system
(PHP 4, PHP 5)
system — Execute an external program and display the output
說明
system() is just like the C version of the function in that it executes the given command and outputs the result.
The system() call also tries to automatically flush the web server's output buffer after each line of output if PHP is running as a server module.
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.
參數
- command
-
The command that will be executed.
- return_var
-
If the return_var argument is present, then the return status of the executed command will be written to this variable.
Return值
Returns the last line of the command output on success, and FALSE on failure.
範例
Example#1 system() example
<?php
echo '<pre>';
// Outputs all the result of shellcommand "ls", and returns
// the last output line into $last_line. Stores the return value
// of the shell command in $retval.
$last_line = system('ls', $retval);
// Printing additional info
echo '
</pre>
<hr />Last line of the output: ' . $last_line . '
<hr />Return value: ' . $retval;
?>
註釋
如果想允許使用者輸入的資料傳入本函式，則應使用 escapeshellarg() 或 escapeshellcmd() 函式來確保用戶不能欺騙系統從而執行任意命令。
Note: 如果用本函式啟動一個程序並希望保持在背景執行，必須確保該程序的輸出被導向到一個檔案或其它輸出流，否則 PHP 會在等待程序執行結束。
Note: 在啟用了安全模式時，只能執行在 safe_mode_exec_dir 之內的執行檔。為實用起見目前不能在執行檔的路徑中包含 .. 元素。
在啟用了安全模式時，命令字串會被 escapeshellcmd() 跳脫。所以 echo y | echo x 就成了 echo "y | echo x"。