LinuxQuestions.org - X Error with system()/fork()

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X Error with system()/fork()

While running my 'execute' ( execute("echo hi") ) function, I get this error:

Quote:

hi
Xlib: unexpected async reply (sequence 0x2d8)!

system() by itself works without the error, but I want the 'execute' function to run a command and not hang the gui waiting for it to finish.

The execute function:

Code:

void execute(const char *cmd)

{

  switch(fork())

  {

    case -1:

      perror("execute: fork");

      return;

    case 0:

      if (system(cmd) == -1)

        printf("execute: fork failed");

    default:

  }

  return;

}

Instead of using system() after fork(), try using one of the exec() functions after fork().

or call exit() after youve run the command, although exec would be better. the problem is 2 processes are returning from your function both trying to access the Display* returned by XOpenDisplay which is confusing X.

exec appears more straightforward, but 'execlp("sh", "-c", "du -sh /", NULL)' says 'du -sh /: command not found'. I don't want to seperate the arguments myself as I don't know how many will be entered in.

Anyways, system() by itself with an '&' appears to work, but I keep getting random "Segmentation Fault"s. I think it is because I did not add the '&' properly.

Also, while using fork(), do I have to worry about zombie processes or anything like that?

Here is the function using 'execlp':

Code:

void execute(const char *cmd)

{

  switch(fork())  

  {

    case -1:

      perror("execute: fork");

      return;

    case 0:  

      if (execlp("sh", "-c ",  cmd, NULL) == -1)

        perror("execute: exec() failed");

      default:  

  }

  return;

}

Here is the function using system() with '&':

Code:

void execute(const char *cmd)

{

  char * copy = malloc(sizeof(cmd) + sizeof(char));

  strcpy(copy, cmd);

  strcat(copy, '&');

  system(copy);

  free(copy);

  return;

}