I have two cods the first one is for the parent which sends a signal ( SIGUSER1
) to the child and when the child receive it he should print that he received it.
Parent code
#include <stdio.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <unistd.h>
#include <sys/types.h>
void sighand(int);
int main()
{
int cpid, ppid;
ppid = getpid();
printf("My process ID is %d\n", ppid);
FILE *fp1;
fp1 = fopen("cpid.txt", "w+");
cpid = fork();
if ( cpid == 0 ) {
printf("I am the child => PID = %d\n", getpid());
}
else
printf("I am the parent => PID = %d, child ID = %d\n", getpid(), cpid);
fprintf(fp1, "%d\n", cpid);
// kill(cpid, SIGUSR1);//id, signal, send
sigset(SIGUSR2, sighand);
return 0;
}
void sighand(int the_sig){
if (the_sig == SIGUSR2){
printf("sigusr2 received");
exit(1);
}
}
Child code
#include <stdio.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <unistd.h>
#include <sys/types.h>
void sighand1(int);
int main()
{
FILE *fp1;
int pid;
fp1 = fopen("cpid.txt", "r");
fscanf(fp1, "%d,", &pid);
sigset(SIGUSR1,sighand1);
while(1) {
printf("Waiting..");
sigpause(SIGUSR1);
}
return 0;
}
void sighand1(int the_sig)
{
if (the_sig == SIGUSR1){
printf("sigusr1 received");
exit(1);
}
}
When I start the code it prints that the process (child) was created then when I send a signal it wont do any thing the child stuck in a loop or the wait and the parent wont do anything can any one tell me where did i go wrong in my code or logic.
Your code has several problems:
getppid()
function (get parent id) So your code can be corrected this way:
#include <stdio.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <unistd.h>
#include <sys/types.h>
#include <signal.h>
void parent_handler(int the_sig)
{
if (the_sig == SIGUSR2){
printf("sigusr2 received in parent\n");
}
}
void child_handler(int the_sig)
{
if (the_sig == SIGUSR1){
printf("sigusr1 received in child\n");
kill(getppid(), SIGUSR2);
exit(1);
}
}
int child_function()
{
/* prepare to receive signal */
sigset(SIGUSR1,child_handler);
while(1) {
printf("Waiting..");
fflush(stdout);
/* wait for signal */
sigpause(SIGUSR1);
}
return 0;
}
int main()
{
int cpid, ppid;
ppid = getpid();
printf("My process ID is %d\n", ppid);
cpid = fork();
if ( cpid == 0 ) {
printf("I am the child => PID = %d\n", getpid());
child_function();
return 0;
}
else
printf("I am the parent => PID = %d, child ID = %d\n", getpid(), cpid);
/* child will never reach this point */
sleep(1);
/* prepare parent to received signal */
sigset(SIGUSR2, parent_handler);
/* send signal to child */
kill(cpid, SIGUSR1);
sleep(1);
return 0;
}
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.