What's the difference between logging in as SU versus SU - root?
On another note: I'm glad to join this forum. Hopefully I'll learn a great deal. I'm not extremely new to Bash, however, I use it very little. I'm trying to learn more about scripting and such for adding scripted tasks into Crontab. I know how to use crontab, my dilemma is actually creating the scripts to execute.
Note that unix commands are in lower carriage. The su - root command starts a new Shell and executes root's profile . Without the - it doesn't. This is described at length in man su .
All this time, I assumed su = super user? As a result, logged the "root" user? Rather, it's "switch user?"
Yes, see this page:
Man Page for su (OpenSolaris Section 1m) - The UNIX and Linux Forums
su - become superuser or another user
Yes. There are as many interpretations for the command name as we want. According to Wikipedia:
The su command, also referred to as super user[1] substitute user, spoof user, set user or switch user, allows a computer operator to change the current user account associated with the running virtual console.
The manual page from my system uses "subtitute use":
The su command means Switch User . Not everything on Wikipedia is accurate. Admittedy the phrase does not appear in man su .
The original name is obscure, and this is the same with many Unix commands. dd(1) is a classical example. What is the meaning of the name dd? And yes, Wikipedia is not accurate. But one cannot just state: "the phrase does not appear in man su", since there are many implementations of the su(1) command, and so, many different man pages. The Mac OS X man page for su, for example, defines the command name as "substitute user identity" ( https://developer.apple.com/library/mac/\#documentation/Darwin/Reference/ManPages/man1/su.1.html ). Same for the FreeBSD 9.0 man page. Some man pages will not say anything, like you said - this is the case of many Linux man pages for this command, like the man page found in the Slackware 13.37.0. But the man page for the GNU version of su found in Suse will use the term "substitute user" much like the FreeBSD and OS X do. Anyway, the "semantics" is the same for every name: set, switch, substitute. Every name will mean the same thing.
The original name is not obscure but well known.
The first "su" implementation was written by Dennis Ritchie and Ken Thompson in 1971. From Unix version 1 to 6, this command meaning and purpose was "become super user".
eg: http://minnie.tuhs.org/cgi-bin/utree.pl?file=V5/usr/source/s2/su.c
/* su -- become super-user */
char password[100];
char pwbuf[100];
int ttybuf[3];
main()
{
Its manual page stated:
NAME su -- become privileged user
SYNOPSIS su password
DESCRIPTION su allows one to become the super-user, who has
all sorts of marvelous powers.
However, in version 7, the su command evolved to allow any account to be passed as an option. "su" started then to mean "substitute user".
Version 7 su manual page states
NAME
su - substitute user id temporarily
SYNOPSIS
su [ userid ]
"switch user" appeared only later, mostly in Gnu documents or source code, as a synonym of "substitute user.
How wrong could I be? The primary definition in HP-UX man su is switch user with subdefinitions set user and superuser .
I was reading the default man su page from unix.com at the time.