TwistedCode

LS_COLORS Explained

noreply@blogger.com (Derek) — Sun, 13 Apr 2008 05:18:00 +0000

In my previous article I showed you how to make the ls command display colored output; now I am going to show you how to customize what colors get displayed. We are going to use the LS_COLORS environment variable to accomplish this task.

You can change your LS_COLORS environment variable by setting it in your $HOME/.bash_profile or $HOME/.bashrc file. The syntax for LS_COLORS is as follows:

LS_COLORS='di=1:fi=0:ln=31:pi=5:so=5:bd=5:cd=5:or=31:*.deb=90'

The parameters for LS_COLORS (di, fi, ln, pi, etc) refer to different file types:

di	Directory
fi	File
ln	Symbolic Link
pi	Fifo file
so	Socket file
bd	Block (buffered) special file
cd	Character (unbuffered) special file
or	Symbolic Link pointing to a non-existent file (orphan)
mi	Non-existent file pointed to by a symbolic link (visible when you type ls -l)
ex	File which is executable (ie. has 'x' set in permissions).

The *.deb=90 parameter in the example above tells ls to display any files ending with a .deb extension using the color specified, 90 or dark grey in this case. This can be applied to any types of files (eg. you could use *.jpg=33 to make JPEG files appear orange). Any number of parameters can go into the LS_COLORS variable, as long as the parameters are separated by colons.

Color Codes

Through trial and error I worked out the color codes for LS_COLORS to be:

0 =	Default Colour
1 =	Bold
4 =	Underlined
5 =	Flashing Text
7 =	Reverse Field
31 =	Red
32 =	Green
33 =	Orange
34 =	Blue
35 =	Purple
36 =	Cyan
37 =	Grey
40 =	Black Background
41 =	Red Background
42 =	Green Background
43 =	Orange Background
44 =	Blue Background
45 =	Purple Background
46 =	Cyan Background
47 =	Grey Background
90 =	Dark Grey
91 =	Light Red
92 =	Light Green
93 =	Yellow
94 =	Light Blue
95 =	Light Purple
96 =	Turquoise
100 =	Dark Grey Background
101 =	Light Red Background
102 =	Light Green Background
103 =	Yellow Background
104 =	Light Blue Background
105 =	Light Purple Background
106 =	Turquoise Background

These codes can also be combined with one another:

di=5;34;43

Setting the LS_COLORS di parameter to the above example will make directories appear in flashing blue text with an orange background (just because flashing text is available doesn't mean you should use it!)

Customizing the colors that ls uses to display it's output can make sifting through your filesystem a very easy task. If you have any questions post them in the comments below.

Google Custom Time

noreply@blogger.com (Derek) — Tue, 01 Apr 2008 13:39:00 +0000

Today when I logged into my Gmail account I was presented with a New! feature; Gmail Custom Time

I have to give props to Google, they have a great sense of humor. Google was even able to throw in a reference to the coveted Flux Capacitor, it is a must read!

Gmail Custom Time

Customizing Your Bash Prompt

noreply@blogger.com (Derek) — Fri, 28 Mar 2008 15:11:00 +0000

I came to OS X from the wonderful world of Linux; upon doing so I really missed my customized terminal prompt; after all, the default Mac OS X prompt is really boring and blah.

Customizing the default shell prompt not only makes the terminal that much more exciting, it will also help you remember which system you are currently on and the directory you are about to run a command in (Yea!, no more incessant pwd commands). This is especially useful for those late night pesky phone calls letting you know that you have to come into work early, really, really early; to fix the server that the underpaid incompetent third string sysadmin was supposed to be watching! Arriving on site with multiple windows open mixed with sleep deprivation can have some very devastating results. Running shutdown or init in the wrong window can really hurt.

Bash Prompt Variables

The primary Bash shell prompt is customized by setting the $PS1 shell environment variable. In order to see what your current prompt is set to you must echo $PS1:

echo $PS1

Characters prefixed by a backslash (\) are actually variables that get expanded. Here is a list of all Bash prompt variables as described in the PROMPTING section of the BASH(1) man page.

`\a`	an ASCII bell character (07)
`\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 full hostname
`\j`	the number of jobs currently managed by the shell
`\l`	the basename of the shells 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

Setting Your Prompt

Set your new prompt by manipulating the $PS1 variable.

export PS1='\h:\W \u\$ '

That would make your prompt look like this:

hostname:~ username$

To keep your settings for the next Bash shell, place a line in your $HOME/.bashrc that looks like this:

PS1='\h:\W \u\$ '

Mac users note the following
Due to the way OS X and the Terminal application handle command emulation you have to create the file $HOME/.bash_profile and enter the following line:

source ~/.bashrc

Once you have done this every Terminal window you open up will have your custom prompt.

Other Variables

$PS1 is not the only shell variable that affects your prompt. $PS2 is the secondary prompt. The secondary prompt shows up in command line loops:

hostname:~ username$ export PS2="--> "
hostname:~ username$ for x in $(seq 3); do
--> echo $x
--> done
1 2 3
hostname:~ username$

$PS3 and $PS4 also exist. From the Bash Reference Manual:

`PS1`	the primary prompt string. The default value is `'\s-\v\$ '`.
`PS2`	the secondary prompt string. The default value is `'> '`.
`PS3`	the value of this variable is used as the prompt for the select command. If this variable is not set, the select command prompts with `'#? '`.
`PS4`	the value is the prompt printed before the command line is echoed when the `-x` option is set (see The Set Builtin). The first character of `PS4` is replicated multiple times, as necessary, to indicate multiple levels of indirection. The default is `'+ '`.
`PROMPT_COMMAND`	if set, the value is interpreted as a command to execute before the printing of each primary prompt (`$PS1`). `$PROMPT_COMMAND` can be used in clever ways to run a command before each primary prompt display. See below for an example

hostname:~ username$ export PROMPT_COMMAND='echo -n "$(uptime | cut -d',' -f1) "'
14:33:01 up 6 days hostname:~ username$

Time to Colorize!

Some of you might want to present your shell prompt using color. This is especially useful for privileged shells. Lets make the root shell display using red:

hostname:~ username$ export PS1="\e[01;31m\h:\W \u\$ \e[00m"

This might look a little confusing so let's break it down.

`\e[`	is the Escape Character sequence (you can also use `\[\033[`)
`01;31m`	Sets the color to light (`01`) red (`31`)
`\h:\W \u\$`	Prints `hostname:(current directory) username$`
`\e[`	Escape Character sequence
`00m`	Clears all color (no color after this point)

In this example if your username is alex, your hostname is 'hades', and you are currently in your $HOME directory the resulting prompt will look like:

hades:~ alex$

Bash Color Escape Codes

Use any of the following escape codes between \e[ and m to colorize text in Bash:

Black	`0;30`
Dark Gray	`1;30`
Blue	`0;34`
Light Blue	`1;34`
Green	`0;32`
Light Green	`1;32`
Cyan	`0;36`
Light Cyan	`1;36`
Red	`0;31`
Light Red	`1;31`
Purple	`0;35`
Light Purple	`1;35`
Brown	`0;33`
Yellow	`1;33`
Light Gray	`0;37`
White	`1;37`

My custom prompt...

Just in case you were wondering what I have set my prompt to here we go:

PS1='\[\033[01;32m\]\u\[\033[01;34m\]::\[\033[01;31m\]\h \[\033[00;34m\]{ \[\033[01;34m\]\w \[\033[00;34m\]}\[\033[01;32m\]-> \[\033[00m\]'

Which looks like this:

The PS1 string does not span multiple lines. I decided to use \[033[ instead of \e[ to maximize compatibility between different terminals (I like to take my custom shell everywhere I go). If you would like a breakdown of my prompt feel free to ask in the comments below.

References
Bash Reference Manual
Bash Prompt Howto

Colored ls Output

noreply@blogger.com (Derek) — Wed, 26 Mar 2008 20:59:00 +0000

Unix uses the ls command to list the contents of a directory. By default ls displays all directories and files the same way, leaving you without the ability to quickly determine what type of files you are looking at (in Unix everything is a file). Here is an screenshot showing the default output of ls on OS X:

ls has the ability to color code different file types by passing the --color option to ls. For example, type the following command at your shell prompt to see colorized output:

$ ls --color

Here is what that command looks like:

If you get an error statement after running the last command then you most likely do not have the GNU version of ls installed. You can download the GNU version of ls by downloading and installing the GNU Coreutils package for your OS.

If you are not using xterm as your terminal you may have to set the TERM environment variable to xterm or xterm-color. The TERM setting you choose will depend on your OS and distribution. You change your TERM variable by running the following:

export TERM=xterm-color

export TERM=xterm

To make your TERM environment variable persistent you add either of the commands above to your $HOME/.bash_profile or $HOME/.bashrc just like we did for the alias definition.

To customize the color ls displays you must modify the LS_COLORS environment variable. LS_COLORS is formatted as a string of variables separated by colons. Changing LS_COLORS is out of the scope of this howto. I have explained the LS_COLORS variable in detail here.

Creating an Alias

Typing ls --color everytime you need to use ls seems a little tedious, that is where the wonderful alias command comes in. alias allows you to create a shorthand definition to replace a command or a series of commands. To create an alias you can either put your alias definition in the $HOME/.bash_profile or $HOME/.bashrc which is persistent across multiple logins and shells or you can specify an alias definition at the command line. Examples of both are below:

Adding an alias definition to $HOME/.bash_profile

$ echo "alias ls='ls --color'" >> $HOME/.bash_profile

If you want to put the alias definition in $HOME/.bashrc just substitute it instead of $HOME/.bash_profile in the example above.

Create an alias definition that will only be valid for your current shell session perform the following:

$ alias ls='ls --color'

Now whenever you use ls it will use colored output.