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Full Discussion: Understanding ampersand (&) usage in the command
Top Forums Shell Programming and Scripting Understanding ampersand (&) usage in the command Post 302422338 by zaxxon on Tuesday 18th of May 2010 06:33:10 AM
Old 05-18-2010
You are right but I guess that this is just a typo and missing a 2nd adjacent & like marked bold here:
Code:
who && echo "Total number of users are `who|wc -l`"

This works then like if the 1st who is successful, the command following will be executed, maybe to check if "who" itself is available and working. Sending "who" in the background and then following up the rest of commands would make no sense.
 

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LEARN ABOUT DEBIAN

ansi_cattr

term::ansi::code::attr(3tcl)					 Terminal control				      term::ansi::code::attr(3tcl)

__________________________________________________________________________________________________________________________________________________

NAME

       term::ansi::code::attr - ANSI attribute sequences

SYNOPSIS

       package require Tcl  8.4

       package require term::ansi::code  ?0.1?

       package require term::ansi::code::attr  ?0.1?

       ::term::ansi::code::attr::names

       ::term::ansi::code::attr::import ?ns? ?arg...?

       ::term::ansi::code::attr::fgblack

       ::term::ansi::code::attr::fgred

       ::term::ansi::code::attr::fggreen

       ::term::ansi::code::attr::fgyellow

       ::term::ansi::code::attr::fgblue

       ::term::ansi::code::attr::fgmagenta

       ::term::ansi::code::attr::fgcyan

       ::term::ansi::code::attr::fgwhite

       ::term::ansi::code::attr::fgdefault

       ::term::ansi::code::attr::bgblack

       ::term::ansi::code::attr::bgred

       ::term::ansi::code::attr::bggreen

       ::term::ansi::code::attr::bgyellow

       ::term::ansi::code::attr::bgblue

       ::term::ansi::code::attr::bgmagenta

       ::term::ansi::code::attr::bgcyan

       ::term::ansi::code::attr::bgwhite

       ::term::ansi::code::attr::bgdefault

       ::term::ansi::code::attr::bold

       ::term::ansi::code::attr::dim

       ::term::ansi::code::attr::italic

       ::term::ansi::code::attr::underline

       ::term::ansi::code::attr::blink

       ::term::ansi::code::attr::revers

       ::term::ansi::code::attr::hidden

       ::term::ansi::code::attr::strike

       ::term::ansi::code::attr::nobold

       ::term::ansi::code::attr::noitalic

       ::term::ansi::code::attr::nounderline

       ::term::ansi::code::attr::noblink

       ::term::ansi::code::attr::norevers

       ::term::ansi::code::attr::nohidden

       ::term::ansi::code::attr::nostrike

       ::term::ansi::code::attr::reset

_________________________________________________________________

DESCRIPTION

       This package provides symbolic names for the ANSI attribute control codes. For each control code a single command is provided which returns
       this code as its result. None of the commands of this package write  to	a  channel;  that  is  handled	by  higher  level  packages,  like
       term::ansi::send.

API

   INTROSPECTION
       ::term::ansi::code::attr::names
	      This command is for introspection. It returns as its result a list containing the names of all attribute commands.

       ::term::ansi::code::attr::import ?ns? ?arg...?
	      This  command imports some or all attribute commands into the namespace ns. This is by default the namespace attr. 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.

   ATTRIBUTES
       ::term::ansi::code::attr::fgblack
	      Set text color to Black.

       ::term::ansi::code::attr::fgred
	      Set text color to Red.

       ::term::ansi::code::attr::fggreen
	      Set text color to Green.

       ::term::ansi::code::attr::fgyellow
	      Set text color to Yellow.

       ::term::ansi::code::attr::fgblue
	      Set text color to Blue.

       ::term::ansi::code::attr::fgmagenta
	      Set text color to Magenta.

       ::term::ansi::code::attr::fgcyan
	      Set text color to Cyan.

       ::term::ansi::code::attr::fgwhite
	      Set text color to White.

       ::term::ansi::code::attr::fgdefault
	      Set default text color (Black).

       ::term::ansi::code::attr::bgblack
	      Set background to Black.

       ::term::ansi::code::attr::bgred
	      Set background to Red.

       ::term::ansi::code::attr::bggreen
	      Set background to Green.

       ::term::ansi::code::attr::bgyellow
	      Set background to Yellow.

       ::term::ansi::code::attr::bgblue
	      Set background to Blue.

       ::term::ansi::code::attr::bgmagenta
	      Set background to Magenta.

       ::term::ansi::code::attr::bgcyan
	      Set background to Cyan.

       ::term::ansi::code::attr::bgwhite
	      Set background to White.

       ::term::ansi::code::attr::bgdefault
	      Set default background (Transparent).

       ::term::ansi::code::attr::bold
	      Bold on.

       ::term::ansi::code::attr::dim
	      Dim on.

       ::term::ansi::code::attr::italic
	      Italics on.

       ::term::ansi::code::attr::underline
	      Underscore on.

       ::term::ansi::code::attr::blink
	      Blink on.

       ::term::ansi::code::attr::revers
	      Reverse on.

       ::term::ansi::code::attr::hidden
	      Hidden on.

       ::term::ansi::code::attr::strike
	      Strike-through on.

       ::term::ansi::code::attr::nobold
	      Bold off.

       ::term::ansi::code::attr::noitalic
	      Italics off.

       ::term::ansi::code::attr::nounderline
	      Underscore off.

       ::term::ansi::code::attr::noblink
	      Blink off.

       ::term::ansi::code::attr::norevers
	      Reverse off.

       ::term::ansi::code::attr::nohidden
	      Hidden off.

       ::term::ansi::code::attr::nostrike
	      Strike-through off.

       ::term::ansi::code::attr::reset
	      Reset all attributes to their default values.

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, attribute control, color control, control, terminal

CATEGORY

       Terminal control

COPYRIGHT

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

term									0.1					      term::ansi::code::attr(3tcl)
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