exec
Execute an external program
Description
string exec
( string $command
[, array &$output
[, int &$return_var
]] )
Parameters
-
command
-
The command that will be executed.
-
output
-
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.
-
return_var
-
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.
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.
To get the output of the executed command, be sure to set and use the
output parameter.
Examples
Example #1 An exec example
<?php
// outputs the username that owns the running php/httpd process
// (on a system with the "whoami" executable in the path)
echo exec('whoami');
?>
Notes
WarningWhen 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.
Note: When
safe mode is enabled, you can only
execute files within the safe_mode_exec_dir.
For practical reasons, it is currently not allowed to have ..
components in the path to the executable.
WarningWith safe mode enabled,
the command string is escaped with escapeshellcmd. Thus,
echo y | echo x becomes echo y \| echo x.