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plurals

PO
primarykey
Id
171502
data
AcceptedAnswerId
0
AnswerCount
0
ClosedDate
CommentCount
0
CommunityOwnedDate
CreationDate
2008-10-05T04:41:43.623
FavoriteCount
0
LastActivityDate
2008-10-05T04:41:43.623
LastEditDate
LastEditorUserId
0
OwnerUserId
25222
ParentId
35380
PostTypeId
2
Score
4
ViewCount
0
LastEditorDisplayName
text
Body
It would probably be more beneficial for you provide what you have so far and explain what doesn't work as expected but here is what I came up with: <pre><code>#include <stdio.h> #include <sys/types.h> #include <unistd.h> #include <signal.h> #include <stdlib.h> #define READY_SIGNAL SIGUSR1 /* The ready flag is set when READY_SIGNAL is received. * It is needed so that when we wake up from sigsuspend * we know whether or not the signal received was READY_SIGNAL. */ volatile sig_atomic_t ready; void make_ready(int i) { ready = 1; } int main (int argc, char *argv[]) { pid_t cpid, ppid; /* pids of the child and parent */ /* Signal masks for sigprocmask and sigsuspend */ sigset_t block_mask, wait_mask; unsigned long c = 1; /* The counter */ unsigned long n = 100; /* The default max count value */ struct sigaction act; /* Override the default max count if provided */ if (argv[1]) n = strtoul(argv[1], NULL, 10); /* Prepare signal masks */ sigemptyset(&wait_mask); sigemptyset(&block_mask); sigaddset(&block_mask, READY_SIGNAL); /* Set the signal mask for the parent to ignore READY_SIGNAL until * we are ready to receive it, the mask will be inherited by the child, * needed to avoid race conditions */ sigprocmask(SIG_BLOCK, &block_mask, NULL); /* Register the signal handler, will be inherited by the child */ act.sa_flags = 0; act.sa_handler = make_ready; sigemptyset(&act.sa_mask); sigaction(READY_SIGNAL, &act, NULL); /* Get the parent's process id, needed for the child to send signals * to the parent process, could alternatively use getppid in the child */ ppid = getpid(); /* Call fork, storing the child's process id needed for the parent to * send signals to the child */ cpid = fork(); if (cpid < 0) { perror("Fork failed"); exit(EXIT_FAILURE); } if (cpid == 0) { /* Child */ c = 2; /* Child's first number will always be 2 */ if (c > n) exit(0); /* If c > n we have nothing to do */ do { /* Suspend until we receive READY_SIGNAL */ while (!ready) sigsuspend(&wait_mask); /* Print out number, flush for proper output sequencing when output is not a terminal. */ printf("Child: %lu\n", c); fflush(stdout); ready = 0; /* Reset ready flag */ c += 2; /* Increment counter */ /* Wake up parent process */ kill(ppid, READY_SIGNAL); } while (c <= n); } else { /* Parent */ for (;;) { /* Print out number, flush for proper output sequencing when output is not a terminal. */ printf("Parent: %lu\n", c); fflush(stdout); c += 2; /* Increment counter */ kill(cpid, READY_SIGNAL); /* Wake up child process */ if (c > n) break; /* Don't go back to sleep if we are done */ ready = 0; /* Reset ready flag */ /* Suspend until we receive READY_SIGNAL */ while (!ready) sigsuspend(&wait_mask); }; wait4(cpid, NULL, 0); /* Don't exist before child finishes */ } return 0; } </code></pre> This passes these basic tests: <code>./print_with_signals 100000|sort -n -k 2 -c && echo "Success"</code> <code>./print_with_signals 100001|sort -n -k 2 -c && echo "Success"</code>
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Title
singulars
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1. This table or related slice is empty.
PostParentId
1. POPrint Odd-Even numbers using signals
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1. PTAnswer
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1. This table or related slice is empty.
UserOwnerUserId
1. USRobert Gamble
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1. VO
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 VTUpMod
2. VO
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3. VO
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1. This table or related slice is empty.

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