Linux Quick Tips

Things that I wish I’d known when I’d started

This segment is for the stupid little things that would have saved me an awful lot of time wasted had I known them when I first started playing with Linux…

Bash

bash#> CTRL-R

Search through your bash history

bash#> sudo !!

Repeat the last typed command as root

bash#> !55

Repeat the 55th typed command from your bash history (view your history by using the history command)

bash#> Alt-.

Add the argument to your previous command to the terminal (keep pressing it to cycle). (Submitted by vidda)

$ while [ 1 ] ; do command1 ; done

Run ‘command1′ on a loop.

$ while [ 1 ] ; do command1 ; command2 ; sleep 10 ; done

Run ‘command1′ and ‘command2′ on a 10 second loop.

$ mount | awk ‘{print $2}’

Print column 2 of a tabulated output (replace mount with the command that produces the output – this is called using a hammer to crack a nut, as awk is a whole other programming language), you can also set the delimiter by hand.

$ grep -i terms /file/to/search

Case insensitive grepping.

$ grep -v terms /file/to/search

Inverse grepping.

$ command | grep terms

Grep the output of a command.

$ command | wc -l

Count the lines of the command output.

$ echo $(($NUM+9))

Do maths between $(( and )), in this case adding 9 to the variable “NUM”.

$ ./configure && make && sudo make install

Does the latter command only if the prior command returned status 0 (ie. it worked).

$ echo $?

Show the status code of the last command to run (remember echo is a command).