Frequency list bash function

In addition to command aliases (see an earlier post), you can add your own functions to the bash shell. Here is a simple but useful command line sequence:

function freq() {
    sort $* | uniq -c | sort -rn;
}

Put it in ~/.bashrc and you will have a freq command for creating frequency lists:

freq <FILES>

will sort and count all identical lines of the input file(s), and present them in descending frequency. Useful in many situations, not the least for checking that files that are supposed to only contain unique lines actually do so.

(I'm not too sure about bash function syntax, but the function above seems to do its work.)

If you're not familiar with the different commands of the pipeline above, there is plenty to read (e.g., egrep for linguists).

Favourite bash command line aliases

My favourite bash aliases currently are

alias hist='history|egrep'

and

alias ös='ls'

The second one for the reason that 'ö' sits next to 'l' on my Swedish keyboard, and when I intended to type 'ls' I type 'ös' more often than not. The one I use the most, however, is alias more='m' (I also have the classic more='mroe' and more='moer' to catch some frequent typos).

The first one, hist, makes it possible to use regular expressions to search the history of earlier shell commands. This is useful when you cannot remember some tricky command line sequence, or are too lazy to type some long command that you know you issued the other day.

For instance

hist 'java|ruby'

will print any previous command (in bash's history) containing any of the two strings.

(Well, I think you can accomplish the same thing using the original history command, but to paraphrase Morrissey, now my head is full, and my brain doesn't have room for more cryptic command line arguments.)

You can put your bash aliases in ~/.bashrc.

(Thanks to Chris for spotting a (now corrected) mistake in the first example. See the comment below.)

Update: Hey, checkout the comment by Anonymous below: Ctrl-r seems useful for searching the Bash history!