Question

Part 1

Write a program where a child is created to execute command that tells you the date and time in

Unix. Use ​execl(...)​. Note: you need to specify the full path of the file name that gives you date and time information. Announce the successful forking of child process by displaying its PID.

Part 2

Write a program where a child is created to execute a command that shows all files (including hidden files) in a directory with information such as permissions, owner, size, and when last modified. Use ​execvp(...)​. Announce the successful forking of child process by displaying its PID.

Part 3
[Step 1] Process_P1.c:

Create two files namely, ​destination1.txt ​and ​destination2.txt ​with read, write and execute permissions.

[Step 2] Process_P2.c: ​Copy the contents of ​source.txt​ ​into ​destination1.txt ​and ​destination2.txt ​as per the following procedure:

1. Read the next 50 characters from ​source.txt​, and among those characters write chars 5 and 8 only to ​destination1.txt

​2. Then the next 100 characters are read from ​source.txt​ and written in ​destination2.txt.

C program

Need Process_P2 only

Answer 1

Working code implemented in C and appropriate comments provided for better understanding.

Here I am attaching code for all files:

• Process_P1.c
• Process_P2.c
• Parent_Process.c

Process_P1.c:

#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>

int main(void)
{
   int fd_1, fd_2;
   errno = 0;

   // Opens and creates "destination1.txt" with read-write permissions
   fd_1 = open("destination1.txt", O_CREAT | O_RDWR, S_IRWXU);

   if (fd_1 == -1) {
       printf("Failed to open with error [%s]\n", strerror(errno));
   }
   else {
       printf("Destination 1: Opened\n");
   }
   close(fd_1);

   // Opens and creates "destination2.txt" with read-write permissions
   fd_2 = open("destination2.txt", O_CREAT | O_RDWR, S_IRWXU);

   if (fd_2 == -1) {
       printf("\n Failed to open with error [%s]\n", strerror(errno));
   }
   else {
       printf("Destination 2: Opened\n");
   }
   close(fd_2);

return 0;
}

Process_P2.c:

#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>

int main(void)
{
   int src, rd, acs, destination1, destination2;

   src = open("source.txt", O_RDONLY);

   destination1 = open("destination1.txt", O_CREAT | O_RDWR, S_IRWXU);
   destination2 = open("destination2.txt", O_CREAT | O_RDWR, S_IRWXU);

   if (src == -1 && destination1 == -1 && destination2 == -1)
   {
       printf("Error: [%s]\n", strerror(errno));
   }
   else{

       // Array of index size 101 allows it to read through 100 characters
       char buffer[101];
       int n = 101;

       while ( (rd = read(src, buffer, n)) > 0){

           if (n == 101) {

               for (int i = 0; i < sizeof(buffer); i++){
                   // Checks first 100 characters. If a '1' is found, it will be replaced with an 'A' in destination1.txt
                   if (buffer[i] == '1')
                       buffer[i] = 'A';

               }

               write(destination1, buffer, rd);
               n = 51;
           }
           else{
               for (int i = 0; i < sizeof(buffer); i++){
                   if (buffer[i] == '2')
                       buffer[i] = 'B';
               }

               write(destination2, buffer, rd);
               n = 101;
           }
       }
   }

   close(src);
   close(destination1);
   close(destination2);

   return 0;
}

Parent_Process.c:

#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>

int main(void)
{
   int pid_1, pid_2;

   // Child 1 created
   pid_1 = fork();

   if(pid_1 == 0) {

       // Child 1 Process
       printf("Child 1\n");
       char *const argv[] = {"Process_P1", NULL};

       execv(argv[0], argv);
       printf("EXECV Failed! Did you compile Prcs_P1.c yet? \n");

   }
   else {
       // 1 second wait time before processing second child
       sleep(1);
       pid_2 = fork();

       if (pid_2 == 0) {

           // Child 2 Process
           printf("Child 2\n");
           char *const argv[] = {"Process_P2", NULL};

           execv(argv[0], argv);
           printf("EXECV Failed! Did you compile Process_P2.c yet? \n");
       }
   }
   return 0;

}