   #PHP Manual Program Execution functions escapeshellcmd passthru

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                                     exec

   (PHP 3, PHP 4 )
   exec -- Execute an external program

Description

   string exec ( string command [, array output [, int return_var]])

   exec() executes the given command, however it does not output
   anything. It simply returns the last line from the result of the
   command. If you need to execute a command and have all the data from
   the command passed directly back without any interference, use the
   passthru() function.

   If the output argument is present, then the specified array will be
   filled with every line of output from the command. Line endings, such
   as \n, are not included in this array. Note that if the array already
   contains some elements, exec() will append to the end of the array. If
   you do not want the function to append elements, call unset() on the
   array before passing it to exec().

   If the return_var argument is present along with the output argument,
   then the return status of the executed command will be written to this
   variable.

   Warning

   If you are going to allow data coming from user input to be passed to
   this function, then you should be using escapeshellarg() or
   escapeshellcmd() to make sure that users cannot trick the system into
   executing arbitrary commands.

     Note: If you start a program using this function and want to leave
     it running in the background, you have to make sure that the output
     of that program is redirected to a file or some other output stream
     or else PHP will hang until the execution of the program ends.

   See also system(), passthru(), popen(), escapeshellcmd(), and the
   backtick operator.
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