7.1 Invoking the Shell

The command interpreter for bash can be invoked as follows:

bash [options] [arguments]

bash can execute commands from a terminal (when -i is specified), from a file (when the first argument is an executable script), or from standard input (if no arguments remain or if -s is specified).

7.1.1 Options

Options that appear here with double hyphens also work when entered with single hyphens, but using double hyphens is standard coding procedure.

-, --

Treat all subsequent strings as arguments, not options.

-D, --dump-strings

For execution in non-English locales, dump all strings that bash translates.

--dump-po-strings

Same as --dump-strings, but uses the GNU gettext po (portable object) format suitable for scripting.

-c str

Read commands from string str.

--help

Print usage information and exit.

-i

Create an interactive shell (prompt for input).

-l, --login

Behave like a login shell; try to process /etc/profile on startup. Then process ~/.bash_profile, ~/.bash_login, or ~/.profile (searching for each file only if the previous file is not found).

--noediting

Disable line editing with arrow and control keys.

--noprofile

Do not process /etc/profile, ~/.bash_profile, ~/.bash_login, or ~/.profile on startup.

--norc

Do not process ~/.bashrc on startup.

--posix

Conform to POSIX standard.

-r, --restricted

Restrict users to a very secure, limited environment; for instance, they cannot change out of the startup directory or use the > sign to redirect output.

--rcfile file

Substitute file for .bashrc on startup.

-s

Read commands from standard input. Output from built-in commands goes to file descriptor 1; all other shell output goes to file descriptor 2.

-v, --verbose

Print each line as it is executed (useful for tracing scripts).

--version

Print information about which version of bash is installed.

-x

Turn on debugging, as described under the -x option to the set built-in command later in this chapter.

The remaining options to bash are listed under the set built-in command.

7.1.2 Arguments

Arguments are assigned, in order, to the positional parameters $1, $2, and so forth. If the first argument is an executable script, it is assigned to $0; then commands are read from it, and remaining arguments are assigned to $1, $2, and so on.