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Full Discussion: Single UNIX command to display users and to count them
Top Forums UNIX for Dummies Questions & Answers Single UNIX command to display users and to count them Post 302739569 by sreyan32 on Tuesday 4th of December 2012 11:55:29 AM
Old 12-04-2012
Question
Quote:
Originally Posted by bakunin

Code:
$(( $(w| wc -l) - 2 ))

bakunin
Thank You so much for your detailed explanation. But I have some doubts-:

1) In the following code-:

Code:
$(( $(w| wc -l) - 2 ))

Why have you used two opening and two closing brackets for the outer expression and only one opening and one closing for the inner expression that is-:

Code:
$(w| wc -l)

I tried it with two opening and closing brackets for both inner and outer expression and I keep getting errors. Same thing if I try with one bracket for both inner and outer expressions.Why does it only work like the way that you have specified ?

2) When we use tee the stream is duplicated and by default the first stream is always printed out. Am I right in assuming this ? Or is there a way to control the output of both the divided streams?

3)The duplicate stream that tee creates is also an output stream. And we redirect that second duplicate stream to the following operations-:

Code:
(cut -d\  -f1|uniq | wc -l >/dev/stderr )

But then if there is already an output stream then why are we redirecting the output to the error stream ?

By the way do you know what the following command does-:

Code:
kill $!

I searched for it in Google but I did not get any such answer. I just don't want to open up another thread for only such a small topic. If you do know the answer then please let me know.

Thank You again for your explanation. It did help a lot.
 

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LEARN ABOUT SUSE

ansi_ctrlu

term::ansi::ctrl::unix(n)					 Terminal control					 term::ansi::ctrl::unix(n)

__________________________________________________________________________________________________________________________________________________

NAME

       term::ansi::ctrl::unix - Control operations and queries

SYNOPSIS

       package require Tcl  8.4

       package require term::ansi::ctrl::unix  ?0.1?

       ::term::ansi::ctrl::unix::import ?ns? ?arg...?

       ::term::ansi::ctrl::unix::raw

       ::term::ansi::ctrl::unix::raw

       ::term::ansi::ctrl::unix::columns

       ::term::ansi::ctrl::unix::rows

_________________________________________________________________

DESCRIPTION

       WARNING:  This  package	is  unix-specific  and depends on the availability of two unix system commands for terminal control, i.e. stty and
       tput, both of which have to be found in the $PATH. If any of these two commands is missing the loading of the package will fail.

       The package provides commands to switch the standard input of the current process between raw and cooked input modes, and to query the size
       of terminals, i.e. the available number of columns and lines.

API

   INTROSPECTION
       ::term::ansi::ctrl::unix::import ?ns? ?arg...?
	      This  command imports some or all attribute commands into the namespace ns. This is by default the namespace ctrl. Note that this is
	      relative namespace name, placing the imported command into a child of the current namespace. By default all commands  are  imported,
	      this can howver be restricted by listing the names of the wanted commands after the namespace argument.

   OPERATIONS
       ::term::ansi::ctrl::unix::raw
	      This command switches the standard input of the current process to raw input mode. This means that from then on all characters typed
	      by the user are immediately reported to the application instead of waiting in the OS buffer until the Enter/Return key is received.

       ::term::ansi::ctrl::unix::raw
	      This command switches the standard input of the current process to cooked input mode. This means that from then  on  all	characters
	      typed by the user are kept in OS buffers for editing until the Enter/Return key is received.

       ::term::ansi::ctrl::unix::columns
	      This command queries the terminal connected to the standard input for the number of columns available for display.

       ::term::ansi::ctrl::unix::rows
	      This command queries the terminal connected to the standard input for the number of rows (aka lines) available for display.

BUGS, IDEAS, FEEDBACK
       This  document, and the package it describes, will undoubtedly contain bugs and other problems.	Please report such in the category term of
       the Tcllib SF Trackers [http://sourceforge.net/tracker/?group_id=12883].  Please also report any ideas for enhancements you  may  have  for
       either package and/or documentation.

KEYWORDS

       ansi, columns, control, cooked, input mode, lines, raw, rows, terminal

COPYRIGHT

       Copyright (c) 2006 Andreas Kupries <andreas_kupries@users.sourceforge.net>

term									0.1						 term::ansi::ctrl::unix(n)
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