6.3.3 Interactive Shell Behavior
When the shell is running interactively, it changes its behavior in
- Startup files are read and executed as described in Bash Startup Files.
- Job Control (see Job Control) is enabled by default. When job
control is in effect, Bash ignores the keyboard-generated job control
- 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 expands and displays
PS0 after it reads a command but before
See Controlling the Prompt, for a complete list of prompt
string escape sequences.
- Bash executes the value of the
PROMPT_COMMAND variable as a command
before printing the primary prompt,
(see Bash Variables).
- Readline (see Command Line Editing) is used to read commands from
the user’s terminal.
- Bash inspects the value of the
ignoreeof option to
instead of exiting immediately when it receives an
EOF on its
standard input when reading a command (see The Set Builtin).
- Command history (see Bash History Facilities)
and history expansion (see History Interaction)
are enabled by default.
Bash will save the command history to the file named by
when a shell with history enabled exits.
- Alias expansion (see Aliases) is performed by default.
- In the absence of any traps, Bash ignores
- In the absence of any traps,
SIGINT is caught and handled
SIGINT will interrupt some shell builtins.
- An interactive login shell sends a
SIGHUP to all jobs on exit
huponexit shell option has been enabled (see Signals).
- The -n invocation option is ignored, and ‘set -n’ has
no effect (see The Set Builtin).
- Bash will check for mail periodically, depending on the values of the
MAILCHECK shell variables
(see 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 The Set Builtin).
- The shell will not exit on expansion errors caused by var being unset
or null in
(see 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 Bash POSIX Mode).
- A failed
exec will not cause the shell to exit
(see Bourne Shell Builtins).
- Parser syntax errors will not cause the shell to exit.
- Simple spelling correction for directory arguments to the
builtin is enabled by default (see the description of the
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
$PS1 (see Bash Variables).