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(bashref.info)Printing a Prompt

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Controlling the Prompt
======================

   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:

`\a'
     A bell character.

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

`\e'
     An escape character.

`\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'
     A newline.

`\r'
     A carriage return.

`\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.

`\A'
     The 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 + 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.

`\\'
     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 (Note: Bash History
Facilities), while the command number is the position in the sequence
of commands executed during the current shell session.

   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 (Note: Bash Builtins).