由于Web Server以及PHP的实现方式所限,我们在现实环境中很难利用PHP去调用一些Linux中需要root权限才能执行的程序,对此,我从网上找到另外一种方式来绕开这个限制。首先先写个c程序中转调用系统命令,然后用PHP去执行此c程序。
c程序
首先写个c文件,比如/usr/local/ismole/w.c
<ol class="dp-c"> <li class="alt"><span><span class="comment">//note 由于wordpress编辑器的原因,请将此代码中头文件多余的空格去除 </span> </span></li> <li><span><span class="preprocessor">#include </span> </span></li> <li class="alt"><span><span class="preprocessor">#include </span> </span></li> <li><span><span class="preprocessor">#include </span> </span></li> <li class="alt"><span><span class="preprocessor">#include </span><span> </span></span></li> <li><span> </span></li> <li class="alt"> <span class="keyword">int</span><span> main() </span> </li> <li><span>{ </span></li> <li class="alt"><span> uid_t uid ,euid; </span></li> <li><span> </span></li> <li class="alt"> <span> </span><span class="comment">//note 获得当前的uid </span><span> </span> </li> <li><span> uid = getuid(); </span></li> <li class="alt"> <span> </span><span class="comment">//note 获得当前euid </span><span> </span> </li> <li><span> euid = geteuid(); </span></li> <li class="alt"><span> </span></li> <li> <span> </span><span class="comment">//note 交换这两个id </span><span> </span> </li> <li class="alt"> <span> </span><span class="keyword">if</span><span>(setreuid(euid, uid)) </span> </li> <li> <span> perror(</span><span class="string">"setreuid"</span><span>); </span> </li> <li class="alt"><span> </span></li> <li> <span> </span><span class="comment">//note 执行将要执行linux系统命令 </span><span> </span> </li> <li class="alt"> <span> system(</span><span class="string">"/usr/bin/w"</span><span>); </span> </li> <li> <span> </span><span class="keyword">return</span><span> 0; </span> </li> <li class="alt"><span>} </span></li> </ol>
//note 由于wordpress编辑器的原因,请将此代码中头文件多余的空格去除
编译该文件gcc -o ipt -Wall w.c,这时会在当前目录下生成程序w。
改变此程序的属主chmod u+s ./w。
PHP执行
文件内容如下,放在web目录下,访问就会输出当前的服务器负载情况。
<ol class="dp-c"> <li class="alt"><span><span></span></span></li> <li> <span class="comment">//note key的验证过程 </span><span> </span> </li> <li class="alt"> <span class="keyword">if</span><span>(</span><span class="vars">$key</span><span> != </span><span class="vars">$authkey</span><span>) { </span> </li> <li> <span class="comment">// exit(key error); </span><span> </span> </li> <li class="alt"><span>} </span></li> <li><span> </span></li> <li class="alt"> <span class="vars">$last_line</span><span> = </span><span class="func">exec</span><span>(</span><span class="string">/usr/local/ismole/w</span><span>, </span><span class="vars">$retval</span><span>); </span> </li> <li><span> </span></li> <li class="alt"> <span class="vars">$returnArray</span><span> = </span><span class="func">explode</span><span>(</span><span class="string">"load average: "</span><span>, </span><span class="vars">$retval</span><span>[0]); </span> </li> <li> <span class="vars">$returnString</span><span> = </span><span class="vars">$returnArray</span><span>[1]; </span> </li> <li class="alt"><span> </span></li> <li> <span class="func">echo</span><span> </span><span class="vars">$returnString</span><span>; </span> </li> </ol>
按照上面的实例,我们可以用PHP来做任何我们想执行的Linux系统命令,SVN更新,服务器监控,备份,恢复,日常维护等等。比如《利用SVN搭建测试服务器》