Шрифт:
int main {
int file_desc;
struct flock region_to_lock;
int res;
file_desc = open(test_file, O_RDWR | O_CREAT, 0666);
if (!file_desc) {
fprintf(stderr, "Unable to open %s for read/write\n", test_file);
exit(EXIT_FAILURE);
}
В оставшейся части программы задаются разные участки файла, и делается попытка установить для них блокировки разных типов:
region_to_lock.l_type = F_RDLCK;
region_to_lock.l_whence = SEEK_SET;
region_to_lock.l_start = 10;
region_to_lock.l_len = 5;
printf("Process %d, trying F_RDLCK, region %d to %d\n", getpid, (int)region_to_lock.l_start,
(int)(region_to_lock.l_start + region_to_lock.l_len));
res = fcntl(file_desc, F_SETLK, ®ion_to_lock);
if (res == -1) {
printf("Process %d - failed to lock region\n", getpid);
} else {
printf("Process %d — obtained lock region\n", getpid);
}
region_to_lock.l_type = F_UNLCK;
region_to_lock.l_whence = SEEK_SET;
region_to_lock.l_start = 10;
region_to_lock.l_len = 5;
printf("Process %d, trying F_UNLCK, region %d to %d\n", getpid, (int)region_to_lock.l_start,
(int)(region_to_lock.l_start + region_to_lock.l_len));
res = fcntl(file_desc, F_SETLK, ®ion_to_lock);
if (res == -1) {
printf("Process %d — failed to unlock region\n", getpid);
} else {
printf("Process %d — unlocked region\n", getpid);
}
region_to_lock.l_type = F_UNLCK;
region_to_lock.l_whence = SEEK_SET;
region_to_lock.l_start = 0;
region_to_lock.l_len = 50;
printf("Process %d, trying F_UNLCK, region %d to %d\n", getpid", (int)region_to_lock.l_start,
(int)(region_to_lock.l_start + region_to_lock.l_len));
res = fcntl(file_desc, F_SETLK, ®ion_to_lock);
if (res == -1) {
printf("Process %d — failed to unlock region\n", getpid);
} else {
printf("Process %d — unlocked region\n", getpid);
}
region_to_lock.l_type = F_WRLCK;
region_to_lock.l_whence = SEEK_SET;
region_to_lock.lstart = 16;
region_to_lock.l_len = 5;
printf("Process %d, trying F_WRLCK, region %d to %d\n", getpid, (int)region_to_lock.l_start,
(int)(region_to_lock.l_start + region_to_lock.l_len));
res = fcntl(file_desc, F_SETLK, ®ion_to_lock);
if (res == -1) {
printf("Process %d — failed to lock region\n", getpid);
} else {
printf("Process %d — obtained lock on region\n", getpid);
}
region_to_lock.l_type = F_RDLCK;
region_to_lock.l_whence = SEEK_SET;
region_to_lock.l_start = 40;
region_to_lock.l_len = 10;
printf("Process %d, trying F_RDLCK, region %d to %d\n", getpid, (int)region_to_lock.l_start,
(int)(region_to_lock.l_start + region_to_lock.l_len));
res = fcntl(filedesc, F_SETLK, ®ion_to_lock);
if (res == -1) {
printf("Process %d — failed to lock region\n", getpid);
} else {
printf("Process %d — obtained lock on region\n", getpid);