Question

Modify the below program so that the following two conditions are met:

1. Each child terminates abnormally after attempting to write to a location in the read-only text segment.

2. The parent prints output that is identical (except for the PIDs) to the following:

child 12255 terminated by signal 11: Segmentation fault

child 12254 terminated by signal 11: Segmentation fault

Hint: Read the man page for psignal(3)

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#include <stdlib.h>

#include <unistd.h>

#include <stdio.h>

#include <string.h>

#include <errno.h>

#include <sys/types.h>

#include <sys/wait.h>

void unix_error(char *msg) /* unix-style error */

{

fprintf(stderr, "%s: %s\n", msg, strerror(errno));

exit(0);

}

#define N 2

int main()

{

int status, i;

__pid_t pid;

/* Parent creates N children */

for (i = 0; i < N; i++)

if ((pid = fork()) == 0) /* child */

exit(100+i);

/* Parent reaps N children in no particular order */

while ((pid = waitpid(-1, &status, 0)) > 0) {

if (WIFEXITED(status))

printf("child %d terminated normally with exit status=%d\n",

pid, WEXITSTATUS(status));

else

printf("child %d terminated abnormally\n", pid);

}

/* The normal termination is if there are no more children */

if (errno != ECHILD)

unix_error("waitpid error");

exit(0);

}

Answer 1

Answer:

Please find the complete program for the question below.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>        /* psignal */
#include <sys/types.h> /* waitpid */
#include <sys/wait.h>    /* waitpid */

#define N 2

int main() {
      
        int status, i;
        pid_t pid[N], retpid;

        /* Parent creates N children */
        for(i = 0; i < N; i++) {
                if((pid[i] = fork()) == 0) { /* child */
                        strcpy("Hello", "World");    /* Writing on read-only location. It creates SIGSEGV */
                        exit(100 + i);
                }
        }

        /* Parent reaps N children in order */
        i = 0;
        while ((retpid = waitpid(pid[i++], &status, 0)) > 0) {
                if(WIFEXITED(status))
                        printf("child %d terminated normally with exit status=%d\n", retpid, WEXITSTATUS(status));
                else if(WIFSIGNALED(status)) {            /* Exited with a signal */
                        printf("child %d terminated by signal %d: \n", retpid, SIGSEGV);
                        psignal(WTERMSIG(status), NULL);
                }
                else
                        printf("child %d terminated abnormally \n", retpid);
        }

        /* The only normal termination is if there are no more children */
        if(errno != ECHILD)
                printf("waitpid error");

        exit(0);
}