3

I found on Centos4 that the man page for popen() states in part:

DESCRIPTION
   The  pclose()  function shall close a stream that was opened by popen(), wait for the command to termi-
   nate, and return the termination status of the process that was running  the  command  language  inter-
   preter.   However, if a call caused the termination status to be unavailable to pclose(), then pclose()
   shall return -1 with errno set to [ECHILD] to report this situation.

However, in my C++ application, when I actually execute the code, I see that the termination status is shifted left by 8 bits. Perhaps this is to distinguish a -1 from the pipe's termination status from pclose()'s own exit status of -1?

Is this portable behavior? Why doesn't the man page mention this? If not portable, which platforms conform to this behavior?

WilliamKF
  • 41,123
  • 68
  • 193
  • 295

2 Answers2

2

Just to add some code to shooper's answer above, you may want to do something on the lines of this:

#include <sys/wait.h>

//Get your exit code...
int status=pclose(pipe);

//...and ask how the process ended to clean up the exit code.
if(WIFEXITED(status)) {
    //If you need to do something when the pipe exited, this is the time.
    status=WEXITSTATUS(status);
}
else if(WIFSIGNALED(status)) {
    //If you need to add something if the pipe process was terminated, do it here.
    status=WTERMSIG(status);
}
else if(WIFSTOPPED(status)) {
    //If you need to act upon the process stopping, do it here.
    status=WSTOPSIG(status);
}

Other than that, add elegance as needed.

The Marlboro Man
  • 971
  • 7
  • 22
0

If you think about it, there is a "fork" in there, so you may want to "WIFEXITED" and "WEXITSTATUS".

From the man page:

The pclose() function waits for the associated process to terminate and returns the exit status of the command as returned by wait4(2).

shooper
  • 606
  • 4
  • 8