Lindesk

A few tips and tricks on the terminal to make you more efficient when using it. If you know of any other tips, add it in the comments section.

1. ls Without ls

When you are trying to cd into a deep folder, you might not know the correct folder name some levels deep. You might have to do something like…

$ cd ~/Scripts/Perl
$ ls
bin	SedGUI       ToSee	Cronjobs  Maintenance
$ cd Maintenance

There is an easier way – go to the wanted folder

$ cd ~/Scripts/Perl

Now, without pressing enter, double tap the TAB key. You will get a list of files. And the command prompt waiting to be filled…

$ cd ~/Scripts/Perl/[TAB TAB]
bin	SedGUI       ToSee	Cronjobs  Maintenance
$ cd ~/Scripts/Perl/_

You can also use double-TAB to auto-complete commands.

2. Searching the history with Ctrl+R

If you have to use a command you have already used before, press CTRL+R and then type a few characters of the command. The latest command with those characters will be shown – if that is the command you want to execute, press enter and it will be executed. If not, just press CTRL+R again and it will show the next command.

You have no idea how useful this tip is if you haven’t been using it. I use this all the time.

For more details, read this article.

3. Open Terminal using a Shortcut

If you are a GUI user, chances are you prefer using a Terminal emulator(like gnome-terminal or konsole) instead of going into the Terminal mode by pressing CTRL+ALT+F1. If so, assign a shortcut to those emulator apps. I prefer using the shortcut ‘Ctrl+Alt+A’ to do this.

Gnome

If you are in gnome, there is a very easy way to do this…

• Go to System > Preferences > Keyboard Shortcuts
• Find ‘Run a Terminal’ – assign the shortcut ‘Ctrl+Alt+A’

KDE

• Right Click on the K-Menu > Menu Editor
• Find your terminal application in the list(usually System > Terminal Applications > Terminal)
• Select the ‘Current Shortcut Key’ option and set it to ‘Ctrl+Alt+A’

You can also do this by opening the KHotKeys application.

4. Bash Keyboard Shortcuts

Learn the bash keyboard shortcuts – these are the ones I use the most…

CTRL+R

Search the history. We already talked about this.

CTRL+L

Clears the screen. Use this instead of the clear command.

CTRL+D

Use this instead of the exit command.

CTRL+C

Kill whatever is running

CTRL+Z

Puts whatever is running into a suspended background process. Use fg to restore it.

5. Find Command using apropos

Find the command you want using the apropos command. Just type in a description of the command as the first argument. For example, lets say you want to find the command to list the directory contents. Use the command…

$ apropos "directory contents"
dir                  (1)  - list directory contents
ls                   (1)  - list directory contents
ls                   (1p)  - list directory contents
ntfsls               (8)  - list directory contents on an NTFS filesystem
vdir                 (1)  - list directory contents

The only problem is that I can never spell ‘apropos’ – so I keep this in my .bashrc file…

alias apox='apropos'

6. Learn New Commands

There are a few sites that publish cool commands on a daily/semi-daily basics – subscribe to those and learn new commands…

There are some settings that are very useful if you work on the terminal a lot. Many of the cool ones are not enabled by default – this is a small list of the configuration settings that I use to make my terminal usage more productive.

This is part 3 of the Customizing the Terminal series. Already published posts in this series are…

• Customizing the Terminal: The Prompt
• Customizing the Terminal: Create Useful Aliases

1. Case Correction

I like to title case my folders and files’ names. The folders in my home are ‘Scripts’, ‘Documents’, ‘Temp’ etc. The first character is in upper case. But when I work on the command line, I don’t always remember to uppercase the first character when trying to cd into a folder. Consequently, the tabbing will not work. Fortunately, there is an option that auto corrects the case for you. Just open a terminal and type in this command…

shopt -s nocaseglob

Other useful shopt option are…

cdspell

Corrects typos in your file/directory name.

histappend

Makes sure that histories in multiple simultaneous shells don’t overwrite each other.

2. Select Which Commands to Store in History

By default, all commands you type in are stored in the history. You can pick and chose the commands you want to store by putting the option…

export HISTCONTROL=ignorespace

in your ~/.bash_profile file. This will make sure that bash don’t store any command beginning with the space character. So if you want bash to forget that you typed in ‘ls’, just type in ‘ ls’(<space>ls).

3. Don’t Store Duplicate Commands in your History

As I said earlier, all commands you type are stored – even the duplicate ones. You can prevent this by putting this text in your .bash_profile file…

export HISTCONTROL=ignoredups

If you want to ignore spaced commands and want to prevent storing of duplicate commands, use the option…

export HISTCONTROL=ignoreboth

4. Auto-complete Command from History

Picture this – you type in ‘ssh’ and press the ‘Page Up’ key – and bash automatically fetches the last command that starts with ssh – and completes the command for you. Well, its possible – add the following line in your ‘.bash_profile’ file…

export INPUTRC=$HOME/.inputrc

Now, create a file called .inputrc in your home and enter this into it…

#Page up/page down
"\e[5~": history-search-backward
"\e[6~": history-search-forward

Yes, I am aware of the up Ctrl+R trick – that comes in the next post.

5. Infinite History

You can increase or decrease the size of the history by adding this line in the .bash_profile file…

export HISTSIZE=500
export HISTFILESIZE=500

This will limit the commands to be stored in the history to 500. If you want to remove the limit use these lines…

unset HISTSIZE
unset HISTFILESIZE

There is a good chance that this will make your history file quite huge – use with care.

Please share your configuration settings for bash in the comments.

Related Links

• shopt – Linux Command
• shopt (shell options) – Bash
• Linux Tips: take control of your bash_history
• 15 Examples To Master Linux Command Line History

This is part two of the ‘Customizing the Terminal’ series. Part one is ‘Customizing the Terminal: The Prompt‘. In this part, we’ll see how to create aliases to make working in the console easier.

How To Create an Alias

You can create a temporary alias using this command…

alias new_name='old command'

This will stop working when you exit the terminal. If you want to make the alias permanent, put the same command in your ~/.bashrc file.

There is another way to create an alias – create a executable file and place it in a folder in your path. This is not technically an alias – but it works the same way. I use this for alias that tend to change often. Its easier to find a file in a folder and edit it. YMMV.

My Aliases

This is a incomplete list of the aliases I use. Feel free to copy them to your .bashrc file.

Quick Directory Jumps

Create an alias to jump to folders you have to visit often. This is my list…

alias www='cd /var/www/html'
alias e='cd /mnt/x'

Relative Jumps

The above jumps are absolute jumps – relative jumps are possible too…

alias ..='cd ..'
alias ...='cd ../..'
alias ....='cd ../../..'
alias .....='cd ../../../..'

Some prefer this syntax…

alias ..='cd ..'
alias ..2='cd ../..'
alias ..3='cd ../../..'
alias ..4='cd ../../../..'

Often Used Commands

If you use some commands a lot, create smaller alternative for it…

alias x='exit'
alias q='exit'
alias rmdir='rm –rf'

Many of my own scripts are also alias’ed this way…

alias bk='perl "/home/binnyva/Scripts/Perl/Maintenance/Rsync Backup/RsyncBackup.pl"'
alias rbk='perl "/home/binnyva/Scripts/Perl/Maintenance/Rsync Backup/RsyncRemoteBackup.pl"'
alias nbk='perl "/home/binnyva/Scripts/Perl/Maintenance/Rsync Backup/RsyncNetworkBackup.pl"'
alias bdb='perl "/home/binnyva/Scripts/Perl/Maintenance/Database Backup/Dbbackup.pl"'

Complex Commands

Create a short version of long and complex command using alias…

alias gitstat='git status | perl -pe "exit if(/Untracked files\:/)"'
alias ra='ruby script/server'
alias wikipedia='cd /mnt/x/Data/Wikipedia/mywiki; firefox "http://localhost:8001/"; python manage.py runserver 8001; '
alias sup='svn update'

and more.

Command Changes

When I came from Windows to Linux, I was used to the dos commands – but not to the linux’s mv,cp commands. So I used to have aliases for those(I don’t have these now)

alias move='mv'
alias copy='cp'
alias ren='mv'
alias del='rm'

If you go from Red Hat/Fedora to Debian/Ubuntu(or vise versa), you can set up a few alias to make the change easier…

alias yum='apt-get'

You can get a lot of ideas for more aliases by looking at others .bashrc files.

Now tell me you aliases…

Most Linux ‘gurus’ spend a lot of time working in the terminal. If you belong to that group, this post is for you. This is a tutorial to configure the terminal prompt to the best possible value for your use. Note: This tutorial is for bash users – these instructions will not work in other shells.

The Prompt

You must have seen the prompt if you have use the terminal – it is the first few characters in each line. Usually, it will be…

[username@localhost] ~ $

In this case, the user is shown three piece of information in the prompt –

• Username of the current user
• Hostname
• Current folder name

This post will show you how to customize this prompt to your needs.

Editing the Prompt

Editing the prompt is very simple – you just have to edit a shell variable. To see the current prompt’s value, open a shell and type the command…

echo $PS1

The result will be something like this(in Ubuntu)…

binnyva@binlap:~$ echo $PS1
\[\e]0;\u@\h: \w\a\]${debian_chroot:+($debian_chroot)}\u@\h:\w\$

Which is functionally the same as…

\u@\h:\W\$ 

To edit this variable, run the command…

export PS1=<New Prompt Value>

Most desktop systems don’t need the username and hostname in the prompt – this is only relevent if your are connected to a remote system. So the first thing to do, if you are on a desktop system, is to remove those two. To do that, run the command…

export PS1="[\W]\$ "

This will change the prompt in the current terminal. To make it permanent, edit the ~/.bashrc and set the PS1 variable there. Just add this line at the end of the file…

export PS1="[\W]\$ "

A Better Prompt

Currently, the prompt has the basename of the current working directory. That is, if we are in ‘~/Sites/Lindesk/posts’, the prompt will be ‘[posts]$ ‘. This is good enough for most people. But I have a problem with this. If I go to another folder, say, ‘~/Sites/OpenJS/posts’, the prompt is still ‘[posts]$ ‘. The prompt is a bit ambiguous in this case. This can be done using a different character – in this case \w(small ‘w’ – the default was capital ‘W’).

[posts]$ export PS1="[\w]$ "
[~/Sites/OpenJS/posts]$ _

This is nice – but you will have a problem if the directory you are in is several levels deep. It might be something like this…

[/var/www/html/sites/Lindesk/lindesk.com/wp-content/plugins/eventr/langs]$ _

That’s long – and inconvenient. There are better ways of doing this.

Show the Beginning and the End.

A better way of doing this is to cut of a part of the folder – so the above path will look something like…

[/var/www/html.../eventr/langs] $ _

This option will show the first 15 characters of the path and then the last 15 characters – if the directory path is bigger than 30 characters. To enable this mode, open up the file ~/.bashrc and add this code…

PROMPT_COMMAND='DIR=`pwd|sed -e "s!$HOME!~!"`; if [ ${#DIR} -gt 30 ]; then CurDir=${DIR:0:12}...${DIR:${#DIR}-15}; else CurDir=$DIR; fi'
PS1="[\$CurDir] \$ "

The First Character of Each Directory

There is yet another method – I got this idea from the fish shell. In this approach, the big path will appear as…

[/v/w/h/s/L/l/w/p/e/langs] $ _

In this option, only the first character of each parent folder will be shown. Only the base folder name will be shown entirely. This is the approach I use. If you want to use this, open the ~/.bashrc file and add this…

PROMPT_COMMAND='CurDir=`pwd|sed -e "s!$HOME!~!"|sed -re "s!([^/])[^/]+/!\1/!g"`'
PS1="[\$CurDir] \$ "

Prompt Variables

The other values you can insert into the prompt are…

\d

the date in “Weekday Month Date” format (e.g., “Tue May 26″)

\D{format}

the format is passed to strftime(3) and the result is inserted into the prompt string; an empty format results in a locale-specific time representation. The braces are required

\e

an ASCII escape character (033)

\h

the hostname up to the first ‘.’

\H

the hostname

\j

the number of jobs currently managed by the shell

\l

the basename of the shell’s terminal device name

\n

newline

\r

carriage return

\s

the name of the shell, the basename of $0 (the portion following the final slash)

\t

the current time in 24-hour HH:MM:SS format

\T

the current time in 12-hour HH:MM:SS format

\@

the current time in 12-hour am/pm format

\A

the current time in 24-hour HH:MM format

\u

the username of the current user

\v

the version of bash (e.g., 2.00)

\V

the release of bash, version + patch level (e.g., 2.00.0)

\w

the current working directory, with $HOME abbreviated with a tilde

\W

the basename of the current working directory, with $HOME abbreviated with a tilde

\!

the history number of this command

\#

the command number of this command

\$

if the effective UID is 0, a #, otherwise a $

\nnn

the character corresponding to the octal number nnn

\\

a backslash

\[

begin a sequence of non-printing characters, which could be used to embed a terminal control sequence into the prompt

\]

end a sequence of non-printing characters

I have a small but very useful site called txt. Its a collection of code snippets, Linux commands and other such tidbits of information. The posts will be minimal and often crude. The purpose of that site is just to help me remember the information. To make it easier for me to look up the commands later.

For example, say that I need to remove all subversion information from a folder. That means deleting the ‘.svn’ folders in the current folder and all the folders under it. I have used this command before and have saved it to the txt site. So all I have to do is look up the tag that may have this command – in this case, the svn tag.

Soon, I get the page about removing SVN data from a folder. Nifty, huh?

The purpose of this post is two fold. First, I want to introduce you to my txt site – and hopefully get more traffic for that site. Second, and more important purpose is to get you intrested in this idea – to get a similar site for yourself. I saved a lot of time by using that site. Because its online, I was able to use my commands even when away from my computer. And its helpful for others as well.

You can see the reasons for creating the txt site here…

• Saving Code Snippets – Part 1
• Saving Code Snippets – Part 2

If you want to create a similar site, just go to WordPress and register for a new site. Trust me, its easy. If you have a similar system, please let me know – post a comment.