Kim, a user, took a laptop on vacation and made changes to the configuration in order to use the device at the hotel. She can re
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Answer:
I am writing a C++ code.
#include <iostream> // for input output functions
using namespace std; // identifies objects like cin cout
int main() { //start of main() function body
string c_string; // stores the string entered by user from land water or air
int land=0; // contains the number of times land string is read in
int air=0; //contains the number of times air string is read in
int water = 0; //contains the number of times water string is read in
cin>>c_string; //reads the string entered by user from air water or land
/*while loop continues to execute until user enters xxxxx or maximum length of a string exceeds 8 */
while(c_string!= "xxxxx" && c_string.length()<=8) {
if(c_string=="land"){ // if string entered by user is land
land = land + 1;} //counts and increments each occurrence of land string by 1
else if(c_string=="air"){// if string entered by user is air
air = air + 1;}// counts and increments each occurrence of string air by 1
else if(c_string=="water"){// if string entered by user is water
water = water + 1;}//counts and increments each occurrence of air by 1
cin>>c_string;}
/* keeps reading the string entered by user from land air or water, until the loop breaks after the user enters xxxxx or user enters a string whose length is greater than 8 */
//prints the number of times land, air and water are read in
cout << "land:"<<land;
cout << endl<<"air:"<<air;
cout << endl<< "water:"<<water; }
Explanation:
Everything is well explained in the comments above.
The program prompts the user to input strings. These strings are either land air or water. The while loop continues to read the input strings until user enters xxxxx or the string entered by user exceeds the length 8. Both these terminating conditions are added in the while loop. After the loop terminates, the number of times land, air and water strings are read is displayed on the output screen. Any other string entered by user other than these 3 is ignored. The program along with the output is attached.
Answer:
a)
#include<stdio.h>
#include<stdlib.h>
#include<fcntl.h>
#include<unistd.h>
#define BUFSIZE 16
int main(){
//pipe descriptors
char msg[BUFSIZE];
char buf[BUFSIZE];
int pipefd[2];
if(pipe(pipefd) == -1){
//pipe creation error
perror("pipe");
exit(EXIT_FAILURE);
}
//pipe creation successfull
//write four messages
sprintf(msg , "apple");
write(pipefd[1], msg, BUFSIZE);
printf("Written %s\n", msg);
sprintf(msg , "boy");
write(pipefd[1], msg, BUFSIZE);
printf("Written %s\n", msg);
sprintf(msg , "cat");
write(pipefd[1], msg, BUFSIZE);
printf("Written %s\n", msg);
sprintf(msg , "dog");
write(pipefd[1], msg, BUFSIZE);
printf("Written %s\n", msg);
//read
read(pipefd[0], buf, BUFSIZE);
printf("Read: %s\n", buf);
read(pipefd[0], buf, BUFSIZE);
printf("Read: %s\n", buf);
read(pipefd[0], buf, BUFSIZE);
printf("Read: %s\n", buf);
read(pipefd[0], buf, BUFSIZE);
printf("Read: %s\n", buf);
close(pipefd[0]);
close(pipefd[1]);
return 0;
}
(b)
#include<stdio.h>
#include<stdlib.h>
#include<fcntl.h>
#include<unistd.h>
#include<wait.h>
#define BUFSIZE 16
int main(){
//pipe descriptors
char msg[BUFSIZE];
char buf[BUFSIZE];
int pipefd[2];
if(pipe(pipefd) == -1){
//pipe creation error
perror("pipe");
exit(EXIT_FAILURE);
}
//pipe creation successfull
//write four messages
if(fork() == 0){
//this is child
//close unused write end
close(pipefd[1]);
read(pipefd[0], buf, BUFSIZE);
printf("This is child process reading first message. Content is %s\n", buf);
read(pipefd[0], buf, BUFSIZE);
printf("This is child process reading second message. Content is %s\n", buf);
read(pipefd[0], buf, BUFSIZE);
printf("This is child process reading third message. Content is %s\n", buf);
read(pipefd[0], buf, BUFSIZE);
printf("This is child process reading fourth message. Content is %s\n", buf);
close(pipefd[0]);
//exit from child
exit(EXIT_SUCCESS);
}
//this is parent process
//close unused read end
close(pipefd[0]);
sprintf(msg , "apple");
printf("This is parent process. Writing first message into pipe\n");
write(pipefd[1], msg, BUFSIZE);
sprintf(msg , "boy");
printf("This is parent process. Writing second message into pipe\n");
write(pipefd[1], msg, BUFSIZE);
sprintf(msg , "cat");
printf("This is parent process. Writing third message into pipe\n");
write(pipefd[1], msg, BUFSIZE);
sprintf(msg , "dog");
printf("This is parent process. Writing fourth message into pipe\n");
write(pipefd[1], msg, BUFSIZE);
close(pipefd[1]);
//wait for child
wait(NULL);
return 0;
}
(c)
#include<stdio.h>
#include<stdlib.h>
#include<fcntl.h>
#include<unistd.h>
#include<sys/wait.h>
#include<sys/types.h>
#include<signal.h>
typedef struct sigaction Sigaction;
unsigned long long size = 0;
void alarmhandler(int sig){
//alarm fired writing blocked
printf("Write blocked after %llu characters\n", size);
exit(EXIT_SUCCESS);
}
int main(){
//pipe descriptors
int pipefd[2];
if(pipe(pipefd) == -1){
//pipe creation error
perror("pipe");
exit(EXIT_FAILURE);
}
//install handler
sigset_t mask , prev;
sigemptyset(&mask);
sigaddset(&mask , SIGALRM);
sigprocmask(SIG_BLOCK , &mask , &prev);
Sigaction new_action;
sigemptyset(&new_action.sa_mask);
new_action.sa_flags = SA_RESTART;
new_action.sa_handler = alarmhandler;
sigaction(SIGALRM , &new_action , NULL);
sigprocmask(SIG_SETMASK , &prev, NULL);
while(1){
//print size on multiple of 4
if(size != 0 && size % 1024 == 0){
printf("%llu characters in pipe\n", size);
}
//reset previous alarm
alarm(0);
//set new alarm for 5 seconds
alarm(5);
//write to pipe one character
write(pipefd[1], "A", sizeof(char));
size++;
}
return 0;
}
Explanation:
Output for a, b, c are pasted accordingly
