Restricted Shells (UNIX in a Nutshell: System V Edition) 4.8. Restricted Shells Restricted shells can be invoked in any of the following ways: rksh Korn shell ksh -r set -r /usr/lib/rsh Bourne shell set -r Restricted shells can also be set up by supplying the full pathname to rksh or rsh in the shell field of /etc/passwd or by using them as the value for the SHELL variable. Restricted shells act the same as their nonrestricted counterparts, except that the following are prohibited: Changing directory (i.e., using cd). Setting the PATH variable. rksh also prohibits setting ENV and SHELL. Specifying a / for command names or pathnames. Redirecting output (i.e., using > and >>). ksh also prohibits the use of <>. Adding new built-in commands (ksh93). Shell scripts can still be run, since in that case the restricted shell calls ksh or sh to run the script. This includes the /etc/profile, $HOME/.profile, and $ENV files. Restricted shells are not used much in practice, as they are difficult to set up correctly. 4.7. Invoking the Shell4.9. Built-in Commands Copyright © 2003 O'Reilly & Associates. All rights reserved.