Question on NULL and zero value of variable

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LEARN ABOUT CENTOS

string::shellquote

ShellQuote(3)						User Contributed Perl Documentation					     ShellQuote(3)

NAME

       String::ShellQuote - quote strings for passing through the shell

SYNOPSIS

	   $string = shell_quote @list;
	   $string = shell_quote_best_effort @list;
	   $string = shell_comment_quote $string;

DESCRIPTION

       This module contains some functions which are useful for quoting strings which are going to pass through the shell or a shell-like object.

       shell_quote [string]...
	   shell_quote quotes strings so they can be passed through the shell.	Each string is quoted so that the shell will pass it along as a
	   single argument and without further interpretation.	If no strings are given an empty string is returned.

	   If any string can't be safely quoted shell_quote will croak.

       shell_quote_best_effort [string]...
	   This is like shell_quote, excpet if the string can't be safely quoted it does the best it can and returns the result, instead of dying.

       shell_comment_quote [string]
	   shell_comment_quote quotes the string so that it can safely be included in a shell-style comment (the current algorithm is that a sharp
	   character is placed after any newlines in the string).

	   This routine might be changed to accept multiple string arguments in the future.  I haven't done this yet because I'm not sure if the
	   strings should be joined with blanks ($") or nothing ($,).  Cast your vote today!  Be sure to justify your answer.

EXAMPLES

	   $cmd = 'fuser 2>/dev/null ' . shell_quote @files;
	   @pids = split ' ', `$cmd`;

	   print CFG "# Configured by: ",
		       shell_comment_quote($ENV{LOGNAME}), "
";

BUGS

       Only Bourne shell quoting is supported.	I'd like to add other shells (particularly cmd.exe), but I'm not familiar with them.  It would be
       a big help if somebody supplied the details.

AUTHOR

       Roderick Schertler <roderick@argon.org>

SEE ALSO

       perl(1).

perl v5.16.3							    2010-06-11							     ShellQuote(3)

Shell Programming and Scripting