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.
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');
?>
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.
Note: When safe mode is enabled, you can only execute executables
within the safe_mode_exec_dir. For practical reasons it
is currently not allowed to have .. components in the path
to the executable.
Warning
With safe mode enabled, all words following the initial
command string are treated as a single argument. Thus, echo
y | echo x becomes echo "y | echo x".
See also system(), passthru(), popen(), escapeshellcmd(),
and the backtick operator.
