exec
If the output argument is present, then the specified array will be filled with every line of output from the command. Trailing whitespace, such as \n , is 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 result_code argument is present along with the output argument, then the return status of the executed command will be written to this variable.
Return Values
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.
Returns false on failure.
To get the output of the executed command, be sure to set and use the output parameter.
Errors/Exceptions
Emits an E_WARNING if exec() is unable to execute the command .
Throws a ValueError if command is empty or contains null bytes.
Changelog
| Version | Description |
|---|---|
| 8.0.0 | If command is empty or contains null bytes, exec() now throws a ValueError . Previously it emitted an E_WARNING and returned false . |
Examples
Example #1 An exec() example
// outputs the username that owns the running php/httpd process
// (on a system with the «whoami» executable in the path)
$output = null ;
$retval = null ;
exec ( ‘whoami’ , $output , $retval );
echo «Returned with status $retval and output:\n» ;
print_r ( $output );
?>
The above example will output something similar to:
Returned with status 0 and output: Array ( [0] => cmb )
Notes
When allowing user-supplied data to be passed to this function, use escapeshellarg() or escapeshellcmd() to ensure that users cannot trick the system into executing arbitrary commands.
Note:
If a program is started with this function, in order for it to continue running in the background, the output of the program must be redirected to a file or another output stream. Failing to do so will cause PHP to hang until the execution of the program ends.
Note:
On Windows exec() will first start cmd.exe to launch the command. If you want to start an external program without starting cmd.exe use proc_open() with the bypass_shell option set.
See Also
- system() — Execute an external program and display the output
- passthru() — Execute an external program and display raw output
- escapeshellcmd() — Escape shell metacharacters
- pcntl_exec() — Executes specified program in current process space
- backtick operator
User Contributed Notes 20 notes
This will execute $cmd in the background (no cmd window) without PHP waiting for it to finish, on both Windows and Unix.
function execInBackground ( $cmd ) <
if ( substr ( php_uname (), 0 , 7 ) == «Windows» ) <
pclose ( popen ( «start /B » . $cmd , «r» ));
>
else <
exec ( $cmd . » > /dev/null &» );
>
>
?>
(This is for linux users only).
We know now how we can fork a process in linux with the & operator.
And by using command: nohup MY_COMMAND > /dev/null 2>&1 & echo $! we can return the pid of the process.
This small class is made so you can keep in track of your created processes ( meaning start/stop/status ).
You may use it to start a process or join an exisiting PID process.
// You may use status(), start(), and stop(). notice that start() method gets called automatically one time.
$process = new Process ( ‘ls -al’ );
// or if you got the pid, however here only the status() metod will work.
$process = new Process ();
$process . setPid ( my_pid );
?>
// Then you can start/stop/ check status of the job.
$process . stop ();
$process . start ();
if ( $process . status ()) echo «The process is currently running» ;
>else echo «The process is not running.» ;
>
?>
/* An easy way to keep in track of external processes.
* Ever wanted to execute a process in php, but you still wanted to have somewhat controll of the process ? Well.. This is a way of doing it.
* @compability: Linux only. (Windows does not work).
* @author: Peec
*/
class Process private $pid ;
private $command ;
public function __construct ( $cl = false ) if ( $cl != false ) $this -> command = $cl ;
$this -> runCom ();
>
>
private function runCom () $command = ‘nohup ‘ . $this -> command . ‘ > /dev/null 2>&1 & echo $!’ ;
exec ( $command , $op );
$this -> pid = (int) $op [ 0 ];
>
public function setPid ( $pid ) $this -> pid = $pid ;
>
public function getPid () return $this -> pid ;
>
public function status () $command = ‘ps -p ‘ . $this -> pid ;
exec ( $command , $op );
if (!isset( $op [ 1 ]))return false ;
else return true ;
>
public function start () if ( $this -> command != » ) $this -> runCom ();
else return true ;
>
public function stop () $command = ‘kill ‘ . $this -> pid ;
exec ( $command );
if ( $this -> status () == false )return true ;
else return false ;
>
>
?>
Calling command line from php
- Tell PHP to execute a certain file.
$ php my_script.php $ php -f my_script.php
$ php -r 'print_r(get_defined_constants());'
Note: Read the example carefully: there are no beginning or ending tags! The -r switch simply does not need them, and using them will lead to a parse error.
$ some_application | some_filter | php | sort -u > final_output.txt
As with every shell application, the PHP binary accepts a number of arguments; however, the PHP script can also receive further arguments. The number of arguments that can be passed to your script is not limited by PHP (and although the shell has a limit to the number of characters which can be passed, this is not in general likely to be hit). The arguments passed to the script are available in the global array $argv . The first index (zero) always contains the name of the script as called from the command line. Note that, if the code is executed in-line using the command line switch -r, the value of $argv[0] will be «Standard input code» ; prior to PHP 7.2.0, it was a dash ( «-» ) instead. The same is true if the code is executed via a pipe from STDIN .
A second global variable, $argc , contains the number of elements in the $argv array (not the number of arguments passed to the script).
As long as the arguments to be passed to the script do not start with the — character, there’s nothing special to watch out for. Passing an argument to the script which starts with a — will cause trouble because the PHP interpreter thinks it has to handle it itself, even before executing the script. To prevent this, use the argument list separator — . After this separator has been parsed by PHP, every following argument is passed untouched to the script.
# This will not execute the given code but will show the PHP usage $ php -r 'var_dump($argv);' -h Usage: php [options] [-f] [args. ] [. ] # This will pass the '-h' argument to the script and prevent PHP from showing its usage $ php -r 'var_dump($argv);' -- -h array(2) < [0]=>string(1) "-" [1]=> string(2) "-h" >
However, on Unix systems there’s another way of using PHP for shell scripting: make the first line of the script start with #!/usr/bin/php (or whatever the path to your PHP CLI binary is if different). The rest of the file should contain normal PHP code within the usual PHP starting and end tags. Once the execution attributes of the file are set appropriately (e.g. chmod +x test), the script can be executed like any other shell or perl script:
Example #1 Execute PHP script as shell script
Assuming this file is named test in the current directory, it is now possible to do the following:
$ chmod +x test $ ./test -h -- foo array(4) < [0]=>string(6) "./test" [1]=> string(2) "-h" [2]=> string(2) "--" [3]=> string(3) "foo" >
As can be seen, in this case no special care needs to be taken when passing parameters starting with — .
The PHP executable can be used to run PHP scripts absolutely independent of the web server. On Unix systems, the special #! (or «shebang») first line should be added to PHP scripts so that the system can automatically tell which program should run the script. On Windows platforms, it’s possible to associate php.exe with the double click option of the .php extension, or a batch file can be created to run scripts through PHP. The special shebang first line for Unix does no harm on Windows (as it’s formatted as a PHP comment), so cross platform programs can be written by including it. A simple example of writing a command line PHP program is shown below.
Example #2 Script intended to be run from command line (script.php)
if ( $argc != 2 || in_array ( $argv [ 1 ], array( ‘—help’ , ‘-help’ , ‘-h’ , ‘-?’ ))) ?>
This is a command line PHP script with one option.
can be some word you would like
to print out. With the —help, -help, -h,
or -? options, you can get this help.
The script above includes the Unix shebang first line to indicate that this file should be run by PHP. We are working with a CLI version here, so no HTTP headers will be output.
The program first checks that there is the required one argument (in addition to the script name, which is also counted). If not, or if the argument was —help, -help, -h or -?, the help message is printed out, using $argv[0] to dynamically print the script name as typed on the command line. Otherwise, the argument is echoed out exactly as received.
To run the above script on Unix, it must be made executable, and called simply as script.php echothis or script.php -h. On Windows, a batch file similar to the following can be created for this task:
Example #3 Batch file to run a command line PHP script (script.bat)
@echo OFF "C:\php\php.exe" script.php %*
Assuming the above program is named script.php , and the CLI php.exe is in C:\php\php.exe , this batch file will run it, passing on all appended options: script.bat echothis or script.bat -h.
See also the Readline extension documentation for more functions which can be used to enhance command line applications in PHP.
On Windows, PHP can be configured to run without the need to supply the C:\php\php.exe or the .php extension, as described in Command Line PHP on Microsoft Windows.
Note:
On Windows it is recommended to run PHP under an actual user account. When running under a network service certain operations will fail, because «No mapping between account names and security IDs was done».
User Contributed Notes 7 notes
On Linux, the shebang (#!) line is parsed by the kernel into at most two parts.
For example:
1: #!/usr/bin/php
2: #!/usr/bin/env php
3: #!/usr/bin/php -n
4: #!/usr/bin/php -ddisplay_errors=E_ALL
5: #!/usr/bin/php -n -ddisplay_errors=E_ALL
1. is the standard way to start a script. (compare «#!/bin/bash».)
2. uses «env» to find where PHP is installed: it might be elsewhere in the $PATH, such as /usr/local/bin.
3. if you don’t need to use env, you can pass ONE parameter here. For example, to ignore the system’s PHP.ini, and go with the defaults, use «-n». (See «man php».)
4. or, you can set exactly one configuration variable. I recommend this one, because display_errors actually takes effect if it is set here. Otherwise, the only place you can enable it is system-wide in php.ini. If you try to use ini_set() in your script itself, it’s too late: if your script has a parse error, it will silently die.
5. This will not (as of 2013) work on Linux. It acts as if the whole string, «-n -ddisplay_errors=E_ALL» were a single argument. But in BSD, the shebang line can take more than 2 arguments, and so it may work as intended.
Summary: use (2) for maximum portability, and (4) for maximum debugging.