RSH(8) Maintenance Commands and Procedures RSH(8)
NAME
rsh, restricted_shell - restricted shell command interpreter
SYNOPSIS
/usr/lib/rsh [
-acefhiknprstuvx] [
argument]...
DESCRIPTION
rsh is a limiting version of the standard command interpreter
sh,
used to restrict logins to execution environments whose capabilities
are more controlled than those of
sh (see
sh(1) for complete
description and usage).
When the shell is invoked, it scans the environment for the value of
the environmental variable,
SHELL. If it is found and
rsh is the file
name part of its value, the shell becomes a restricted shell.
The actions of
rsh are identical to those of
sh, except that the
following are disallowed:
o changing directory (see
cd(1)),
o setting the value of $
PATH,
o specifying path or command names containing
/,
o redirecting output (
> and
>>).
The restrictions above are enforced after
.profile is interpreted.
A restricted shell can be invoked in one of the following ways:
1.
rsh is the file name part of the last entry in the
/etc/passwd file (see
passwd(5));
2. the environment variable
SHELL exists and
rsh is the file
name part of its value; the environment variable
SHELL needs to be set in the
.login file;
3. the shell is invoked and
rsh is the file name part of
argument 0;
4. the shell is invoked with the
-r option.
When a command to be executed is found to be a shell procedure,
rsh invokes
sh to execute it. Thus, it is possible to provide to the end-
user shell procedures that have access to the full power of the
standard shell, while imposing a limited menu of commands; this
scheme assumes that the end-user does not have write and execute
permissions in the same directory.
The net effect of these rules is that the writer of the
.profile (see
profile(5)) has complete control over user actions by performing
guaranteed setup actions and leaving the user in an appropriate
directory (probably
not the login directory).
The system administrator often sets up a directory of commands (that
is,
/usr/rbin) that can be safely invoked by a restricted shell. Some
systems also provide a restricted editor,
red.
EXIT STATUS
Errors detected by the shell, such as syntax errors, cause the shell
to return a non-zero exit status. If the shell is being used non-
interactively execution of the shell file is abandoned. Otherwise,
the shell returns the exit status of the last command executed.
SEE ALSO
Intro(1),
cd(1),
login(1),
rsh(1),
sh(1),
exec(2),
passwd(5),
profile(5),
attributes(7)NOTES
The restricted shell,
/usr/lib/rsh, should not be confused with the
remote shell,
/usr/bin/rsh, which is documented in
rsh(1).
November 1, 1993 RSH(8)
