Thursday, March 30, 2006


USAGE of su command


Substitute user identity
Run a command with substitute user and group id, allow one user to
temporarily become another user. It runs a command
(often an interactiveshell)
with the real and effective user id, group id, and supplemental
groups of a given USER
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su [*options*]... [*user* [*arg*]...]


`-c *COMMAND*'


Pass *COMMAND*, a single command line to run, to the shell
with a

`-c' option instead of starting an interactive shell.



Pass the `-f' option to the shell. This probably only makes
if the shell run is `csh' or `tcsh', for which the `-f' option

prevents reading the startup file (`.cshrc'). With Bourne-like

shells, the `-f' option disables file name pattern expansion

(globbing), which is not likely to be useful.




Make the shell a login shell. This means the following. Unset all

environment variables except `TERM', `HOME', and `SHELL'
(which are set as described above), and `USER' and
`LOGNAME' (which are

set, even for the super-user, as described above), and set `PATH'

to a compiled-in default value. Change to USER's home directory.

Prepend `-' to the shell's name, intended to make it read its

login startup file(s).




Do not change the environment variables `HOME', `USER',

or `SHELL'. Run the shell given in the environment variable

`SHELL' instead of the shell from USER's passwd entry, unless
user running `su' is not the superuser and USER's shell is

restricted. A "restricted shell" is one that is not listed in the

file `/etc/shells', or in a compiled-in list if that file does not

exist. Parts of what this option does can be overridden by

`--login' and `--shell'.

`-s *SHELL*'


Run *SHELL* instead of the shell from USER's passwd entry, unless

the user running `su' is not the superuser and USER's shell is

restricted (see `-m' just above).

If no USER is given, the default is `root', the super-user.

The shell to use is taken from USER's `passwd' entry, or `/bin/sh' if none
is specified there.

If USER has a password, `su' prompts for the password unless run by a user
with effective user id of zero (the super-user).

By default, `su' does not change the current directory. It sets the
environment variables `HOME' and `SHELL' from the password entry for
and if USER is not the super-user, sets `USER' and `LOGNAME' to USER.

By default, the shell is not a login shell. Any additional ARGs are passed
as additional arguments to the shell.

GNU `su' does not treat `/bin/sh' or any other shells specially (e.g., by
setting `argv[0]' to `-su', passing `-c' only to certain shells, etc.). `su'
can optionally be compiled to use `syslog' to report failed, and optionally
successful, `su' attempts. (If the system supports `syslog'.) However, GNU
`su' does not check if the user is a member of the `wheel' group; see
options above.

*"It was just like Romeo and Juliet, only it ended in tragedy" - Milhouse*

*Related Linux Bash commands*:

chroot <> - Run a command
with a
different root directory
id <> - Print user and group id's
logname <> - Print current
login name

*Equivalent Windows XP commands*:

SU <> - Switch User
In Windows 2000 - RUNAS /USER: CMD.
or in the GUI hold Shift, and right-click on an executable

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