Linux BASH syntax : prompt variable

The value of the variable PROMPT_COMMAND is examined just before Bash prints each primary prompt.

If PROMPT_COMMAND is set and has a non-null value, then the value is executed just as if it had been typed on the command line.

In addition, the following table describes the special characters which can appear in the prompt variables:

\d   The date, in "Weekday Month Date" format (e.g., "Tue May 26"). 

\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. 

\s   The name of the shell, the basename of $0 (the portion following 
    the final slash). 

\t   The time, in 24-hour HH:MM:SS format. 
\T   The time, in 12-hour HH:MM:SS format. 
\@   The time, in 12-hour am/pm format. 

\u   The username of the current user. 

\v   The version of Bash (e.g., 2.00) 

\V   The release of Bash, version + patchlevel (e.g., 2.00.0) 

\w   The current working directory. 
\W   The basename of $PWD. 

\!   The history number of this command. 
\#   The command number of this command. 

\$   If the effective uid is 0, #, otherwise $. 

\nnn   The character whose ASCII code is the octal value nnn. 

\n   A newline. 
\r   A carriage return. 
\e   An escape character. 
\a   A bell character.
\\   A backslash. 

\[   Begin a sequence of non-printing characters. This could be used to embed 
     a terminal control sequence into the prompt. 

\]   End a sequence of non-printing characters.

The command number and the history number are usually different: the history number of a command is its position in the history list, which may include commands restored from the history file, while the command number is the position in the sequence of commands executed.

After the string is decoded, it is expanded via parameter expansion, command substitution, arithmetic expansion, and quote removal, subject to the value of the promptvars shell option.

Related commands:

env - Display, set, or remove environment variables
export - Set an environment variable

Prompt examples - from IBM DeveloperWorks.

Windows equivalent commands:

PROMPT - Change the command prompt