16.10 The Restricted Shell 2========================= 3 4If Bash is started with the name `rbash', or the `--restricted' or `-r' 5option is supplied at invocation, the shell becomes restricted. A 6restricted shell is used to set up an environment more controlled than 7the standard shell. A restricted shell behaves identically to `bash' 8with the exception that the following are disallowed or not performed: 9 10 * Changing directories with the `cd' builtin. 11 12 * Setting or unsetting the values of the `SHELL', `PATH', `ENV', or 13 `BASH_ENV' variables. 14 15 * Specifying command names containing slashes. 16 17 * Specifying a filename containing a slash as an argument to the `.' 18 builtin command. 19 20 * Specifying a filename containing a slash as an argument to the `-p' 21 option to the `hash' builtin command. 22 23 * Importing function definitions from the shell environment at 24 startup. 25 26 * Parsing the value of `SHELLOPTS' from the shell environment at 27 startup. 28 29 * Redirecting output using the `>', `>|', `<>', `>&', `&>', and `>>' 30 redirection operators. 31 32 * Using the `exec' builtin to replace the shell with another command. 33 34 * Adding or deleting builtin commands with the `-f' and `-d' options 35 to the `enable' builtin. 36 37 * Using the `enable' builtin command to enable disabled shell 38 builtins. 39 40 * Specifying the `-p' option to the `command' builtin. 41 42 * Turning off restricted mode with `set +r' or `set +o restricted'. 43 44These restrictions are enforced after any startup files are read. 45 46When a command that is found to be a shell script is executed (*note 47Shell Scripts::), `rbash' turns off any restrictions in the shell 48spawned to execute the script. 49 50