php man page for shell_exec

SHELL_EXEC(3)								 1							     SHELL_EXEC(3)

shell_exec - Execute command via shell and return the complete output as a string

SYNOPSIS
       string shell_exec (string  $cmd)

DESCRIPTION
	This function is identical to the backtick operator.

PARAMETERS
	      o $cmd
		- The command that will be executed.

RETURN VALUES
	The output from the executed command or NULL if an error occurred or the command produces no output.

       Note

	       This  function  can return NULL both when an error occurs or the program produces no output. It is not possible to detect execution
	      failures using this function. exec(3) should be used when access to the program exit code is required.

EXAMPLES
       Example #1

	      A shell_exec(3) example

	      <?php
	      $output = shell_exec('ls -lart');
	      echo "<pre>$output</pre>";
	      ?>

NOTES
       Note

	       This function is disabled when PHP is running in safe mode.

SEE ALSO
       exec(3), escapeshellcmd(3).

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