Sort directories by number of files contained

Here is a one-liner which sorts all the directories under ‘/’ by the number of files contained:

find / -type d -exec sh -c 'ls -a1 "$1" | wc -l' \"{}\" {} \; -print | \
sed  '$!N;s/\n/ /' | sort -gr

I recently needed this on a linux server where the inode quota was exceeded. Through the one-liner I discovered where most of the inodes where consumed.

Cycle through the last argument of previous commands in Bash

In Bash, when I want to repeat the last argument of the previous command, I usually type !$. I just discovered that you can also use ALT+. to cycle through the last argument of previous commands.

ESC-g for glob expansion in bash

Just like <TAB> expands a filename given a prefix you can also expand a file name given the middle part of a file name.

Example:

$ ls
abc1def  abc2def  abc3def  abc4def  abc5def
$ ls *2*<ESC>g

Which will expand to:

$ ls abc2def

via a stackoverflow question

Bash extended pattern matching

If you don’t have extended pattern matching enabled you can enable it with shopt -s extglob

From the bash manual page:

If the extglob shell option is enabled using the shopt builtin, several
extended pattern matching operators are recognized. In the following
description, a pattern-list is a list of one or more patterns separated
by a |. Composite patterns may be formed using one or more of the fol‐
lowing sub-patterns:

?(pattern-list)
Matches zero or one occurrence of the given patterns
*(pattern-list)
Matches zero or more occurrences of the given patterns
+(pattern-list)
Matches one or more occurrences of the given patterns
@(pattern-list)
Matches one of the given patterns
!(pattern-list)
Matches anything except one of the given patterns

Example:

$ touch abc1d abc2d abcd abc11d abc3d
$ ls
abc11d abc1d abc2d abc3d abcd
$ ls abc?(1|2)d
abc1d abc2d abcd
$ ls abc*(1|2)d
abc11d abc1d abc2d abcd
$ ls abc+(1|2)d
abc11d abc1d abc2d
$ ls abc@(1|2)d
abc1d abc2d
$ ls abc!(1|2)d
abc11d abc3d abcd