Process communication with semaphore in C - c

Question

I'm writing two files:
a father.c with a parent process, and a son.c with a child process. They should use semaphore for synchronization. When I launch the father (compiled), the father process waits forever after the child process message:
Child ftok done.
father.c
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
typedef union _semun {
int val;
struct semid_ds *buf;
ushort *array;
} semun;
int initsem(key_t key){
int status = 0, semid;
semid = semget(key, 1, 0600 | IPC_CREAT | IPC_EXCL);
if(semid == -1){
if(errno == EEXIST){
semid = semget(key, 1, 0);
}
else{
semun arg;
arg.val = 1;
status = semctl(semid, 0, SETVAL, arg);
}
if(semid == -1 || status == -1){
perror("initsem failed\n");
return -1;
}
return (semid);
}
}
int waitSem(int semid) {
struct sembuf wait_buf;
wait_buf.sem_num = 0;
wait_buf.sem_op = -1;
if(semop(semid, &wait_buf, 1) == -1) {
perror("waitSem failed");
exit(1);
}
return(0);
}
int signalSem(int semid) {
struct sembuf signal_buf;
signal_buf.sem_num = 0;
signal_buf.sem_op = 1;
if(semop(semid, &signal_buf, 1) == -1) {
perror("signalSem failed");
exit(1);
}
return(0);
}
int main(){
pid_t pid;
key_t key;
int semid;
if(key = ftok("/home/user/Scrivania/test.txt", 'a') == -1){
perror("IPC error: ftok\n");
exit(1);
}
else{
printf("Ftok done\n");
}
semid = initsem(key);
pid = fork();
if(pid < 0){
printf("failed fork()\n");
}
else if(pid == 0){
printf("Child process with PID: %d\n", pid);
execl("/home/user/Desktop/son", "son", "",(char *)0);
}
else{
printf("Father process with PID: %d\n", pid);
printf("Waiting for my son\n");
waitSem(semid);
printf("My son has done\n");
signalSem(semid);
}
return 0;
}
son.c
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
typedef union _semun {
int val;
struct semid_ds *buf;
ushort *array;
} semun;
int initsem(key_t key){
int status = 0, semid;
semid = semget(key, 1, 0600 | IPC_EXCL);
if(semid == -1){
if(errno == EEXIST){
semid = semget(key, 1, 0);
}
else{
semun arg;
arg.val = 1;
status = semctl(semid, 0, SETVAL, arg);
}
if(semid == -1 || status == -1){
perror("initsem failed\n");
return -1;
}
return (semid);
}
}
int waitSem(int semid) {
struct sembuf wait_buf;
wait_buf.sem_num = 0;
wait_buf.sem_op = -1;
if(semop(semid, &wait_buf, 1) == -1) {
perror("waitSem failed");
exit(1);
}
return(0);
}
int signalSem(int semid) {
struct sembuf signal_buf;
signal_buf.sem_num = 0;
signal_buf.sem_op = 1;
if(semop(semid, &signal_buf, 1) == -1) {
perror("signalSem failed");
exit(1);
}
return(0);
}
int main(){
pid_t pid;
key_t key;
int semid;
if(key = ftok("/home/user/Desktop/test.txt", 'a') == -1){
perror("IPC error: ftok\n");
exit(1);
}
else{
printf("Ftok done\n");
}
semid = initsem(key);
waitSem(semid);
printf("Pre signal\n");
signalSem(semid);
printf("My operation\n");
return 0;
}