The meaning of SU...

What does the command su mean?

I just want to see how many people actually know what it means....

According to the source code for su (line 138 onwards from su.c in shadow-4.0.3):

/*
 * su - switch user id
 *
 *      su changes the user's ids to the values for the specified user.  if
 *      no new user name is specified, "root" is used by default.
 *
 *      The only valid option is a "-" character, which is interpreted as
 *      requiring a new login session to be simulated.
 *
 *      Any additional arguments are passed to the user's shell. In
 *      particular, the argument "-c" will cause the next argument to be
 *      interpreted as a command by the common shell programs.
 */

$ su -p

Silly & Unnecessary Polls.

Originally Posted by gilead According to the source code for su

That isn't su original source code, su was written by Dennis Ritchie and Ken Thompson in 1971.

This command original meaning and purpose was "super user" (from AT&T internal Unix source code, version 1 to 6) but evolved to "substitute user" in version 7, when the su command was changed to allow becoming any account, just not root. Version 7 su manual page states

su  -  substitute user id temporarily

"switch user" is almost synonymous, but doesn't appear in any Unix documents, so it can't be the correct answer IMHO.

I would have actually answered Something Usable but apparently it wasn't among the choices, so I had to take the other option (if everybody answered the correct answer, this wouldn't be fun).

I love the way unix systems take the Donald Duck abbreviations into use, I just hoped there were more of them

I've always read it to be Subsitute user.

Facetious replies aside, I would probably say super user.

http://cm.bell-labs.com/cm/cs/who/dmr/man13.pdf pg 17

I've seen "switch user" and "substitute user" used a lot in Unix documentation, so I guess both are right.

As stated the original Unix command, which was the first to use this, was used to become the super user (root). In adopting this, Linux it appears to have applied a more generic application of the command to switch user.

The three answers are all valid:
- super-user was what the original unix command stands for, but never make it outside Bell Labs.
- substitute user is Unix version 7 definition, kept by all its descendants and sometimes but not always used as Synopsis in su manual pages.
- switch user is an alternative and technically valid definition found in Gnu su.c source code, which implement the same functionality as the version 7 Unix su. Gnu documentation is still using "substitute user" http://www.gnu.org/software/coreutil...#su-invocation.

I've always known it as Super User or switch user. Mainly cause $su by itself defaults to the (SUPER!!!)root but of course specifying $su <user> you can switch to other users . All the other names for it just confuses things.

Originally Posted by custangro What does the command su mean? I just want to see how many people actually know what it means....

SU = super user

Linux man pages (online : click) reads:

su - run a shell with substitute user and group IDs

And me stupid thought it meant Super User...

Soviet Union!

Shut Up?

As in, "How can we shut this (l)user up?"

$ su -
$ cd </home/luser/>
$ rm -r *