Content-type: text/html Manpage of chgrpsh

chgrpsh

Section: User Commands (1)
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NAME

chgrpsh - fork a shell process or execute a command with a new set of process groups

SYNOPSIS

chgrpsh [ [+|-]groupname ] [-- cmd arg1 ... ]

DESCRIPTION

Chgrpsh forks a new user process in which the group vector has been changed under user control. Group name arguments preceded a '+' are added to the group vector; those preceded by '-' are removed. Trailing arguments without a '+' or '-' (or those following '--') are assumed to be a command and are executed. If no command is given an interactive shell is created.

Chgrpsh has two main purposes:

1.

Unix systems impose a limitation (generally from 8 to 32) on the number of groups a process can be in simultaneously. Chgrpsh relaxes this restriction somewhat by allowing you to create a shell process in which some groups have been replaced by others, thus keeping the total number of groups within the limitation while allowing you access to groups you have been authorized to join. This is particularly useful for instructors and teaching assistants who need to deal with class group protections when grading. For instance, it is not possible to be in all the groups cseXYZa, cseXYZb, ..., cseXYZz simultaneously. Chgrpsh can be used to create shells associated with a subset of these groups. E.g.

% chgrpsh +cseXYZa +cseXYZb ... +cseXYZf
%  < do some grading >
% exit
% chgrpsh +cseXYZg +cseXYZh ....
% < do more grading >
% exit

2.

When group membership changes are made, it can take up to an hour for those changes to propagate to the local /etc/group files of all machines. And any new groups that a user may acquire are not automatically added to existing login sessions, requiring the the user to log out and then log in again to use their new memberships. However, chgrpsh can be used to create a shell with any new groups immediately after the main group database has been updated. Thus if you need to exercise group rights very soon after you have been added to a group, simply use "chgrpsh +newgroup".

Other examples:

: chgrpsh -oldgroup +newgroup1 +newgroup2 emacs file
chgrpsh +agroup +bgroup

To determine what groups your process(es) are current using, use the standard groups(1) command.

CAVEATS

Chgrpsh tries to use a local cache of group membership information. If a group given as an argument is not in the local cache, chgrpsh will attempt to obtain your group memberships from the Unix group database. This behavior allows users to short-cut the propagation delay of /etc/group files created from database content. However, querying the database requires that you valid Kerberos credentials.

You will not be allowed to replace your login (/etc/passwd) group.

FILES

/etc/group
/etc/group.all
Unixgroups database

This document was created by man2html, using the manual pages.
Time: 22:48:39 GMT, October 10, 2006