Some interesting and useful Linux commands and BASH tricks.

Posted: October 25, 2016. At: 11:15 PM. This was 1 year ago. Post ID: 4760
Page permalink: http://securitronlinux.com/bejiitaswrath/some-interesting-and-useful-linux-commands-and-bash-tricks/

A useful awk implementation to count the number of entries in the /etc/passwd file.

[email protected]:~$ sudo awk -F: '{ print $1 }' /etc/passwd | wc -l
34

And the quintessential “Hello World” in Awk.

[email protected]:~$ awk 'BEGIN { printf "%s, %s\n", "Hello", "World!" }'
Hello, World!

This command will change your login shell if you wish to use an alternative.

[email protected]:~$ chsh -s /bin/tcsh
Password:

Shell quoting is a powerful feature of the BASH shell. This example shows how we are using a command within a command to generate output. Inception in BASH!

[email protected]:~$ echo "You have `ls | wc -l` files in `pwd`"
You have 17 files in /home/john

This example shows you may use the output of the ls command to provide a list of files to search for that contain a certain word or phrase.

john@deusexmachina:~/Desktop$ egrep '(Example)' `ls`
examples.desktop:Name=Examples
examples.desktop:Name[en_AU]=Examples
examples.desktop:Name[en_CA]=Examples
examples.desktop:Name[en_GB]=Examples
examples.desktop:Name[sco]=Examples
examples.desktop:Comment=Example content for Ubuntu
examples.desktop:Comment[en_AU]=Example content for Ubuntu
examples.desktop:Comment[en_CA]=Example content for Ubuntu
examples.desktop:Comment[en_GB]=Example content for Ubuntu
examples.desktop:Comment[sco]=Example content fur Ubuntu

Another way to print the current directory that you are in at the terminal or virtual console.

[email protected]:~$ echo ${PWD#*/}
home/john

And finally; this command will print out the last ten commands executed on your terminal.

[email protected]:~$ fc -l -10
140	 ls -hula | 's/Example/Content/'
141	 tail=${PWD##*/} 
142	 ls -hula | tail=${PWD##*/} 
143	 ls -hula | tail=${PWD#*/} 
144	 ls -hula | tail=${PWD##*/} 
145	 cd
146	 ls -hula | tail=${PWD##*/} 
147	 fc -l -10
148	 echo ${PWD##*/}
149	 echo ${PWD#*/}

if you want to edit the last command entered at the BASH shell; use this command: fc -e vi. This is good if it is a very long and complex command and you want an easier way to edit it.

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