RBASH

   1 6.10 The Restricted Shell
   2 =========================
   3
   4 If Bash is started with the name `rbash', or the `--restricted' or `-r'
   5 option is supplied at invocation, the shell becomes restricted.  A
   6 restricted shell is used to set up an environment more controlled than
   7 the standard shell.  A restricted shell behaves identically to `bash'
   8 with 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
  44 These restrictions are enforced after any startup files are read.
  45
  46 When a command that is found to be a shell script is executed (*note
  47 Shell Scripts::), `rbash' turns off any restrictions in the shell
  48 spawned to execute the script.
  49