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POExecuting commands with pipes and timeout in c++ (and reading stdout)
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  1. POExecuting commands with pipes and timeout in c++ (and reading stdout)
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    copied!<p>I need your help !</p> <p>I made a reporting deamon (in c++) which needs to periodicaly execute a bunch of commands on a server.</p> <p>A simple example command would be : "/bin/ps aux | /usr/bin/wc -l"</p> <p>The first idea was to fork a child process that runs the command with popen() and set up an alarm() in the parent process to kill the child after 5 seconds if the command has not exited already.</p> <p>I tried using "sleep 20000" as command, the child process is killed but the sleep command is still running... not good.</p> <p>The second idea was to use execlp() instead of popen(), it works with simple commands (ie with no pipes) such as "ls -lisa" or "sleep 20000". I can get the result and the processes are killed if they're not done after 5 seconds.</p> <p>Now I need to execute that "/bin/ps aux | /usr/bin/wc -l" command, obviously it won't work with execlp() directly, so I tried that "hack" : </p> <pre><code>execlp("sh","sh","-c","/bin/ps aux | /usr/bin/wc -l",NULL); </code></pre> <p>I works... or so I thought... I tried </p> <pre><code>execlp("sh","sh","-c","sleep 20000",NULL); </code></pre> <p>just to be sure and the child process is killed after 5 secs (my timeout) but the sleep command just stays there...</p> <p>i'm open for suggestions (I'd settle for a hack) !</p> <p>Thanks in advance !</p> <p>TLDR; </p> <p>I need a way to :</p> <ul> <li>execute a "complex" command such as "/bin/ps aux | /usr/bin/wc -l" </li> <li>get its output</li> <li>make sure it's killed if it takes more than 5 seconds (the ps command is just and example, actual commands may hang forever)</li> </ul>
 

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