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The usage scenarios of the four PHP functions shell_exec, exec, passthru, and system

不言
不言Original
2018-05-03 09:36:303273browse

This article mainly introduces the usage scenarios of the four PHP functions shell_exec, exec, passthru, and system. It has certain reference value. Now I share it with everyone. Friends in need can refer to it


#You can execute related commands of the operating system. I feel that one application scenario is to start another process in the background to execute some time-consuming content without displaying the results in the front desk. It is a bit Similar to scheduled tasks, it can also replace queues in simple scenarios. For example, there is a file abc.php, which contains information related to sending emails, which is relatively time-consuming. In other files, after processing the normal logic, I want to send an email, but I don’t want to care whether the email is successful or not. As long as it is executed, that’s it:

//正常逻辑
...
//处理费时的
exec('php abc.php  > /dev/null &');
// 或者
exec('php abc.php | at now');
//继续走你
...

Similar to this, the above is only for Linux, There may be permission issues or path issues, and Windows may need other functions to handle it.

Detailed explanation of how exec, system and other functions in PHP call system commands

PHP’s built-in functions exec and system can all call system commands (shell command), of course, there are also passthru, escapeshellcmd and other functions.


In many cases, using PHP’s exec, system and other functions to call system commands can help us complete our work better and faster. For example, exec helped me a lot when I was batch processing .rar files two days ago.

Today I will sort out the commonly used calling system functions and share my experience with everyone.

Note: If you want to use these two functions, the safe mode in php.ini must be turned off, otherwise PHP will not be allowed to call system commands for security reasons.

First, let’s take a look at the explanation of these two functions in the PHP manual:

exec --- Execute external programs

Syntax: string exec ( string command [, array &output [ , int &return_var]] )

 exec function analysis

 exec syntax: string exec(string command , string [array], int [return_var]);

 exec return value: String

 Exec parameter description

 Command – the command to be executed

 Array – is the output value

 return_var – is the return value 0 or 1. If 0 is returned, the execution is successful, and if 1 is returned, the execution fails.

 exec failed, debugging plan

  一个技巧就是使用管道命令, 使用 2>&1, 命令就会输出shell执行时的错误到$output变量, 输出该变量即可分析。

  如:

  exec('convert a.jpg b.jpg', $output, $return_val);

  改为:

  exec('convert a.jpg b.jpg 2>&1', $output, $return_val);

  print_r($output);

  说明 :

  exec( )执行给予的命令command,不过它并不会输出任何东西,它简单的从命令的结果中传回最后一行,如果你需要去执行一个命令,并且从命令去取得所有资料时,可以使用passthru( )这个函数。

  如果有给予参数array,则指定的数组将会被命令所输出的每一行填满,注意 : 如果数组先前已经包含了一些元素的话,exec( )将会把它附加在数组的后面,如果你不想要此函数附加元素的话,你可以在传递此数组给exec( )之前呼叫unset( )。

  如果有给予参数array和return_var,则传回执行的状态命令将会写到这个变量。

  注意 : 如果你允许来自使用者输入的资料,可以传递到此函数,那么你应该使用escapeshellcmd( )来确定此使用者无法哄骗(trick)系统来执行武断的(arbitrary)命令。

  注意 : 如果你使用此函数来启动一个程式,而且希望在背景里(background)执行的时候离开它,你必须确定此程式的输出是转向(redirected)到一个文件或是一些输出的资料流,否则PHP将会悬挂(hang)直到程式执行结束。

  system --- 执行外部程式并且显示输出

  语法 : string system ( string command [, int &return_var] )

  说明 :

  system( )执行给予的命令command,并且输出结果。如果有给予参数return_var,则执行命令的状态码将会写到这个变量。

  注意 : 如果你允许来自使用者输入的资料,可以传递到此函数,那么你应该使用escapeshellcmd( )来确定此使用者无法哄骗(trick)系统来执行武断的(arbitrary)命令。

  注意 : 如果你使用此函数来启动一个程式,而且希望在背景里(background)执行的时候离开它,你必须确定此程式的输出是转向(redirected)到一个文件或是一些输出的资料流,否则PHP将会悬挂(hang)直到程式执行结束。

  如果PHP是运作成伺服器模组,在输出每一行后,system( )会试着自动地清除web伺服器的输出缓冲。

  成功则传回命令的最后一行,失败则传回false。

  如果你需要去执行一个命令,并且从命令去取得所有资料时,可以使用passthru( )这个函数。

  这二个都是用来调用系统shell命令,

  不同点:

  exec可以把执行的结果全部返回到$output函数里(数组),$status是执行的状态 0为成功 1为失败

  systerm不需要提供$output函数,他是直接把结果返回出来,同样$return_var是执行的状态码 0为成功 1为失败

    exec示例:

  <?php  
        $a = exec("dir",$out,$status);  
        print_r($a);  
        print_r($out);  
        print_r($status);  
    ?>
<code class="hljs bash" style="padding:10px;background-color:rgb(63,63,63);color:rgb(220,220,220);font-size:13px;line-height:1.4;font-family:Menlo, Monaco, Consolas, &#39;Courier New&#39;, monospace;"><?php    
    <span class="hljs-variable" style="color:rgb(239,220,188);">$a</span> = <span class="hljs-built_in" style="color:rgb(204,147,147);">exec</span>(<span class="hljs-string" style="color:rgb(204,147,147);">"dir"</span>,<span class="hljs-variable" style="color:rgb(239,220,188);">$out</span>,<span class="hljs-variable" style="color:rgb(239,220,188);">$status</span>);    
    <span class="hljs-built_in" style="color:rgb(204,147,147);">print</span>_r(<span class="hljs-variable" style="color:rgb(239,220,188);">$a</span>);    
    <span class="hljs-built_in" style="color:rgb(204,147,147);">echo</span> <span class="hljs-string" style="color:rgb(204,147,147);">"<br>-----------------------------------------------------<br>"</span>;  
    <span class="hljs-built_in" style="color:rgb(204,147,147);">echo</span> <span class="hljs-string" style="color:rgb(204,147,147);">"<pre class="brush:php;toolbar:false">"</span>;  
    //<span class="hljs-built_in" style="color:rgb(204,147,147);">print</span>_r(<span class="hljs-variable" style="color:rgb(239,220,188);">$out</span>);   
    var_dump(<span class="hljs-variable" style="color:rgb(239,220,188);">$out</span>);  
    <span class="hljs-built_in" style="color:rgb(204,147,147);">echo</span> <span class="hljs-string" style="color:rgb(204,147,147);">"
"; echo "
-----------------------------------------------------
"
; print_r($status); ?>

    system示例:

    <?php  
        $a = system("dir",$out);  
        print_r($a);  
        print_r($out);  
    ?>
<code class="hljs xml" style="padding:10px;background-color:rgb(63,63,63);color:rgb(220,220,220);
font-size:13px;
line-height:1.4;
font-family:Menlo, Monaco, Consolas, &#39;Courier New&#39;, monospace;"><span class="php"><span class="hljs-meta" style="color:rgb(127,159,127);"><span class="php"><span class="hljs-meta"><?php</span></span></span><span class="php">   
    $a = system(</span><span class="hljs-string" style="color:rgb(204,147,147);"><span class="php"><span class="hljs-string" style="color:rgb(204,147,147);">"dir"</span></span></span><span class="php">,$out);   
    </span><span class="hljs-keyword" style="color:rgb(227,206,171);"><span class="php"><span class="hljs-keyword" style="color:rgb(227,206,171);">echo</span></span></span><span class="php"> </span><span class="hljs-string" style="color:rgb(204,147,147);"><span class="php"><span class="hljs-string" style="color:rgb(204,147,147);">"<pre class="brush:php;toolbar:false">"</span></span></span><span class="php">;  
    </span><span class="hljs-comment" style="color:rgb(127,159,127);"><span class="php"><span class="hljs-comment" style="color:rgb(127,159,127);">//print_r($a); </span></span></span><span class="php">  
    var_dump($a);  
    </span><span class="hljs-keyword" style="color:rgb(227,206,171);"><span class="php"><span class="hljs-keyword" style="color:rgb(227,206,171);">echo</span></span></span><span class="php"> </span><span class="hljs-string" style="color:rgb(204,147,147);"><span class="php"><span class="hljs-string" style="color:rgb(204,147,147);">"
"; echo "
-----------------------------------------------------
"
; print_r($out); ?>

 大家可以运行一下看效果 

PHP执行系统外部命令:exec()、passthru()、system()、shell_exec()

在php开发网站中,经常需要执行系统外部命令。php提供4种方法执行系统外部命令:exec()、passthru()、system()、 shell_exec()。下面一一介绍。在开始前,先检查下php配置文件php.ini中是有禁止这是个函数。找到 disable_functions,配置如下:

disable_functions =

如果“disable_functions=”后面有接上面四个函数,将其删除。默认php.ini配置文件中是不禁止你调用执行外部命令的函数的。

方法一:exec()

function exec(string $command,array[optional] $output,int[optional] $return_value)

php代码:

<?php
        echo exec("ls",$file);
        echo "</br>";
        print_r($file);
?>

执行结果:

test.php
Array( [0] => index.php [1] => test.php)

知识点:

exec 执行系统外部命令时不会输出结果,而是返回结果的最后一行,如果你想得到结果你可以使用第二个参数,让其输出到指定的数组,此数组一个记录代表输出的一 行,即如果输出结果有20行,则这个数组就有20条记录,所以如果你需要反复输出调用不同系统外部命令的结果,你最好在输出每一条系统外部命令结果时清空 这个数组,以防混乱。第三个参数用来取得命令执行的状态码,通常执行成功都是返回0。

 

方法二:passthru()

function passthru(string $command,int[optional] $return_value)

代码:

<?php
        passthru("ls");
?>

执行结果:

index.phptest.php

知识点:

passthru与system的区别,passthru直接将结果输出到浏览器,不需要使用 echo 或 return 来查看结果,不返回任何值,且其可以输出二进制,比如图像数据。

 

方法三:system()

function system(string $command,int[optional] $return_value)

代码:

<?php
        system("ls /");
?>

执行结果:

binbootcgroupdevetchomeliblost+foundmediamntoptprocrootsbinselinuxsrvsystmpusrvar

知识点:

system和exec的区别在于system在执行系统外部命令时,直接将结果输出到游览器,不需要使用 echo 或 return 来查看结果,如果执行命令成功则返回true,否则返回false。第二个参数与exec第三个参数含义一样。

 

方法四:反撇号`和shell_exec()

shell_exec() 函数实际上仅是反撇号 (`) 操作符的变体

代码:

<?php
        echo `pwd`;
?>

执行结果:

/var/www/html

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