6.3.3 Interactive Shell Behavior
When the shell is running interactively, it changes its behavior in
several ways.
-
Startup files are read and executed as described in Bash Startup Files.
-
Job Control (see section Job Control) is enabled by default. When job
control is in effect, Bash ignores the keyboard-generated job control
signals
SIGTTIN, SIGTTOU, and SIGTSTP.
-
Bash expands and displays
PS1 before reading the first line
of a command, and expands and displays PS2 before reading the
second and subsequent lines of a multi-line command.
-
Bash executes the value of the
PROMPT_COMMAND variable as a command
before printing the primary prompt, $PS1
(see section Bash Variables).
-
Readline (@pxref{Command Line Editing}) is used to read commands from
the user’s terminal.
-
Bash inspects the value of the
ignoreeof option to set -o
instead of exiting immediately when it receives an EOF on its
standard input when reading a command (see section The Set Builtin).
-
Command history (@pxref{Bash History Facilities})
and history expansion (@pxref{History Interaction})
are enabled by default.
Bash will save the command history to the file named by
$HISTFILE
when an interactive shell exits.
-
Alias expansion (see section Aliases) is performed by default.
-
In the absence of any traps, Bash ignores
SIGTERM
(see section Signals).
-
In the absence of any traps,
SIGINT is caught and handled
((see section Signals).
SIGINT will interrupt some shell builtins.
-
An interactive login shell sends a
SIGHUP to all jobs on exit
if the huponexit shell option has been enabled (see section Signals).
-
The ‘-n’ invocation option is ignored, and ‘set -n’ has
no effect (see section The Set Builtin).
-
Bash will check for mail periodically, depending on the values of the
MAIL, MAILPATH, and MAILCHECK shell variables
(see section Bash Variables).
-
Expansion errors due to references to unbound shell variables after
‘set -u’ has been enabled will not cause the shell to exit
(see section The Set Builtin).
-
The shell will not exit on expansion errors caused by var being unset
or null in
${var:?word} expansions
(see section Shell Parameter Expansion).
-
Redirection errors encountered by shell builtins will not cause the
shell to exit.
-
When running in POSIX mode, a special builtin returning an error
status will not cause the shell to exit (see section Bash POSIX Mode).
-
A failed
exec will not cause the shell to exit
(see section Bourne Shell Builtins).
-
Parser syntax errors will not cause the shell to exit.
-
Simple spelling correction for directory arguments to the
cd
builtin is enabled by default (see the description of the cdspell
option to the shopt builtin in The Shopt Builtin).
-
The shell will check the value of the
TMOUT variable and exit
if a command is not read within the specified number of seconds after
printing $PS1 (see section Bash Variables).
