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What does these two line in shell script mean ? What's the usage for &quot;[ ]&quot; and &quot;&amp;&amp;&quot;&nbsp;? <br />
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&nbsp; [ $RETVAL = 0 ] &amp;&amp;&nbsp;rm -f $lockfile<br />
&nbsp; return $RETVAL<br />
Tks
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What does these two line in shell script mean ? What's the usage for "[ ]" and "&&" ? 

  [ $RETVAL = 0 ] && rm -f $lockfile
  return $RETVAL
Tks

Shell script

The term 'shell' refers to a general class of text-based command interpreters most often associated with the UNIX and Linux operating systems. Popular shells include Bourne, Debian Almquist (dash), Korn (ksh), Bourne Again (bash) and the C shell family (csh). Some view the DOS 'cmd' prompt as a minimal shell of sorts. It is also possible to install Cygwin on Windows and emulate a full Unix environment with complete shell capabilities. Terminal emulators, such as xterm, GNOME Terminal and OS X Terminal, can be used to access shell.