title: C/C++ linux fork() and exec()
body: <p>I'm use fork() to create child process. From child process I am use exec() to launch new process. My code as below:</p>
  
  <pre><code>   ......
     pid = fork();
     if (pid &gt; 0) {
         WriteLog("Parent Process");
         //Do something
     } else if (pid == 0) {
         WriteLog("Child process");
         int return = execl(ShellScript);
         if ( return == -1 ) 
            WriteLog("Launch process fail");
     } else {
         WriteLog("Can't create child process");
     }
     ......
  </code></pre>
  
  <p>Note: WriteLog function will be open file, write log, and close file. (It is flushed)
        ShellScript will launch new process c/c++.</p>
  
  <p>I run  my program for long run and the code above is called many times. And sometime (rarely) there are problem happen that the new process can't launch successful although the child process is created successfully (I have checked carefully). And one thing is extremely misunderstand when this problem happen that the "Child process" log can't printed although the child process is created successful.</p>
  
  <p>In normal case (there are not error happen) the number of times print the "Child process" and "Parent process" log are the same.</p>
  
  <p>In abnormal case, they are not the same although the child process always create successfully.The "Launch process fail" and "Can't create child process" log aren't printed in this case.
  Please help me for consult.</p>