Section 5.1. Invoking the Shell

5.1. 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).

5.1.1. 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).

-init-file file

Substitute file for .bashrc on startup.

-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

Don't process /etc/profile , ~/.bash_profile , ~/.bash_login , or ~/.profile on startup.

-- norc

Don't process ~/.bashrc on startup.

-- posix

Conform to POSIX standard.

-r, -- restricted

Restrict users to a very secure, limited environment; for instance, they can't 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.

5.1.2. 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.