MAC OS X : BASH Customize Your Terminal Prompt; A little Color, Invoke A Script & Other Prompt Options
Now, if you are new to BASH or have experience with BASH the PROMPT is very useful for information that can be conveyed to the user about the date/time, login id, jobs running and several other options. Furthermore, the prompt can be set to display colors to highlight prompt areas to vividly display this information to the user.
Lets start out with describing the Prompt Environment value:
Simply, PS1 and PS2 are prompt environment values that MAC OS X BASH uses (alot of this applies to other UNIX systems and the knowledge here can be transferred to Linux, HPUX, etc without very little change, if any) to customize how the terminal displays the prompt to the user. PS1 & PS2 are primary and secondary prompts! PS1's purpose as the primary prompt is to request commands from the user. The secondary prompt's purpose is to take further input from a command invoked from a PS1 prompt that request additional information. An example of a PS1 prompt is listed below:
The prompt above represents the PS1 environment variable. Let's disect the prompt to understand how this was customized:
| <Helios:sparc> 0 [02-12 08:57] ~ (0 Mb) ! |
Helios is the HOST name of the computer
":" colon is a character to seperate the Host from the User ID (Personal Preference)
sparc is the user id.
The 0 is the number of jobs the user has running in the background.
The Date & Time is self explanatory.
~ is the current directory
O Mb is the total amount of bytes representing all the files in the current directory.
There is the format of this customized prompt, now
| PS1="\n<\[\033[0;32m\]\h\[\033[0m\]:\[\033[0;37m\]\u\[\033[0m\]> \j [\$(date +%m-%d\" \"%H:%M)] \w (\[\033[0;36m\]\$(/Users/sparc/bin/TBytes.sh) Mb\[\033[0m\])\n! " |
\n is simply requesting a new line.
< just a character
\[ starts NON-PRINTING characters (Prepares to request color change)
\033[ escape sequence
0 uses default attribute [0 portion] for bold, underscore etc.
;32m sets the color
\] Ends the NON-PRINTING characters
The entire command is \[\033[0;32m\] Turns font color to blue
/h is the host
/u user
(date +%m-%d\" \"%H:%M) Turns font color to white
\$ Expands to the process ID of the shell. In a () subshell, in this case the date command is invoked to retrieve current Month/Day/Hour/Minute as seen below:
(date +%m-%d\" \"%H:%M)
\w current working directory (pwd)
\$(/Users/sparc/bin/TBytes.sh) is another subshell request to a script file that reads the number of bytes used by the files in the current directory. The script is below:
! cat ~/bin/TBytes.sh |
\[\033[0m\] This sequence puts the font color back to the original prompt color
\n New Line
! Character to present for prompt user for input.
The following escape sequences and decodings are below:
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\a |
an ASCII bell character (07) |
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\d |
thedatein "Weekday Month Date" format (e.g. Rue May 26) |
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\D{format} |
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the format is passed to strftime(3)andtheresultis |
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insertedinto the prompt string; an empty format results |
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in a locale-specific time representation.The braces are |
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required |
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\e |
an ASCII escape character (033) |
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\h |
the hostname up to the first `.' |
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\H |
the hostname |
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\j |
the number of jobs currently managed by the shell |
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\l |
the basename of the shell's terminal device name |
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\n |
newline |
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\r |
carriage return |
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\s |
thenameof the shell the basename of $0 (the portion following the final slash) |
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\t |
the current time in 24-hour HH:MM:SS format |
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\T |
the current time in 12-hour HH:MM:SS format |
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\@ |
the current time in 12-hour am/pm format |
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\A |
the current time in 24-hour HH:MM format |
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\u |
the username of the current user |
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\v |
the version of bash (e.g. 2.00) |
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\V |
the release of bash version + patchelvel (e.g. 2.00.0) |
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\w |
the current working directory |
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\W |
the basename of the current working directory |
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\! |
the history number of this command |
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\# |
the command number of this command |
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\$ |
if the effective UID is 0 a # otherwise $ |
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\nnn |
the character corresponding to the octal number nnn |
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\\ |
a backslash |
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\[ |
begin a sequence of non-printing characters which could |
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beusedtoembeda terminal control sequence into the |
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prompt |
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\] |
end a sequence of non-printing characters |
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PS1='[\u@TEST \w]\n \#\$ \n\ |
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\[\ |
end a sequence of non-printing characters |
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\e[1mBold Text\e[m\n\ |
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\e[4mUnderline Text\e[m\n\ |
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\e[5mBlink Text\e[m\n\ |
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\e[7mInverse Text\e[m\]\n\ |
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Should be normal text |
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Foreground colors: |
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\[\ |
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\e[0;30m |
Black\n\ |
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\e[0;31m |
Red\n\ |
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\e[0;32m |
Green\n\ |
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\e[0;33m |
Yellow\Orange\n\ |
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\e[0;34m |
Blue\n\ |
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\e[0;35m |
Magenta\n\ |
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\e[0;36m |
Cyan\n\ |
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\e[0;37m |
Light Gray\Black\n\ |
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\e[0;39m |
Default\n\ |
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Bright foreground colors: |
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\e[1;30m |
Dark Gray\n\ |
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\e[1;31m |
Red\n\ |
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\e[1;32m |
Green\n\ |
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\e[1;33m |
Yellow\n\ |
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\e[1;34m |
Blue\n\ |
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\e[1;35m |
Magenta\n\ |
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\e[1;36m |
Cyan\n\ |
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\e[1;37m |
White\n\ |
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\e[0;39m |
Default\n\ |
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Background Colors |
\e[m\] |
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\[\e[1;37m\e[40m: |
Black\e[0;49m\n\ |
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\e[41m: |
Red\e[0;49m\n\ |
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\e[42m: |
Green\e[0;49m\n\ |
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\e[43m: |
Yellow\Orange\e[0;49m\n\ |
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\e[44m: |
Blue\e[0;49m\n\ |
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\e[45m: |
Magenta\e[0;49m\n\ |
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\e[46m: |
Cyan\e[0;49m\n\ |
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\e[47m: |
Light Gray\Black\e[0;49m\n\ |
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\e[49m: |
Default\e[m\]\n' |
For more detail information from the terminal you can issue "man bash"
When you drag awk into it, why bother with grep and
for? awk does it all:
Klaus,