 0a 00 00 00 03 08 06 00 00 00 aa 3d 9e
0000020 75 00 00 00 09 70 48 59 73 00 00 0b 13 00 00 0b
0000030 13 01 00 9a 9c 18 00 00 00 04 67 41 4d 41 00 00

You could then whip out a handy hex to ascii chart, or you could use the command line tool “od”. This tool allows to specify what format you want the output in, for instance in ascii bytes. This makes it very clear that the first four bytes are the magic header for PNG files.

od -a HRidges.png

0000000   89   P   N   G  cr  nl sub  nl nul nul nul  cr   I   H   D   R
0000020  nul nul nul  nl nul nul nul etx  bs ack nul nul nul   ?   =  9e

You might find want to also have a hex editor so that you can edit the files as well. I tend to use 0xED.app. You can find it at Suavetech. An alternative to 0XED is HexFiend, which is also available in source code form.