I’ve been reading some cool stuff about Bash lately. Hopefully, they are useful to you, too. This post really combines things from this page and this page.

I run the following command:

$ l sizer svg2png.py mypdf.pdf
-rw-r--r-- 1 hostetlerm mkgroup-l-d 219975 Mar  8 16:38 mypdf.pdf
-rwxr-xr-x 1 hostetlerm mkgroup-l-d   2927 May 18 09:27 sizer
-rwx------ 1 hostetlerm mkgroup-l-d    381 May 18 09:27 svg2png.py

Huh? What’s sizer? I want to run file on it to figure it out. Since it’s the first argument, I can just do this:

$ file !^

And it puts the first argument in:

file sizer
sizer: ASCII English text

Why !^? It sorta makes sense — Bash uses ! to control and ^ is the beginning of the line in regular expressions.

To get the last argument, you would use !$, which makes sense for the same reasons.

But I will probably never remember the ^ and $, but luckily I can do numbers as well:

$ file !:1
file sizer
sizer: ASCII English text

So !:1 is the first argument. It follows that !:2 is the second, etc.

If you just want all the arguments, just use !*:

$ l sizer svg2png.py mypdf.pdf
-rw-r--r-- 1 hostetlerm mkgroup-l-d 219975 Mar  8 16:38 mypdf.pdf
-rwxr-xr-x 1 hostetlerm mkgroup-l-d   2927 May 18 09:27 sizer
-rwx------ 1 hostetlerm mkgroup-l-d    381 May 18 09:27 svg2png.py

$ file !*
file sizer svg2png.py mypdf.pdf
sizer:      ASCII English text
svg2png.py: a python\015 script text executable
mypdf.pdf:  PDF document, version 1.3

Now if this isn’t cool enough, I put this in my $HOME/.inputrc:

$if Bash
  Space: magic-space
$endif

$HOME/.inputrc your configuration file for the Readline library, which Bash and scads of other Unix tools uses. Read more about inputrc — there is a ton of hacking potential there. If you don’t want to log out and log back in, you can hit ^C^R to re-read the inputrc file.

What does this magic-space do? Well, it’s magic. Now I can type this, leaving my cursor at the very end:

$ file !*_

And when I hit <space>, !* is replaced with the proper values!

file sizer svg2png.py mypdf.pdf _

See? I told you it was magic!

Thus ends our lesson for today. Calling back previous arguments with simple commands is simply ingenious and I have to admit, the magic space surprised a little. But it’s all very, very cool.