Wait system call

how does wait system call works ?

#include <stdio.h>#include <unistd.h>#include <sys/wait.h>
int main(){
    // it can be any positive or non negative number     int pid = fork();    //if pid is zero the child process is created    if(pid == 0){        //get pid get's the id of the paricular process        //get ppid get's the id of the parent's process        printf(" child process id : %d has parent id : %d  \n", getpid(),getppid());    }else if(pid > 0){        printf(" parent process id : %d has  grand parent id : %d  \n", getpid(),getppid());      }else{        printf("process has not been created \n");    }}
 /* gauravtewari@Gauravs-MacBook-Air  ~/Desktop/os/wait  .aout                                                                                                                         ✔  626  12:13:48 parent process id : 67596 has  grand parent id : 57026   child process id : 67598 has parent id : 1   */

here parent is executing first then child is executing for this we can use wait () system call

#include <stdio.h>#include <unistd.h>#include <sys/wait.h>
int main(){
   // it can be any positive or non negative number    int pid = fork();   //if pid is zero the child process is created   if(pid == 0){       //get pid get's the id of the paricular process       //get ppid get's the id of the parent's process       printf(" child process id : %d has parent id : %d  \n", getpid(),getppid());   }else if(pid > 0){       wait(NULL);       printf(" parent process id : %d has  grand parent id : %d  \n", getpid(),getppid());    }else{       printf("process has not been created \n");   }}/*gauravtewari@Gauravs-MacBook-Air  ~/Desktop/os/wait  ./a.out                                                                                                                         ✔  631  12:17:32child process id : 68506 has parent id : 68504  parent process id : 68504 has  grand parent id : 57026  */

sleep will put a program on hold and after that other processes would be executed

 #include <stdio.h>#include <unistd.h>#include <sys/wait.h>
int main(){
   // it can be any positive or non negative number    int pid = fork();   //if pid is zero the child process is created   if(pid == 0){       //get pid get's the id of the paricular process       //get ppid get's the id of the parent's process       wait(5);       printf(" child process id : %d has parent id : %d  \n", getpid(),getppid());   }else if(pid > 0){       wait(NULL);       printf(" parent process id : %d has  grand parent id : %d  \n", getpid(),getppid());    }else{       printf("process has not been created \n");   }}