Mar 2007
Bourne Again Shell offers a lot of power, flexibility and fun. Many new Unix
users do not realize the flexibility of the shell environment; indeed; many
new Unix users regard the shell as primitive
and too
restricted
: nothing could be further from the truth. With very little
time investment a new Unix user can learn how not to just make their work
environment in the shell more productive but even a little fun.
This text only discusses the bash shell and the latest versions of the bash shell.
In the old days (a few years ago...) shell prompts did not all act alike. Most earlier Unix shells did not react well to path munging, prompt changing or special characters. The modern Bash shell does not suffer issues like long path name buffer mangling, getting lost or not having enough built ins.
First and foremost to (most) users the shell prompt itself; there are 3 approaches to the shell prompt (in no particular order) for those who want to customize it:
Addressing each point is easiest...
The basic method of changing a prompt is by modifying the PS1
variable:
[jrf@vela:~]$ PS1="foo% " foo%
Bash has a builtin for handling the current working directory:
\w
On most Linux systems the current or print
working directory sequence is already defined in /etc/profile:
[jrf@vela:~]$ PS1="foo% " foo% PS1="foo \w $" foo ~ $cd docs foo ~/docs $
So there is the pwd capability, now onto what can be done with
the prompt string itself.
By default, Bash prints whoami at (&) hostname
if there is a default profile installed for Bash on the particular
system. Bash uses some more built in sequences to do so:
if [$PS1]; then if [ "$BASH" ]; then PS1='\u@\h:\w\$ ' else if [ "`id -u`" -eq 0 ]; then PS1='# ' else PS1='$ ' fi fi fi
Specifically, the \u and \h set the user and
hostname. What most folks like, however, is to use interesting looking
characters in the prompt. This is none to difficult to do:
PS1=":-) \h\w$ " :-) vela~/www/systhread.net/texts$
Colors in the shell are controlled by codes. Files and the prompt can
be colorized, however, they are done differently. Files are colored by
using ls --color which can be aliased as
ls=`ls --color'. The default location of file color schemes
varies from system to system. To use individual colors first build a file
(or copy the default one) and put it in $HOME/.dir_colors.
Following is an example dircolors file:
COLOR tty OPTIONS -F -T 0 # Below, there should be one TERM entry for each termtype that is colorizable TERM linux TERM console TERM con132x25 TERM con132x30 TERM con132x43 TERM con132x60 TERM con80x25 TERM con80x28 TERM con80x30 TERM con80x43 TERM con80x50 TERM con80x60 TERM cons25 TERM xterm TERM rxvt TERM xterm-color TERM color-xterm TERM vt100 TERM dtterm TERM color_xterm TERM ansi TERM screen TERM screen.linux TERM kon TERM kterm TERM gnome TERM konsole EIGHTBIT 1 # Text color codes: # 30=black 31=red 32=green 33=yellow 34=blue 35=magenta 36=cyan 37=white # Background color codes: # 40=black 41=red 42=green 43=yellow 44=blue 45=magenta 46=cyan 47=white NORMAL 00 # global default, although everything should be something. FILE 00 # normal file DIR 00;36 # directory LINK 00;35 # symbolic link FIFO 40;33 # pipe SOCK 01;35 # socket BLK 40;32;00 # block device driver CHR 40;32;00 # character device driver ORPHAN 01;05;37;41 # orphaned syminks MISSING 01;05;37;41 # ... and the files they point to # This is for files with execute permission: EXEC 00;33 # List any file extensions like '.gz' or '.tar' that you would like ls # to colorize below. Put the extension, a space, and the color init string. # (and any comments you want to add after a '#') .cmd 00;32 # executables (bright green) .exe 00;32 .com 00;32 .btm 00;32 .bat 00;32 .sh 00;32 .csh 00;32 .tar 00;31 # archives or compressed (bright red) .tgz 00;31 .arj 00;31 .taz 00;31 .lzh 00;31 .zip 00;31 .z 00;31 .Z 00;31 .gz 00;31 .bz2 00;31 .bz 00;31 .tz 00;31 .rpm 00;31 .cpio 00;31 .jpg 00;35 # image formats .gif 00;35 .bmp 00;35 .xbm 00;35 .xpm 00;35 .png 00;35 .tif 00;35
To change a color, simply use the color values desired. Using the colors
requires an eval statement in a login file, for instance the
$HOME/.bashrc:
eval `dircolors $HOME/.dir_colors`
Colorizing the prompt is similar. The Bashish provides a good start
for the bits needed in $HOME/.bashrc:
DULL=0
BRIGHT=1
FG_BLACK=30
FG_RED=31
FG_GREEN=32
FG_YELLOW=33
FG_BLUE=34
FG_VIOLET=35
FG_CYAN=36
FG_WHITE=37
FG_NULL=00
BG_BLACK=40
BG_RED=41
BG_GREEN=42
BG_YELLOW=43
BG_BLUE=44
BG_VIOLET=45
BG_CYAN=46
BG_WHITE=47
BG_NULL=00
##
# ANSI Escape Commands
##
ESC="\033"
NORMAL="\[$ESC[m\]"
RESET="\[$ESC[${DULL};${FG_WHITE};${BG_NULL}m\]"
##
# Shortcuts for Colored Text ( Bright and FG Only )
##
# DULL TEXT
BLACK="\[$ESC[${DULL};${FG_BLACK}m\]"
RED="\[$ESC[${DULL};${FG_RED}m\]"
GREEN="\[$ESC[${DULL};${FG_GREEN}m\]"
YELLOW="\[$ESC[${DULL};${FG_YELLOW}m\]"
BLUE="\[$ESC[${DULL};${FG_BLUE}m\]"
VIOLET="\[$ESC[${DULL};${FG_VIOLET}m\]"
CYAN="\[$ESC[${DULL};${FG_CYAN}m\]"
WHITE="\[$ESC[${DULL};${FG_WHITE}m\]"
# BRIGHT TEXT
BRIGHT_BLACK="\[$ESC[${BRIGHT};${FG_BLACK}m\]"
BRIGHT_RED="\[$ESC[${BRIGHT};${FG_RED}m\]"
BRIGHT_GREEN="\[$ESC[${BRIGHT};${FG_GREEN}m\]"
BRIGHT_YELLOW="\[$ESC[${BRIGHT};${FG_YELLOW}m\]"
BRIGHT_BLUE="\[$ESC[${BRIGHT};${FG_BLUE}m\]"
BRIGHT_VIOLET="\[$ESC[${BRIGHT};${FG_VIOLET}m\]"
BRIGHT_CYAN="\[$ESC[${BRIGHT};${FG_CYAN}m\]"
BRIGHT_WHITE="\[$ESC[${BRIGHT};${FG_WHITE}m\]"
# REV TEXT as an example
REV_CYAN="\[$ESC[${DULL};${BG_WHITE};${BG_CYAN}m\]"
REV_RED="\[$ESC[${DULL};${FG_YELLOW}; ${BG_RED}m\]"
PROMPT_COMMAND='export ERR=$?'
To create a colorized prompt use the color names in the prompt where desired:
PS1="${BRIGHT_CYAN}[${CYAN}\u$@\h${WHITE}:\w${BRIGHT_CYAN}]${NORMAL}\$ ${RESET}"
Simple, functional and just a little fun.
(based on last 2 months log reports)
