php中使用exec,system等函數調用系統(tǒng)命令的方法(不建議使用,可導致安全問題)
Jun 13, 2016 am 11:58 AM
php的內置函數exec,system都可以調用系統(tǒng)命令(shell命令),當然還有passthru,escapeshellcmd等函數。
在很多時候利用php的exec,system等函數調用系統(tǒng)命令可以幫助我們更好更快的完成工作。比如前二天筆者在批量處理.rar文件時exec就幫我了大忙了。
今天整理一下常用的調用系統(tǒng)函數發(fā)出來和大家分享經驗。
注意:要想使用這二個函數php.ini中的安全模式必須關閉,要不然為了安全起見php是不讓調用系統(tǒng)命令的。
先看一下php手冊對這二個函數的解釋:
exec --- 執(zhí)行外部程式
語法 : string exec ( string command [, array &output [, int &return_var]] )
說明 :
exec( )執(zhí)行給予的命令command,不過它并不會輸出任何東西,它簡單的從命令的結果中傳回最后一行,如果你需要去執(zhí)行一個命令,并且從命令去取得所有資料時,可以使用passthru( )這個函數。
如果有給予參數array,則指定的數組將會被命令所輸出的每一行填滿,注意 : 如果數組先前已經包含了一些元素的話,exec( )將會把它附加在數組的后面,如果你不想要此函數附加元素的話,你可以在傳遞此數組給exec( )之前呼叫unset( )。
如果有給予參數array和return_var,則傳回執(zhí)行的狀態(tài)命令將會寫到這個變量。
注意 : 如果你允許來自使用者輸入的資料,可以傳遞到此函數,那么你應該使用escapeshellcmd( )來確定此使用者無法哄騙(trick)系統(tǒng)來執(zhí)行武斷的(arbitrary)命令。
注意 : 如果你使用此函數來啟動一個程式,而且希望在背景里(background)執(zhí)行的時候離開它,你必須確定此程式的輸出是轉向(redirected)到一個文件或是一些輸出的資料流,否則PHP將會懸掛(hang)直到程式執(zhí)行結束。
system --- 執(zhí)行外部程式并且顯示輸出
語法 : string system ( string command [, int &return_var] )
說明 :
system( )執(zhí)行給予的命令command,并且輸出結果。如果有給予參數return_var,則執(zhí)行命令的狀態(tài)碼將會寫到這個變量。
注意 : 如果你允許來自使用者輸入的資料,可以傳遞到此函數,那么你應該使用escapeshellcmd( )來確定此使用者無法哄騙(trick)系統(tǒng)來執(zhí)行武斷的(arbitrary)命令。
注意 : 如果你使用此函數來啟動一個程式,而且希望在背景里(background)執(zhí)行的時候離開它,你必須確定此程式的輸出是轉向(redirected)到一個文件或是一些輸出的資料流,否則PHP將會懸掛(hang)直到程式執(zhí)行結束。
如果PHP是運作成伺服器模組,在輸出每一行后,system( )會試著自動地清除web伺服器的輸出緩沖。
成功則傳回命令的最后一行,失敗則傳回false。
如果你需要去執(zhí)行一個命令,并且從命令去取得所有資料時,可以使用passthru( )這個函數。
這二個都是用來調用系統(tǒng)shell命令,
不同點:
exec可以把執(zhí)行的結果全部返回到$output函數里(數組),$status是執(zhí)行的狀態(tài) 0為成功 1為失敗
systerm不需要提供$output函數,他是直接把結果返回出來,同樣$return_var是執(zhí)行的狀態(tài)碼 0為成功 1為失敗
exec示例:
復制代碼 代碼如下:
$a = exec("dir",$out,$status);
print_r($a);
print_r($out);
print_r($status);
?>
system示例:
復制代碼 代碼如下:
$a = system("dir",$out);
print_r($a);
print_r($out);
?>
system、exce、passthru區(qū)別
system() 輸出并返回最后一行shell結果。
exec() 不輸出結果,返回最后一行shell結果,所有結果可以保存到一個返回的數組里面。
passthru() 只調用命令,把命令的運行結果原樣地直接輸出到標準輸出設備上。
相同點:都可以獲得命令執(zhí)行的狀態(tài)碼

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