Basic Linux command line question Post: 302993066

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Top Forums UNIX for Beginners Questions & Answers Basic Linux command line question Post 302993066 by drysdalk on Monday 6th of March 2017 12:19:17 PM

03-06-2017

Registered User

Hi,

OK, there are various things going here that perhaps need explaining. About the simplest way I can think of tackling your questions is to start with explaining what each of these commands actually does, which might help you understand what you're seeing a bit better.

pwd
This command will print out what's called your current working directory. Your working directory is the directory in the filesystem that you're in at the moment. You change directories with the..

cd
command. cd changes directories, and nothing else. So it's the command you use to change your working directory, and navigate around the filesystem.

su
The switch user command. Nearly always used as a regular user to switch to assume the permissions of the root user. root is the super-user account - that is, the account on a UNIX system that (usually) has full access to all directories and parts of the system, and has permission to run all commands.

Next, I think it would be helpful for you to realise there's a clear distinction between users and directories. Broadly speaking, every user on a UNIX system has one directory on the system reserved for their own use, called their home directory. Typing cd on its own will take you back to this home directory in almost all circumstances. But this home directory needn't have the same name as the user, and can be anything at all. Likewise, any directory on the system can take any name. Every directory on the filesystem will be owned by one particular user and one particular group.

Now, when you use su, the default behaviour will be to leave you in whatever directory you happen to be in at the time, rather than to switch you to the home directory of the user you're wanting to become. If you want it to do that (and more besides), try using the syntax su - instead. This will execute the full login environment of the user you're switching to, and so you will find your current working directory will change to their home directory.

Anyway, hope all this helps you to understand a bit more clearly what's going on here.

drysdalk

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LEARN ABOUT FREEBSD

tabs

TABS(1) 						    BSD General Commands Manual 						   TABS(1)

NAME

     tabs -- set terminal tabs

SYNOPSIS

     tabs [-n | -a | -a2 | -c | -c2 | -c3 | -f | -p | -s | -u] [+m[n]] [-T type]
     tabs [-T type] [+[n]] n1[,n2,...]

DESCRIPTION

     The tabs utility displays a series of characters that clear the hardware terminal tab settings then initialises tab stops at specified posi-
     tions, and optionally adjusts the margin.

     In the first synopsis form, the tab stops set depend on the command line options used, and may be one of the predefined formats or at regular
     intervals.

     In the second synopsis form, tab stops are set at positions n1, n2, etc.  If a position is preceded by a '+', it is relative to the previous
     position set.  No more than 20 positions may be specified.

     If no tab stops are specified, the ``standard'' UNIX tab width of 8 is used.

     The options are as follows:

     -n      Set a tab stop every n columns.  If n is 0, the tab stops are cleared but no new ones are set.

     -a      Assembler format (columns 1, 10, 16, 36, 72).

     -a2     Assembler format (columns 1, 10, 16, 40, 72).

     -c      COBOL normal format (columns 1, 8, 12, 16, 20, 55)

     -c2     COBOL compact format (columns 1, 6, 10, 14, 49)

     -c3     COBOL compact format (columns 1, 6, 10, 14, 18, 22, 26, 30, 34, 38, 42, 46, 50, 54, 58, 62, 67).

     -f      FORTRAN format (columns 1, 7, 11, 15, 19, 23).

     -p      PL/1 format (columns 1, 5, 9, 13, 17, 21, 25, 29, 33, 37, 41, 45, 49, 53, 57, 61).

     -s      SNOBOL format (columns 1, 10, 55).

     -u      Assembler format (columns 1, 12, 20, 44).

     +m[n], +[n]
	     Set an n character left margin, or 10 if n is omitted.

     -T type
	     Output escape sequence for the terminal type type.

ENVIRONMENT

     The LANG, LC_ALL, LC_CTYPE and TERM environment variables affect the execution of tabs as described in environ(7).

     The -T option overrides the setting of the TERM environment variable.  If neither TERM nor the -T option are present, tabs will fail.

EXIT STATUS

     The tabs utility exits 0 on success, and >0 if an error occurs.

SEE ALSO

     expand(1), stty(1), tput(1), unexpand(1), termcap(5)

STANDARDS

     The tabs utility conforms to IEEE Std 1003.1-2001 (``POSIX.1'').

HISTORY

     A tabs utility appeared in PWB UNIX.  This implementation was introduced in FreeBSD 5.0.

BUGS

     The current termcap(5) database does not define the 'ML' (set left soft margin) capability for any terminals.

BSD
								   May 20, 2002 							       BSD