(features.info)Bash Variables

Bash Variables
==============

   These variables are set or used by bash, but other shells do not
normally treat them specially.

`HISTCONTROL'
`history_control'
     Set to a value of `ignorespace', it means don't enter lines which
     begin with a space or tab into the history list.  Set to a value
     of `ignoredups', it means don't enter lines which match the last
     entered line.  A value of `ignoreboth' combines the two options.
     Unset, or set to any other value than those above, means to save
     all lines on the history list.

`HISTFILE'
     The name of the file to which the command history is saved.

`HISTSIZE'
     If set, this is the maximum number of commands to remember in the
     history.

`histchars'
     Up to three characters which control history expansion, quick
     substitution, and tokenization (Note: History Interaction.).
     The first character is the "history-expansion-char", that is, the
     character which signifies the start of a history expansion,
     normally `!'.  The second character is the character which
     signifies `quick substitution' when seen as the first character on
     a line, normally `^'.  The optional third character is the
     character which signifies the remainder of the line is a comment,
     when found as the first character of a word, usually `#'.  The
     history comment character causes history substitution to be
     skipped for the remaining words on the line.  It does not
     necessarily cause the shell parser to treat the rest of the line
     as a comment.

`HISTCMD'
     The history number, or index in the history list, of the current
     command.  If `HISTCMD' is unset, it loses its special properties,
     even if it is subsequently reset.

`hostname_completion_file'
`HOSTFILE'
     Contains the name of a file in the same format as `/etc/hosts' that
     should be read when the shell needs to complete a hostname.  You
     can change the file interactively; the next time you attempt to
     complete a hostname, Bash will add the contents of the new file to
     the already existing database.

`MAILCHECK'
     How often (in seconds) that the shell should check for mail in the
     files specified in `MAILPATH'.

`PROMPT_COMMAND'
     If present, this contains a string which is a command to execute
     before the printing of each primary prompt (`$PS1').

`UID'
     The numeric real user id of the current user.

`EUID'
     The numeric effective user id of the current user.

`HOSTTYPE'
     A string describing the machine Bash is running on.

`OSTYPE'
     A string describing the operating system Bash is running on.

`FIGNORE'
     A colon-separated list of suffixes to ignore when performing
     filename completion A file name whose suffix matches one of the
     entries in `FIGNORE' is excluded from the list of matched file
     names.  A sample value is `.o:~'

`INPUTRC'
     The name of the Readline startup file, overriding the default of
     `~/.inputrc'.

`BASH_VERSION'
     The version number of the current instance of Bash.

`IGNOREEOF'
     Controls the action of the shell on receipt of an `EOF' character
     as the sole input.  If set, then the value of it is the number of
     consecutive `EOF' characters that can be read as the first
     characters on an input line before the shell will exit.  If the
     variable exists but does not have a numeric value (or has no
     value) then the default is 10.  If the variable does not exist,
     then `EOF' signifies the end of input to the shell.  This is only
     in effect for interactive shells.

`no_exit_on_failed_exec'
     If this variable exists, the shell will not exit in the case that
     it couldn't execute the file specified in the `exec' command.

`nolinks'
     If present, says not to follow symbolic links when doing commands
     that change the current working directory.  By default, bash
     follows the logical chain of directories when performing commands
     such as `cd' which change the current directory.

     For example, if `/usr/sys' is a link to `/usr/local/sys' then:
          $ cd /usr/sys; echo $PWD
          /usr/sys
          $ cd ..; pwd
          /usr

     If `nolinks' exists, then:
          $ cd /usr/sys; echo $PWD
          /usr/local/sys
          $ cd ..; pwd
          /usr/local

     See also the description of the `-P' option to the `set' builtin,
     Note: The Set Builtin.