C/Zombies
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| − | + | The code below will quickly tidy up after zombie children, and at the same time check for incoming data. | |
| − | * Assume | + | * Assume <code>sock</code> is the file descriptor that you wish to read from<br> |
| − | * | + | * <code>children</code> is incremented when you call <code>fork()</code> |
| − | + | <source lang="c"> | |
/* tidy up after children, but accept new data if its there! */ | /* tidy up after children, but accept new data if its there! */ | ||
while (children) { | while (children) { | ||
| Line 11: | Line 11: | ||
/* check if any children have become zombies! */ | /* check if any children have become zombies! */ | ||
| − | pid = waitpid(-1,& | + | pid = waitpid(-1,&status,WNOHANG | WUNTRACED); |
| − | if (pid | + | if (pid > 0) { |
children--; | children--; | ||
| − | printf( | + | printf("*** Child Died *** PID: %-6d Status: %-3d Children: %-2d\n",pid,WEXITSTATUS(status),children); |
/* if there are no children left, will break | /* if there are no children left, will break | ||
if there are more zombie children will tidy up before looking for data */ | if there are more zombie children will tidy up before looking for data */ | ||
| Line 21: | Line 21: | ||
/* timeout on the socket every 0.5sec */ | /* timeout on the socket every 0.5sec */ | ||
| − | memset(& | + | memset(&timeout,0,sizeof(timeout)); |
timeout.tv_usec = 500000; | timeout.tv_usec = 500000; | ||
| − | FD_ZERO(& | + | FD_ZERO(&toset); |
| − | FD_SET(sock,& | + | FD_SET(sock,&toset); |
/* check if there is data in the socket to be read... */ | /* check if there is data in the socket to be read... */ | ||
| − | if ((read = select(sock+1,& | + | if ((read = select(sock+1,&toset,NULL,NULL,&timeout)) == -1) { |
| − | perror( | + | perror("select()"); |
break; | break; | ||
} else if (read != 0) { | } else if (read != 0) { | ||
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} | } | ||
} | } | ||
| − | + | </source> | |
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Latest revision as of 17:06, 14 February 2013
The code below will quickly tidy up after zombie children, and at the same time check for incoming data.
- Assume
sockis the file descriptor that you wish to read from
-
childrenis incremented when you callfork()
/* tidy up after children, but accept new data if its there! */ while (children) { int pid, status, read; struct timeval timeout; fd_set toset; /* check if any children have become zombies! */ pid = waitpid(-1,&status,WNOHANG | WUNTRACED); if (pid > 0) { children--; printf("*** Child Died *** PID: %-6d Status: %-3d Children: %-2d\n",pid,WEXITSTATUS(status),children); /* if there are no children left, will break if there are more zombie children will tidy up before looking for data */ continue; } /* timeout on the socket every 0.5sec */ memset(&timeout,0,sizeof(timeout)); timeout.tv_usec = 500000; FD_ZERO(&toset); FD_SET(sock,&toset); /* check if there is data in the socket to be read... */ if ((read = select(sock+1,&toset,NULL,NULL,&timeout)) == -1) { perror("select()"); break; } else if (read != 0) { /* something can be read! */ break; } }
