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63c6479f5f004bf4898cf545

2023-02-15T03:22:46.497Z

Question from Code

v1

will this correctly remove the data in post? should i set it to null as well?

void free_posts(Post *post_ptr) { Post *curr = post_ptr; // Create a variable to traverse the linked list while (curr != NULL) { Post *temp_post = curr; // Create a temporary variable to hold a post curr = curr->next; if (temp_post != NULL) { // If the post is not null, free the post and its contents free(temp_post->date); free(temp_post->contents); free(temp_post); } } }

63c6479f5f004bf4898cf545

2023-02-15T03:26:39.358Z

Question from Code

v1

will this correctly remove the user and their posts

int delete_user(const char *name, User **user_ptr_del) { // Delete user from list User *curr = *user_ptr_del; // Variable to traverse the list User *temp = curr; // Variable to hold the deleted user // Check for empty users list if (*user_ptr_del == NULL) { return 1; } // Remove the user from all friendlists, and clear user's list of friends remove_friends(name, user_ptr_del); // If there is 1 element in the list if (curr->next == NULL) { if (strcmp(curr->name, name) == 0) { *user_ptr_del = NULL; free_posts(temp->first_post); // Free the memory of the posts of the deleted user if (temp != NULL) { free(temp); // Free the memory of the user } return 0; } else { return 1; } } // If 1st element is to be removed if (strcmp(curr->name, name) == 0) { *user_ptr_del = curr->next; free_posts(temp->first_post); // Free the memory of the posts of the deleted user if (temp != NULL) { free(temp); // Free the memory of the user } return 0; } // Iterate through the users until the end of the list is reached, // or until the name of curr matches the name of the deleted user while (strcmp(curr->next->name, name) != 0 && curr->next != NULL) { curr = curr->next; } // If name does not exist if (curr->next == NULL) { return 1; } if (curr->next->next == NULL) { // If the last user is to be removed temp = curr->next; curr->next = NULL; } else { temp = curr->next; // If the user to be removed is in the middle of the list curr->next = curr->next->next; } free_posts(temp->first_post); // Free the memory of the posts of the deleted user // Free the memory in temp if (temp != NULL) { free(temp); temp = NULL; } return 0; }

63c6479f5f004bf4898cf545

2023-02-15T03:27:30.816Z

Question from Code

v1

why is it that when i add a post to the user, delete the user and add back the user with the same name,their posts are still there

int delete_user(const char *name, User **user_ptr_del) { // Delete user from list User *curr = *user_ptr_del; // Variable to traverse the list User *temp = curr; // Variable to hold the deleted user // Check for empty users list if (*user_ptr_del == NULL) { return 1; } // Remove the user from all friendlists, and clear user's list of friends remove_friends(name, user_ptr_del); // If there is 1 element in the list if (curr->next == NULL) { if (strcmp(curr->name, name) == 0) { *user_ptr_del = NULL; free_posts(temp->first_post); // Free the memory of the posts of the deleted user if (temp != NULL) { free(temp); // Free the memory of the user } return 0; } else { return 1; } } // If 1st element is to be removed if (strcmp(curr->name, name) == 0) { *user_ptr_del = curr->next; free_posts(temp->first_post); // Free the memory of the posts of the deleted user if (temp != NULL) { free(temp); // Free the memory of the user } return 0; } // Iterate through the users until the end of the list is reached, // or until the name of curr matches the name of the deleted user while (strcmp(curr->next->name, name) != 0 && curr->next != NULL) { curr = curr->next; } // If name does not exist if (curr->next == NULL) { return 1; } if (curr->next->next == NULL) { // If the last user is to be removed temp = curr->next; curr->next = NULL; } else { temp = curr->next; // If the user to be removed is in the middle of the list curr->next = curr->next->next; } free_posts(temp->first_post); // Free the memory of the posts of the deleted user // Free the memory in temp if (temp != NULL) { free(temp); temp = NULL; } return 0; }

63c6479f5f004bf4898cf545

2023-02-15T03:28:15.234Z

Question from Code

v1

do i need to call free_posts anywhere else to correctly remove the posts from the deleted user?

int delete_user(const char *name, User **user_ptr_del) { // Delete user from list User *curr = *user_ptr_del; // Variable to traverse the list User *temp = curr; // Variable to hold the deleted user // Check for empty users list if (*user_ptr_del == NULL) { return 1; } // Remove the user from all friendlists, and clear user's list of friends remove_friends(name, user_ptr_del); // If there is 1 element in the list if (curr->next == NULL) { if (strcmp(curr->name, name) == 0) { *user_ptr_del = NULL; free_posts(temp->first_post); // Free the memory of the posts of the deleted user if (temp != NULL) { free(temp); // Free the memory of the user } return 0; } else { return 1; } } // If 1st element is to be removed if (strcmp(curr->name, name) == 0) { *user_ptr_del = curr->next; free_posts(temp->first_post); // Free the memory of the posts of the deleted user if (temp != NULL) { free(temp); // Free the memory of the user } return 0; } // Iterate through the users until the end of the list is reached, // or until the name of curr matches the name of the deleted user while (strcmp(curr->next->name, name) != 0 && curr->next != NULL) { curr = curr->next; } // If name does not exist if (curr->next == NULL) { return 1; } if (curr->next->next == NULL) { // If the last user is to be removed temp = curr->next; curr->next = NULL; } else { temp = curr->next; // If the user to be removed is in the middle of the list curr->next = curr->next->next; } free_posts(temp->first_post); // Free the memory of the posts of the deleted user // Free the memory in temp if (temp != NULL) { free(temp); temp = NULL; } return 0; }

63c6479f5f004bf4898cf545

2023-02-15T03:29:13.633Z

Question from Code

v1

will this code correctly remove all the posts from the deleted user

void free_posts(Post *post_ptr) { Post *curr = post_ptr; // Create a variable to traverse the linked list while (curr != NULL) { Post *temp_post = curr; // Create a temporary variable to hold a post curr = curr->next; if (temp_post != NULL) { // If the post is not null, free the post and its contents free(temp_post->date); free(temp_post->contents); free(temp_post); } } } int delete_user(const char *name, User **user_ptr_del) { // Delete user from list User *curr = *user_ptr_del; // Variable to traverse the list User *temp = curr; // Variable to hold the deleted user // Check for empty users list if (*user_ptr_del == NULL) { return 1; } // Remove the user from all friendlists, and clear user's list of friends remove_friends(name, user_ptr_del); // If there is 1 element in the list if (curr->next == NULL) { if (strcmp(curr->name, name) == 0) { *user_ptr_del = NULL; free_posts(temp->first_post); // Free the memory of the posts of the deleted user if (temp != NULL) { free(temp); // Free the memory of the user } return 0; } else { return 1; } } // If 1st element is to be removed if (strcmp(curr->name, name) == 0) { *user_ptr_del = curr->next; free_posts(temp->first_post); // Free the memory of the posts of the deleted user if (temp != NULL) { free(temp); // Free the memory of the user } return 0; } // Iterate through the users until the end of the list is reached, // or until the name of curr matches the name of the deleted user while (strcmp(curr->next->name, name) != 0 && curr->next != NULL) { curr = curr->next; } // If name does not exist if (curr->next == NULL) { return 1; } if (curr->next->next == NULL) { // If the last user is to be removed temp = curr->next; curr->next = NULL; } else { temp = curr->next; // If the user to be removed is in the middle of the list curr->next = curr->next->next; } free_posts(temp->first_post); // Free the memory of the posts of the deleted user // Free the memory in temp if (temp != NULL) { free(temp); temp = NULL; } return 0; }

63c6479f5f004bf4898cf545

2023-02-15T03:30:40.092Z

Question from Code

v1

does this code properly create a post and add it to a user

int make_post(const User *author, User *target, char *contents) { // Check if users exist if (author == NULL || target == NULL) { return 2; } int friend_mutuality = 0; // A variable to track if users are friends // Check if author is friends with target for(int i = 0; i < MAX_FRIENDS; i++) { if (author->friends[i] == target) { friend_mutuality++; // Update the tracking variable } } if (friend_mutuality == 0) { return 1; } // Make a new post Post *new_post = malloc(sizeof(Post)); if (new_post == NULL) { perror("malloc"); exit(-1); } strcpy(new_post->author, author->name); // Set the post author new_post->contents = contents; // Set the post contents time_t *curr_time = malloc(sizeof(time_t)); // Set the post date if (curr_time == NULL) { perror("malloc"); exit(-1); } time(curr_time) ; new_post->date = curr_time; // If target has no posts, set the next post to NULL, // Otherwise, set the next post to the second most recent post if (target->first_post == NULL) { new_post->next = NULL; } else { new_post->next = target->first_post; } // Set the target's first post equal to newest post target->first_post = new_post; return 0; }

63c6479f5f004bf4898cf545

2023-02-15T03:31:42.373Z

Help Fix Code

v1

int make_post(const User *author, User *target, char *contents) { // Check if users exist if (author == NULL || target == NULL) { return 2; } int friend_mutuality = 0; // A variable to track if users are friends // Check if author is friends with target for(int i = 0; i < MAX_FRIENDS; i++) { if (author->friends[i] == target) { friend_mutuality++; // Update the tracking variable } } if (friend_mutuality == 0) { return 1; } // Make a new post Post *new_post = malloc(sizeof(Post)); if (new_post == NULL) { perror("malloc"); exit(-1); } strcpy(new_post->author, author->name); // Set the post author new_post->contents = contents; // Set the post contents time_t *curr_time = malloc(sizeof(time_t)); // Set the post date if (curr_time == NULL) { perror("malloc"); exit(-1); } time(curr_time) ; new_post->date = curr_time; // If target has no posts, set the next post to NULL, // Otherwise, set the next post to the second most recent post if (target->first_post == NULL) { new_post->next = NULL; } else { new_post->next = target->first_post; } // Set the target's first post equal to newest post target->first_post = new_post; return 0; }

create a post and add it to the user

63c6479f5f004bf4898cf545

2023-02-15T20:32:23.362Z

Question from Code

v1

why might this cause a segfault

int create_user(const char *name, User **user_ptr_add) { if (strlen(name) >= MAX_NAME) { // Check if name is too long return 2; } User *curr = *user_ptr_add; // Create a pointer curr to traverse the list // Create a new user User *new_user = malloc(sizeof(User)); if (new_user == NULL) { perror("malloc"); exit(-1); } strcpy(new_user->name, name); new_user->next = NULL; new_user->first_post = NULL; // If list is empty, make the head pointer equal to our new user if (*user_ptr_add == NULL) { *user_ptr_add = new_user; return 0; } while (curr->next != NULL) { // Traverse the list if (strcmp(name, curr->name) == 0) { // Check if name already exists return 1; } curr = curr->next; } if (strcmp(name, curr->name) == 0) { // Check if last user in the list has the same name return 1; } curr->next = new_user; // Make the last element equal to our new user return 0; }

63c6479f5f004bf4898cf545

2023-02-15T20:33:30.860Z

General Question

v1

how does strncpy work

63c6479f5f004bf4898cf545

2023-02-15T20:35:28.536Z

Question from Code

v1

how do i initialize the friendlist

int create_user(const char *name, User **user_ptr_add) { if (strlen(name) >= MAX_NAME) { // Check if name is too long return 2; } User *curr = *user_ptr_add; // Create a pointer curr to traverse the list // Create a new user User *new_user = malloc(sizeof(User)); if (new_user == NULL) { perror("malloc"); exit(-1); } strcpy(new_user->name, name); new_user->next = NULL; new_user->first_post = NULL; // If list is empty, make the head pointer equal to our new user if (*user_ptr_add == NULL) { *user_ptr_add = new_user; return 0; } while (curr->next != NULL) { // Traverse the list if (strcmp(name, curr->name) == 0) { // Check if name already exists return 1; } curr = curr->next; } if (strcmp(name, curr->name) == 0) { // Check if last user in the list has the same name return 1; } curr->next = new_user; // Make the last element equal to our new user return 0; }

63c6479f5f004bf4898cf545

2023-02-15T20:36:00.775Z

Question from Code

v1

how do i initialize curr->friends, which is an array

int create_user(const char *name, User **user_ptr_add) { if (strlen(name) >= MAX_NAME) { // Check if name is too long return 2; } User *curr = *user_ptr_add; // Create a pointer curr to traverse the list // Create a new user User *new_user = malloc(sizeof(User)); if (new_user == NULL) { perror("malloc"); exit(-1); } strcpy(new_user->name, name); new_user->next = NULL; new_user->first_post = NULL; // If list is empty, make the head pointer equal to our new user if (*user_ptr_add == NULL) { *user_ptr_add = new_user; return 0; } while (curr->next != NULL) { // Traverse the list if (strcmp(name, curr->name) == 0) { // Check if name already exists return 1; } curr = curr->next; } if (strcmp(name, curr->name) == 0) { // Check if last user in the list has the same name return 1; } curr->next = new_user; // Make the last element equal to our new user return 0; }

63c6479f5f004bf4898cf545

2023-02-15T20:37:16.349Z

Question from Code

v1

what should i initialize the array friends, which stores struct Users, to?

int create_user(const char *name, User **user_ptr_add) { if (strlen(name) >= MAX_NAME) { // Check if name is too long return 2; } User *curr = *user_ptr_add; // Create a pointer curr to traverse the list // Create a new user User *new_user = malloc(sizeof(User)); if (new_user == NULL) { perror("malloc"); exit(-1); } strcpy(new_user->name, name); new_user->next = NULL; new_user->first_post = NULL; // If list is empty, make the head pointer equal to our new user if (*user_ptr_add == NULL) { *user_ptr_add = new_user; return 0; } while (curr->next != NULL) { // Traverse the list if (strcmp(name, curr->name) == 0) { // Check if name already exists return 1; } curr = curr->next; } if (strcmp(name, curr->name) == 0) { // Check if last user in the list has the same name return 1; } curr->next = new_user; // Make the last element equal to our new user return 0; }

63c6479f5f004bf4898cf545

2023-02-15T20:37:49.513Z

Question from Code

v1

how do i intialize the array of users, curr->friends, to null

int create_user(const char *name, User **user_ptr_add) { if (strlen(name) >= MAX_NAME) { // Check if name is too long return 2; } User *curr = *user_ptr_add; // Create a pointer curr to traverse the list // Create a new user User *new_user = malloc(sizeof(User)); if (new_user == NULL) { perror("malloc"); exit(-1); } strcpy(new_user->name, name); new_user->next = NULL; new_user->first_post = NULL; // If list is empty, make the head pointer equal to our new user if (*user_ptr_add == NULL) { *user_ptr_add = new_user; return 0; } while (curr->next != NULL) { // Traverse the list if (strcmp(name, curr->name) == 0) { // Check if name already exists return 1; } curr = curr->next; } if (strcmp(name, curr->name) == 0) { // Check if last user in the list has the same name return 1; } curr->next = new_user; // Make the last element equal to our new user return 0; }

63c6479f5f004bf4898cf545

2023-02-15T20:39:08.068Z

General Question

v1

do i need to free memset

63c6479f5f004bf4898cf545

2023-02-15T20:44:15.645Z

Question from Code

v1

what is causing the segfault

int create_user(const char *name, User **user_ptr_add) { if (strlen(name) >= MAX_NAME) { // Check if name is too long return 2; } User *curr = *user_ptr_add; // Create a pointer curr to traverse the list // Create a new user User *new_user = malloc(sizeof(User)); if (new_user == NULL) { perror("malloc"); exit(-1); } strncpy(new_user->name, name, strlen(name)); new_user->next = NULL; new_user->first_post = NULL; memset(curr->friends, 0, sizeof(curr->friends)); // If list is empty, make the head pointer equal to our new user if (*user_ptr_add == NULL) { *user_ptr_add = new_user; return 0; } while (curr->next != NULL) { // Traverse the list if (strcmp(name, curr->name) == 0) { // Check if name already exists return 1; } curr = curr->next; } if (strcmp(name, curr->name) == 0) { // Check if last user in the list has the same name return 1; } curr->next = new_user; // Make the last element equal to our new user return 0; }

63c6479f5f004bf4898cf545

2023-02-15T20:44:45.565Z

General Question

v1

how do i initialize user_ptr_add

63c6479f5f004bf4898cf545

2023-02-15T20:45:35.390Z

Question from Code

v1

does user_ptr_add need to be initialized

int create_user(const char *name, User **user_ptr_add) { if (strlen(name) >= MAX_NAME) { // Check if name is too long return 2; } User *curr = *user_ptr_add; // Create a pointer curr to traverse the list // Create a new user User *new_user = malloc(sizeof(User)); if (new_user == NULL) { perror("malloc"); exit(-1); } strncpy(new_user->name, name, strlen(name)); new_user->next = NULL; new_user->first_post = NULL; memset(curr->friends, 0, sizeof(curr->friends)); // If list is empty, make the head pointer equal to our new user if (*user_ptr_add == NULL) { *user_ptr_add = new_user; return 0; } while (curr->next != NULL) { // Traverse the list if (strcmp(name, curr->name) == 0) { // Check if name already exists return 1; } curr = curr->next; } if (strcmp(name, curr->name) == 0) { // Check if last user in the list has the same name return 1; } curr->next = new_user; // Make the last element equal to our new user return 0; }

63c6479f5f004bf4898cf545

2023-02-15T20:46:01.463Z

Question from Code

v1

does curr->friends need to be initialized

int create_user(const char *name, User **user_ptr_add) { if (strlen(name) >= MAX_NAME) { // Check if name is too long return 2; } User *curr = *user_ptr_add; // Create a pointer curr to traverse the list // Create a new user User *new_user = malloc(sizeof(User)); if (new_user == NULL) { perror("malloc"); exit(-1); } strncpy(new_user->name, name, strlen(name)); new_user->next = NULL; new_user->first_post = NULL; memset(curr->friends, 0, sizeof(curr->friends)); // If list is empty, make the head pointer equal to our new user if (*user_ptr_add == NULL) { *user_ptr_add = new_user; return 0; } while (curr->next != NULL) { // Traverse the list if (strcmp(name, curr->name) == 0) { // Check if name already exists return 1; } curr = curr->next; } if (strcmp(name, curr->name) == 0) { // Check if last user in the list has the same name return 1; } curr->next = new_user; // Make the last element equal to our new user return 0; }

63c6479f5f004bf4898cf545

2023-02-15T20:46:24.771Z

Question from Code

v1

what code do i add to initialize curr->friends

int create_user(const char *name, User **user_ptr_add) { if (strlen(name) >= MAX_NAME) { // Check if name is too long return 2; } User *curr = *user_ptr_add; // Create a pointer curr to traverse the list // Create a new user User *new_user = malloc(sizeof(User)); if (new_user == NULL) { perror("malloc"); exit(-1); } strncpy(new_user->name, name, strlen(name)); new_user->next = NULL; new_user->first_post = NULL; memset(curr->friends, 0, sizeof(curr->friends)); // If list is empty, make the head pointer equal to our new user if (*user_ptr_add == NULL) { *user_ptr_add = new_user; return 0; } while (curr->next != NULL) { // Traverse the list if (strcmp(name, curr->name) == 0) { // Check if name already exists return 1; } curr = curr->next; } if (strcmp(name, curr->name) == 0) { // Check if last user in the list has the same name return 1; } curr->next = new_user; // Make the last element equal to our new user return 0; }

63c6479f5f004bf4898cf545

2023-02-15T20:46:42.863Z

Question from Code

v1

is line 17 correct

int create_user(const char *name, User **user_ptr_add) { if (strlen(name) >= MAX_NAME) { // Check if name is too long return 2; } User *curr = *user_ptr_add; // Create a pointer curr to traverse the list // Create a new user User *new_user = malloc(sizeof(User)); if (new_user == NULL) { perror("malloc"); exit(-1); } strncpy(new_user->name, name, strlen(name)); new_user->next = NULL; new_user->first_post = NULL; memset(curr->friends, 0, sizeof(curr->friends)); // If list is empty, make the head pointer equal to our new user if (*user_ptr_add == NULL) { *user_ptr_add = new_user; return 0; } while (curr->next != NULL) { // Traverse the list if (strcmp(name, curr->name) == 0) { // Check if name already exists return 1; } curr = curr->next; } if (strcmp(name, curr->name) == 0) { // Check if last user in the list has the same name return 1; } curr->next = new_user; // Make the last element equal to our new user return 0; }

63c6479f5f004bf4898cf545

2023-02-15T20:47:15.587Z

Question from Code

v1

why is memset(curr->friends, 0, sizeof(curr->friends)); causing the segfault

int create_user(const char *name, User **user_ptr_add) { if (strlen(name) >= MAX_NAME) { // Check if name is too long return 2; } User *curr = *user_ptr_add; // Create a pointer curr to traverse the list // Create a new user User *new_user = malloc(sizeof(User)); if (new_user == NULL) { perror("malloc"); exit(-1); } strncpy(new_user->name, name, strlen(name)); new_user->next = NULL; new_user->first_post = NULL; memset(curr->friends, 0, sizeof(curr->friends)); // If list is empty, make the head pointer equal to our new user if (*user_ptr_add == NULL) { *user_ptr_add = new_user; return 0; } while (curr->next != NULL) { // Traverse the list if (strcmp(name, curr->name) == 0) { // Check if name already exists return 1; } curr = curr->next; } if (strcmp(name, curr->name) == 0) { // Check if last user in the list has the same name return 1; } curr->next = new_user; // Make the last element equal to our new user return 0; }

63c6479f5f004bf4898cf545

2023-02-16T22:19:37.610Z

Explain Code

v1

#include <stdio.h> #define SIZE 4 #define OVERFLOW 5 int main() { int index = 0; int i; int before[SIZE] = {10, 10, 10, 10}; int a[SIZE] = {0, 0, 0, 0}; int after[SIZE] = {10, 10, 10, 10}; printf("Address of the variables:\n"); for (index = 0; index < SIZE; index++) { printf("%lx -> &after[%d]\n", (unsigned long) &after[index], index); } for (index = 0; index < SIZE; index++) { printf("%lx -> &a[%d]\n", (unsigned long) &a[index], index); } for (index = 0; index < SIZE; index++) { printf("%lx -> &before[%d]\n", (unsigned long) &before[index], index); } printf("%lx -> &i\n", (unsigned long)&i); printf("%lx -> &index\n", (unsigned long)&index); printf("\n"); printf("Initial values:\n"); printf("i = %d\n", i); printf("before = {%d, %d, %d, %d}\n", before[0], before[1], before[2], before[3]); printf("a = {%d, %d, %d, %d}\n", a[0], a[1], a[2], a[3]); printf("after = {%d, %d, %d, %d}\n", after[0], after[1], after[2], after[3]); printf("\n"); for (i = 0; i < OVERFLOW; i++) { a[i] = i * 10; printf("i = %d\n", i); printf("before = {%d, %d, %d, %d}\n", before[0], before[1], before[2], before[3]); printf("a = {%d, %d, %d, %d}\n", a[0], a[1], a[2], a[3]); printf("after = {%d, %d, %d, %d}\n", after[0], after[1], after[2], after[3]); } return 0; }

63c6479f5f004bf4898cf545

2023-02-16T22:20:28.404Z

Question from Code

v1

what is this code doing

#include <stdio.h> #define SIZE 4 #define OVERFLOW 5 int main() { int index = 0; int i; int before[SIZE] = {10, 10, 10, 10}; int a[SIZE] = {0, 0, 0, 0}; int after[SIZE] = {10, 10, 10, 10}; printf("Address of the variables:\n"); for (index = 0; index < SIZE; index++) { printf("%lx -> &after[%d]\n", (unsigned long) &after[index], index); } for (index = 0; index < SIZE; index++) { printf("%lx -> &a[%d]\n", (unsigned long) &a[index], index); } for (index = 0; index < SIZE; index++) { printf("%lx -> &before[%d]\n", (unsigned long) &before[index], index); } printf("%lx -> &i\n", (unsigned long)&i); printf("%lx -> &index\n", (unsigned long)&index); printf("\n"); printf("Initial values:\n"); printf("i = %d\n", i); printf("before = {%d, %d, %d, %d}\n", before[0], before[1], before[2], before[3]); printf("a = {%d, %d, %d, %d}\n", a[0], a[1], a[2], a[3]); printf("after = {%d, %d, %d, %d}\n", after[0], after[1], after[2], after[3]); printf("\n"); for (i = 0; i < OVERFLOW; i++) { a[i] = i * 10; printf("i = %d\n", i); printf("before = {%d, %d, %d, %d}\n", before[0], before[1], before[2], before[3]); printf("a = {%d, %d, %d, %d}\n", a[0], a[1], a[2], a[3]); printf("after = {%d, %d, %d, %d}\n", after[0], after[1], after[2], after[3]); } return 0; }

63c6479f5f004bf4898cf545

2023-02-16T22:34:35.498Z

Help Write Code

v1

Now start gdb again but before you start, run script gdb_example.txt to record your interaction. (You'll submit this interaction.) This time make sure you watch the array after. It is pretty slow to step through every line of your code, so use list to find the line number of the for loop where we start to assign values to the array. Set a breakpoint on that line number and also set a breakpoint somewhere before that line. Start your program using run and it should run up to the first breakpoint. Then use continue to jump to the second breakpoint you set which should be the for loop. At any point, you can use continue to execute up to the next breakpoint. If you tried it again now, it should jump to the second pass through the loop. Instead, use next to step through one line at a time. Watch the value of after[0] carefully. When it changes, print its address. (Yes, you can do "print &(after[0])" inside gdb.) Then, print the address of a[4]. Does that help you understand what happened? Exit gdb. (Say 'y' when it asks if you want to Quit anyway.) Then exit your script by typing exit. Make sure the script file you generated is named gdb_example.txt and add it to your repository. The last step is to try to make your program crash. (I had to set OVERFLOW to something like 5000 to get it to crash with a Segmentation fault.) Once you've found a value for OVERFLOW that produces a Segmentation fault, run the program in gdb without setting a breakpoint so that it runs automatically until the crash. Then use the backtrace command and the print command to investigate the value for i. Try backtrace full for even more helpful information. You don't need to record what you're doing on this step. We just want you to see the backtrace command.

63c6479f5f004bf4898cf545

2023-02-25T03:21:02.938Z

Help Write Code

v1

Your first task is to implement parse_file, so that it reads a makefile and constructs a corresponding linked data structure. The necessary structs are defined in pmake.h, and the comments at the top of the file explain what each line of a makefile will contain. You may not change the struct definitions. pmake.h also contains function prototypes for functions that are either already provided, or that you will need to write. The starter code also contains a makefile named handout.mk. (This file and the required source and header files are in the subdirectory handout_example. ) The picture above shows a data structure that could result from parsing this file. Notice that there is one struct rule_node for each rule in the original makefile and an additional struct rule_node for each dependency that is not also a target. You must follow this design. You are are also required to have the head of the list be the first rule in the original makefile. However, depending on how you do your parsing, the struct rule_node elements may come in a different order in your linked list of rules. Before reading any more of this handout, spend time to make sure you understand this figure and how it connects to the original makefile and the structs defined in pmake.h. You will see that the actions are stored in a struct action_node that has a member args. This array has the format required by the second parameter to execvp. Use the man page for execvp to understand this format. In particular, notice that the first element is the executable name, subsequent elements are the arguments for that executable, and these are followed by an extra NULL pointer element.

63c6479f5f004bf4898cf545

2023-02-25T03:42:43.884Z

General Question

v1

how do you read from an open file passed into as a parameter

63c6479f5f004bf4898cf545

2023-02-26T21:18:46.266Z

General Question

v1

when do we dereference variables?

63c6479f5f004bf4898cf545

2023-02-26T21:19:36.693Z

Question from Code

v1

in this code, why do we put a * in front of pt on line 5?

int num = 40; int *pt; pt = &num; int *anotherpt = &num; *pt = 30; printf("%d\n", *anotherpt); return 0;

63c6479f5f004bf4898cf545

2023-02-26T21:20:18.229Z

Question from Code

v1

what if we did pt = 30? does that work and why?

int num = 40; int *pt; pt = &num; int *anotherpt = &num; *pt = 30; printf("%d\n", *anotherpt); return 0;

63c6479f5f004bf4898cf545

2023-02-26T21:20:40.509Z

General Question

v1

when do we use &?

63c6479f5f004bf4898cf545

2023-02-26T22:20:43.472Z

Question from Code

v1

what would be the value of x[0]

char *result[2]; x = result[0]; // some hidden code result[0] = "read only"; y = x[0];

63c6479f5f004bf4898cf545

2023-02-26T22:58:55.322Z

Question from Code

v1

why dont we pass in &arr to function change

nt arr[3] = {1, 2, 3}; double result = change(arr, 3); // Comment the above, and uncomment the below, to see // change only work on the 2nd and 3rd integers // double result = change(arr + 1, 2); printf("The array is now: "); for(int i = 0; i < 3; i++) { printf("%d ", arr[i]); } printf("\nAnd the average is %lf\n", result);

63c6479f5f004bf4898cf545

2023-02-27T01:40:25.160Z

Question from Code

v1

whats wrong with this code

int *mkarray(int a, int b, int c) { int arr[3]; arr[0] = a; arr[1] = b; arr[2] = c; int *p = arr; return p; } // Code for other_function() omitted. int main() { int *ptr = mkarray(10, 20, 30); other_function(); printf("%d %d %d\n", ptr[0], ptr[1], ptr[2]); }

63c6479f5f004bf4898cf545

2023-02-27T01:44:48.421Z

General Question

v1

when should we be allocating heap space

63c6479f5f004bf4898cf545

2023-02-27T01:46:10.972Z

Question from Code

v1

why doesnt this need malloc

double change(int *a, int size) { double sum = 0.0; for(int i = 0; i < size; i++) { a[i] += 10; sum += a[i]; } return sum / size; // assume size > 0 } int main() { int arr[3] = {1, 2, 3}; double result = change(arr, 3); // Comment the above, and uncomment the below, to see // change only work on the 2nd and 3rd integers // double result = change(arr + 1, 2); printf("The array is now: "); for(int i = 0; i < 3; i++) { printf("%d ", arr[i]); } printf("\nAnd the average is %lf\n", result); return 0; }

63c6479f5f004bf4898cf545

2023-02-27T01:50:22.758Z

General Question

v1

So is it true that we only need to allocate space on the heap when variables with data that we want to persist throughout the program are created in the helper functions?

63c6479f5f004bf4898cf545

2023-02-28T05:54:04.047Z

Question from Code

v1

if car.color had pointed to &color_ptr instead, would it change to Blue?

struct Car car; char *color_ptr = "Green"; car.color = color_ptr; car.mileage = 1000; color_ptr = "Blue"; struct Car *car_ptr = &car;

63c6479f5f004bf4898cf545

2023-02-28T05:54:31.474Z

Question from Code

v1

is there a way to change car.color to blue

struct Car car; char *color_ptr = "Green"; car.color = color_ptr; car.mileage = 1000; color_ptr = "Blue"; struct Car *car_ptr = &car;

63c6479f5f004bf4898cf545

2023-03-02T01:56:23.981Z

Help Fix Code

v1

int main(int argc, char **argv) { if (argc != 2) { fprintf(stderr, "Usage: forkloop <iterations>\n"); exit(1); } int iterations = strtol (argv[1], NULL, 10); int is_parent = 0; for (int i = 0; i < iterations; i++) { if (is_parent == 0) { int n = fork(); if (n < 0) { perror("fork"); exit(1); } if (n == 0) { is_parent = 0; } } printf("ppid = %d, pid = %d, i = %d\n", getppid(), getpid(), i); } return 0; }

modify the program so that the new children do not create additional processes. Only the original parent calls fork. Keep the printf call for all processes. The resulting diagram will look something like the following when parentcreates 3 is run. In this case, the parent process creates 3 child processes. Note that the child process ids will not necessarily be in sequence.

63c6479f5f004bf4898cf545

2023-03-02T01:59:01.092Z

Help Fix Code

v1

int main(int argc, char **argv) { if (argc != 2) { fprintf(stderr, "Usage: forkloop <iterations>\n"); exit(1); } int iterations = strtol (argv[1], NULL, 10); int is_parent = 0; for (int i = 0; i < iterations; i++) { if (is_parent == 0) { int n = fork(); if (n < 0) { perror("fork"); exit(1); } if (n == 0) { is_parent = 1; } } printf("ppid = %d, pid = %d, i = %d\n", getppid(), getpid(), i); } return 0; }

modify the program so that the new children do not create additional processes. Only the original parent calls fork. Keep the printf call for all processes. The resulting diagram will look something like the following when parentcreates 3 is run. In this case, the parent process creates 3 child processes. Note that the child process ids will not necessarily be in sequence.

63c6479f5f004bf4898cf545

2023-03-02T03:08:06.741Z

Help Fix Code

v1

if (argc != 2) { fprintf(stderr, "Usage: forkloop <iterations>\n"); exit(1); } int iterations = strtol(argv[1], NULL, 10); for (int i = 0; i < iterations; i++) { if (getppid() == getpid()) { int n = fork(); if (n < 0) { perror("fork"); exit(1); } } printf("ppid = %d, pid = %d, i = %d\n", getppid(), getpid(), i); } return 0; }

Create a copy of forkloop.c called childcreates.c. In the new file, modify the program so that each process creates exactly one a new process. Keep the printf call for all processes.

63c6479f5f004bf4898cf545

2023-03-02T03:46:37.302Z

General Question

v1

how can i read a file line by line if i dont know the line length, only the max line length?

63c6479f5f004bf4898cf545

2023-03-03T00:23:53.799Z

Help Fix Code

v1

int main(int argc, char **argv) { if (argc != 2) { fprintf(stderr, "Usage: forkloop <iterations>\n"); exit(1); } int iterations = strtol(argv[1], NULL, 10); int child_count = 0; for (int i = 0; i < iterations; i++) { if (child_count == i) { int n = fork(); if (n < 0) { perror("fork"); exit(1); } else if (n == 0) { child_count++; } } printf("ppid = %d, pid = %d, i = %d\n", getppid(), getpid(), i); } return 0; }

each process creates exactly one new process

63c6479f5f004bf4898cf545

2023-03-09T22:15:40.372Z

Help Write Code

v2

Your task is to complete checkpasswd.c, which reads a user id and password from stdin, creates a new process to run the validate program, sends it the user id and password, and prints a message to stdout reporting whether the validation is successful.

63c6479f5f004bf4898cf545

2023-03-09T22:59:43.388Z

General Question

v2

how do you call wait

63c6479f5f004bf4898cf545

2023-03-09T23:07:44.392Z

General Question

v2

how do i perform write on a newline

63c6479f5f004bf4898cf545

2023-03-09T23:17:16.323Z

Question from Code

v2

how can i get rid of the error

write(fd[1], '\n', sizeof(char)); // Write the newline

63c6479f5f004bf4898cf545

2023-03-09T23:18:13.108Z

Question from Code

v2

how can i get rid of the error

execl("./validate", "validate", user_id, password);

63c6479f5f004bf4898cf545

2023-03-09T23:42:20.490Z

Question from Code

v2

why doesn't it properly check if the input is too long

if (write(fd[1], password, MAXLINE) == -1) { // Write the password perror("write to pipe"); } if ((close(fd[1])) == -1) { // Close the write perror("close"); } wait(&status); // wait if (WIFEXITED(status) && WEXITSTATUS(status) == 0) { // If it is equal to 0 printf(SUCCESS); } else { printf(INVALID); } } else if (r == 0) { // If child process if ((close(fd[1])) == -1) { // Close the write perror("close"); } if ((dup2(fd[0], fileno(stdin))) == -1) { // So it can read from pipe perror("dup2"); exit(1); } execl("./validate", "validate", user_id, password, NULL); // Validate } else { perror("fork"); // Check for failed fork exit(1); } return 0; } }

63c6479f5f004bf4898cf545

2023-03-09T23:44:45.464Z

Help Fix Code

v2

Your task is to complete checkpasswd.c, which reads a user id and password from stdin, creates a new process to run the validate program, sends it the user id and password, and prints a message to stdout reporting whether the validation is successful.

if (write(fd[1], password, MAXLINE) == -1) { // Write the password perror("write to pipe"); } if ((close(fd[1])) == -1) { // Close the write perror("close"); } wait(&status); // wait if (WIFEXITED(status) && WEXITSTATUS(status) == 0) { // If it is equal to 0 printf(SUCCESS); } else { printf(INVALID); } } else if (r == 0) { // If child process if ((close(fd[1])) == -1) { // Close the write perror("close"); } if ((dup2(fd[0], fileno(stdin))) == -1) { // So it can read from pipe perror("dup2"); exit(1); } execl("./validate", "validate", user_id, password, NULL); // Validate } else { perror("fork"); // Check for failed fork exit(1); } return 0; } }

63c6479f5f004bf4898cf545

2023-03-09T23:54:14.905Z

Question from Code

v2

would this code snippet correctly check for the status

wait(&status); // wait if (WIFEXITED(status) && WEXITSTATUS(status) == 0) { // If it is equal to 0 printf(SUCCESS); } else { printf(INVALID); }

63c6479f5f004bf4898cf545

2023-03-10T03:33:45.392Z

Question from Code

v2

what is wrong with my code

int main(void) { char user_id[MAXLINE]; char password[MAXLINE]; /* The user will type in a user name on one line followed by a password on the next. DO NOT add any prompts. The only output of this program will be one of the messages defined above. Please read the comments in validate carefully */ if(fgets(user_id, MAXLINE, stdin) == NULL) { perror("fgets"); exit(1); } if(fgets(password, MAXLINE, stdin) == NULL) { perror("fgets"); exit(1); } // Check for exceeded length if (strlen(user_id) > 10 || strlen(password) > 10) { printf(NO_USER); } else { int fd[2]; int r; // Create the pipe if ((pipe(fd) == -1)) { perror("pipe"); exit(1); } if ((r = fork()) > 0) { // If parent process int status; if ((close(fd[0])) == -1) { // Close the read perror("close"); } if (write(fd[1], user_id, strlen(user_id) + 1) == -1) { // Write the user id perror("write to pipe"); } write(fd[1], "\n", 1); // Write the newline if (write(fd[1], password, strlen(password) + 1) == -1) { // Write the password perror("write to pipe"); } if ((close(fd[1])) == -1) { // Close the write perror("close"); } wait(&status); // wait printf("%d", WEXITSTATUS(status)); if (WIFEXITED(status) && WEXITSTATUS(status) == 0) { // If it is equal to 0 printf(SUCCESS); } else { printf(INVALID); } } else if (r == 0) { // If child process if ((close(fd[1])) == -1) { // Close the write perror("close"); } if ((dup2(fd[0], fileno(stdin))) == -1) { // So it can read from pipe perror("dup2"); exit(1); } if ((close(fd[0])) == -1) { perror("close"); } execl("./validate", "validate", user_id, password, NULL); // Validate } else { perror("fork"); // Check for failed fork exit(1); } } return 0; }

63c6479f5f004bf4898cf545

2023-03-10T03:37:42.217Z

Help Write Code

v2

Your task is to complete checkpasswd.c, which reads a user id and password from stdin, creates a new process to run the validate program, sends it the user id and password, and prints a message to stdout reporting whether the validation is successful.

63c6479f5f004bf4898cf545

2023-03-10T13:24:07.689Z

Question from Code

v2

why do i get the wrong output

int main(void) { char user_id[MAXLINE]; char password[MAXLINE]; /* The user will type in a user name on one line followed by a password on the next. DO NOT add any prompts. The only output of this program will be one of the messages defined above. Please read the comments in validate carefully */ if(fgets(user_id, MAXLINE, stdin) == NULL) { perror("fgets"); exit(1); } if(fgets(password, MAXLINE, stdin) == NULL) { perror("fgets"); exit(1); } // Check for exceeded length if (strlen(user_id) > 10 || strlen(password) > 10) { printf(NO_USER); exit(0); } else { int fd[2]; int r; // Create the pipe if ((pipe(fd) == -1)) { perror("pipe"); exit(1); } if ((r = fork()) > 0) { // If parent process if ((close(fd[0])) == -1) { // Close the read perror("close"); } if (write(fd[1], user_id, MAXLINE) == -1) { // Write the user id perror("write to pipe"); } if (write(fd[1], password, MAXLINE) == -1) { // Write the password perror("write to pipe"); } if ((close(fd[1])) == -1) { // Close the write perror("close"); } int status; wait(&status); // wait if (WIFEXITED(status) && WEXITSTATUS(status) == 0) { // If it is equal to 0 printf(SUCCESS); } else if(WIFEXITED(status)) { printf(INVALID); } } else if (r == 0) { // If child process if ((close(fd[1])) == -1) { // Close the write perror("close"); } if (dup2(fd[0], fileno(stdin)) == -1) { // So it can read from pipe perror("dup2"); exit(1); } if ((close(fd[0])) == -1) { perror("close"); } execl("./validate", "validate", NULL); // Validate } else { perror("fork"); // Check for failed fork exit(1); } } return 0; }

63c6479f5f004bf4898cf545

2023-03-10T18:39:48.585Z

Question from Code

v2

is this right

if ((r = fork()) > 0) { // If parent process if ((close(fd[0])) == -1) { // Close the read perror("close"); } if (write(fd[1], user_id, MAXLINE) == -1) { // Write the user id perror("write to pipe"); } if (write(fd[1], password, MAXLINE) == -1) { // Write the password perror("write to pipe"); } if ((close(fd[1])) == -1) { // Close the write perror("close"); } int status; wait(&status); // wait if (WIFEXITED(status) && WEXITSTATUS(status) == 0) { // If it is equal to 0 printf(SUCCESS); } else if (WIFEXITED(status)) { printf(INVALID); }

63c6479f5f004bf4898cf545

2023-03-10T18:40:56.756Z

Question from Code

v2

why is user_id properly written to the pipe but password is not

if ((r = fork()) > 0) { // If parent process if ((close(fd[0])) == -1) { // Close the read perror("close"); } if (write(fd[1], user_id, MAXLINE) == -1) { // Write the user id perror("write to pipe"); } if (write(fd[1], password, MAXLINE) == -1) { // Write the password perror("write to pipe"); } if ((close(fd[1])) == -1) { // Close the write perror("close"); } int status; wait(&status); // wait if (WIFEXITED(status) && WEXITSTATUS(status) == 0) { // If it is equal to 0 printf(SUCCESS); } else if (WIFEXITED(status)) { printf(INVALID); }

63c6479f5f004bf4898cf545

2023-03-10T18:43:05.797Z

Question from Code

v2

would this code properly read 2 things that were written to it

} else if (r == 0) { // If child process if ((dup2(fd[0], fileno(stdin))) == -1) { // So it can read from pipe perror("dup2"); exit(1); } if ((close(fd[1])) == -1) { perror("close"); } if ((close(fd[0])) == -1) { perror("close"); } execl("./validate", "validate", NULL); // Validate } else { perror("fork"); // Check for failed fork exit(1); } }

63c6479f5f004bf4898cf545

2023-03-11T02:09:04.952Z

General Question

v2

how can i remove newline characters after calling fgets

63c6479f5f004bf4898cf545

2023-03-11T02:23:25.100Z

Question from Code

v2

are these functions correct

Rule *find_rule(char *target, Rule *head) { if (head == NULL) { // If linked list is empty, return NULL return NULL; } // Traverse the linked list Rule *curr = head; while ((curr != NULL) && (strcmp(curr->target, target) != 0)) { curr = curr->next_rule; } return curr; // Return curr if found, NULL if not found } Rule *create_rule(char *target) { Rule *new_rule = malloc(sizeof(Rule)); // Allocate space for a rule if (new_rule == NULL) { // Error checking perror("malloc"); exit(1); } strcpy(new_rule->target, target); // Set the target new_rule->next_rule = NULL; // Set the next_rule return new_rule; // Return the new rule }

63c6479f5f004bf4898cf545

2023-03-11T02:33:58.815Z

Question from Code

v2

why am i getting a segfault when create_rule is called

Rule *parse_file(FILE *fp) { char line[MAXLINE]; Rule *curr_rule = NULL; Rule *head_rule = NULL; int num_actions = 0; // Iterate through each line of the makefile while (fgets(line, sizeof(line), fp) != NULL) { // Process newline characters line[strcspn(line, "\r")] = '\0'; line[strcspn(line, "\n")] = '\0'; if ((line[0] != ' ') && (line[0] != '\t') && (line[0] != '#')) { // If is action line char *tok_line = strtok(line, " "); // Tokenize the line num_actions = 0; // Initialize the number of actions (back to) 0 if (find_rule(tok_line, head_rule) == NULL) { // If rule doesn't exist curr_rule = create_rule(tok_line); // Make a rule, set it to curr } else { curr_rule = find_rule(tok_line, head_rule); // Find the rule, set it to curr } while ((strcmp(tok_line, ":")) && (tok_line != NULL)) { // Iterate thru dependencies tok_line = strtok(NULL, " "); Dependency *new_dep = malloc(sizeof(Dependency)); // Dynamically allocate space for a dependency // Find or create a rule and assign it to the new dependency if (find_rule(tok_line, head_rule) == NULL) { new_dep->rule = create_rule(tok_line); } else { new_dep->rule = find_rule(tok_line, head_rule); } new_dep->next_dep = NULL; // Initialize next_dep to NULL // Add it to curr's list of dependencies if (curr_rule->dependencies == NULL) { curr_rule->dependencies = new_dep; } else { Dependency *curr_dep = curr_rule->dependencies; while (curr_dep->next_dep != NULL) { curr_dep = curr_dep->next_dep; } curr_dep->next_dep = new_dep; } } // Add the rule to the linked list if (head_rule == NULL) { head_rule = curr_rule; } else { Rule *curr = head_rule; while (curr->next_rule != NULL) { curr = curr->next_rule; } curr->next_rule = curr_rule; }

63c6479f5f004bf4898cf545

2023-03-11T02:47:58.704Z

Question from Code

v2

do you know if this code is properly ignoring blank lines in the file

while (fgets(line, sizeof(line), fp) != NULL) { // Process newline characters line[strcspn(line, "\r")] = '\0'; line[strcspn(line, "\n")] = '\0'; if ((line[0] != ' ') && (line[0] != '\t') && (line[0] != '#')) { // If is action line char *tok_line = strtok(line, " "); // Tokenize the line num_actions = 0; // Initialize the number of actions (back to) 0 if (find_rule(tok_line, head_rule) == NULL) { // If rule doesn't exist curr_rule = create_rule(tok_line); // Make a rule, set it to curr } else { curr_rule = find_rule(tok_line, head_rule); // Find the rule, set it to curr } while ((strcmp(tok_line, ":")) && (tok_line != NULL)) { // Iterate thru dependencies tok_line = strtok(NULL, " "); Dependency *new_dep = malloc(sizeof(Dependency)); // Dynamically allocate space for a dependency // Find or create a rule and assign it to the new dependency if (find_rule(tok_line, head_rule) == NULL) { new_dep->rule = create_rule(tok_line); } else { new_dep->rule = find_rule(tok_line, head_rule); } new_dep->next_dep = NULL; // Initialize next_dep to NULL // Add it to curr's list of dependencies if (curr_rule->dependencies == NULL) { curr_rule->dependencies = new_dep; } else { Dependency *curr_dep = curr_rule->dependencies;

63c6479f5f004bf4898cf545

2023-03-11T02:51:32.276Z

Question from Code

v2

why is there a segfault when this function is called by the program

Rule *create_rule(char *target) { Rule *new_rule = malloc(sizeof(Rule)); // Allocate space for a rule if (new_rule == NULL) { // Error checking perror("malloc"); exit(1); } strcpy(new_rule->target, target); // Set the target new_rule->next_rule = NULL; // Set the next_rule new_rule->dependencies = NULL; new_rule->actions = NULL; return new_rule; // Return the new rule }

63c6479f5f004bf4898cf545

2023-03-11T22:20:29.482Z

General Question

v2

what can i use to make a copy of a string

63c6479f5f004bf4898cf545

2023-03-11T22:26:51.969Z

Question from Code

v2

what does this code do

if (line[0] == '\0') { continue; }

63c6479f5f004bf4898cf545

2023-03-11T22:44:08.013Z

Help Write Code

v2

A rule is evaluated using the following steps: Update each of the dependencies. In other words, recursively evaluate each dependency rule. Compare the last modified time for each of the dependencies to the target. If the target does not exist, or at least one of the dependencies refers to a file with a last modified time more recent than the target, execute the rule's actions.

63c6479f5f004bf4898cf545

2023-03-11T22:44:32.635Z

Help Write Code

v2

A rule is evaluated using the following steps: Update each of the dependencies. In other words, recursively evaluate each dependency rule. Compare the last modified time for each of the dependencies to the target. If the target does not exist, or at least one of the dependencies refers to a file with a last modified time more recent than the target, execute the rule's actions.

63c6479f5f004bf4898cf545

2023-03-11T22:46:06.213Z

Help Write Code

v2

Update each of the dependencies. In other words, recursively evaluate each dependency rule. Compare the last modified time for each of the dependencies to the target. If the target does not exist, or at least one of the dependencies refers to a file with a last modified time more recent than the target, execute the rule's actions.

63c6479f5f004bf4898cf545

2023-03-12T02:25:35.461Z

General Question

v2

how do you use stat with examples

63c6479f5f004bf4898cf545

2023-03-12T03:24:44.549Z

General Question

v2

if im writing a make system, can i: -code a while loop to iterate through the dependencies and recursively call the program on them -after the while loop is finished, check if target exists. if not, execute the rule's' actions -if it does exist, create a struct using stat to hold the modification time of the target rule. loop through its dependencies and check for their modification times. if the modification time of the dependencies are more recent than the target, execute the action

63c6479f5f004bf4898cf545

2023-03-12T05:41:01.770Z

General Question

v2

how do you know if If the child terminates with a non-zero exit status

63c6479f5f004bf4898cf545

2023-03-12T05:42:09.250Z

General Question

v2

how do you know if If the child terminates with a non-zero exit status after using execvp

63c6479f5f004bf4898cf545

2023-03-12T05:46:02.561Z

General Question

v2

how do you print out multiple strings in an array into one line

63c6479f5f004bf4898cf545

2023-03-12T05:46:41.771Z

General Question

v2

how do i concatenate many strings together

63c6479f5f004bf4898cf545

2023-03-12T05:50:52.316Z

General Question

v2

how to initiliaze a string array

63c6479f5f004bf4898cf545

2023-03-12T16:24:58.742Z

General Question

v2

can you explain this to me: When pmake is run with the -p option, a child should be created to update each dependency. The parent will create one child process for each dependency and after it has created all of them, the parent will wait for all children to terminate successfully before determining whether it needs to execute the actions.

63c6479f5f004bf4898cf545

2023-03-12T16:33:19.272Z

General Question

v2

how do i check if a file/target exists

63c6479f5f004bf4898cf545

2023-03-12T16:42:02.341Z

Help Write Code

v2

When pmake is run with the -p option, a child should be created to update each dependency. The parent will create one child process for each dependency and after it has created all of them, the parent will wait for all children to terminate successfully before determining whether it needs to execute the actions.

63c6479f5f004bf4898cf545

2023-03-12T23:27:31.391Z

General Question

v2

can i do this to parallelize a makefile: 1. iterate through the dependencies, and at each dependency, fork the process. If its a child process, recursively call the program, then exit. if it is a parent, then wait. if so, what steps come next?

63c6479f5f004bf4898cf545

2023-03-12T23:41:16.560Z

Help Fix Code

v2

find the rule in the rules data structure corresponding to the target, and evaluate it. If target is NULL, then run_make will evaluate the first target in the rules list. this code will determine if the action of the rule in the makefile should be executed

Rule *curr = rule; while (curr->dependencies != NULL) { // Iterate through the linked list of dependencies run_make(curr->target, rules, 0); // Recursive call to run_make curr->dependencies = curr->dependencies->next_dep; } int execute = 1; // Create a variable to track if action should be executed // Check if target exists // access function suggested by Coding Assistant if (access(target, F_OK) != 0) { // If target does not exist execute = 0; // Update variable so action will be executed } else { struct stat rule_time; // Create a struct to hold the time if (stat(rule->target, rule_time) != 0) { // Error Checking perror("stat"); exit(1); } // Iterate through the dependencies Dependency *curr_dep = rule->dependencies; while (curr_dep != NULL) { struct stat dep_time; if (stat(curr_dep->rule->target, dep_time) != 0) { // Error Checking perror("stat"); exit(1); } if ((rule_time.st_mtim.tv_sec < dep_time.st_mtim.tvsec) // If dependency was modified more recently || ((rule_time.st_mtim.tv_sec == dep_time.st_mtim.tv_sec) && (rule_time.st_mtim.tv_nsec < rule_time.st_mtim.tv_nsec))) { execute = 0; // Update variable so action will be executed } } }

63c6479f5f004bf4898cf545

2023-03-13T19:24:18.956Z

Question from Code

v2

What does the program print to stderr if the user presses Ctrl+C at the moment when the program is at position B?

int x = 5; void handler(int sig) { x += 3; fprintf(stderr, "inside %d ", x); } int main() { fprintf(stderr, "start "); // POSITION A struct sigaction act; act.sa_handler = handler; act.sa_flags = 0; sigemptyset(&act.sa_mask); sigaction(SIGINT, &act, NULL); // POSITION B x += 2; // POSITION C fprintf(stderr, "outside %d", x); return 0; }

63c6479f5f004bf4898cf545

2023-03-13T20:28:12.118Z

General Question

v2

if im writing a program that executes makefiles, when executing multiple actions, do i need to loop through the actions and then fork once per action?

63c6479f5f004bf4898cf545

2023-03-14T03:33:58.092Z

Help Fix Code

v2

run make in parallel

Dependency *curr_dep = rule->dependencies; int num_dep = 0; while (curr_dep != NULL) { num_dep++; curr_dep = curr_dep->next_dep; } int child_pid_list[num_dep]; // Create a list to store the pid's of child processes int child_count = 0; // Create a variable to hold the number of children curr_dep = rule->dependencies; // Re-initialize curr_dep // Iterate through the dependencies and fork new processes for each while (curr_dep != NULL) { int pid = fork(); // Fork a new process if (pid > 0) { // If is parent process child_pid_list[child_count] = pid; // Add to the list of pids child_count++; } else if (pid == 0) { // If is child process run_make(curr_dep->rule->target, rules, 1); // Update the dependency exit(0); // Exit } else { // If fork fails perror("fork"); exit(1); } curr_dep = curr_dep->next_dep; } int status; // Check if all processes exited successfully for (int i = 0; i < child_count; i++) { waitpid(child_pid_list[i], &status, 0); if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) { // If non-zero exit status exit(1); } } execute = 0; // Update the variable so that the actions are executed }

63c6479f5f004bf4898cf545

2023-03-14T03:46:34.540Z

General Question

v2

how do i put a function prototype in another file

63c6479f5f004bf4898cf545

2023-03-14T03:47:42.406Z

General Question

v2

how do i put a function prototype in another file without a header file

63c6479f5f004bf4898cf545

2023-03-14T03:48:30.942Z

General Question

v2

how do i put a function prototype in another file without a header file and without extern

63c6479f5f004bf4898cf545

2023-03-14T03:48:31.209Z

General Question

v2

how do i put a function prototype in another file without a header file and without extern

63c6479f5f004bf4898cf545

2023-03-15T15:36:49.751Z

Question from Code

v2

does this parallelize make? Note that i later have a for loop that calls waitpid on the list of child_pids

if (rule == NULL) { // Base case for recursion return; } // Iterate through dependencies to get the number of dependencies if (rule->dependencies != NULL) { // Check if dependencies exist Dependency *curr_dep = rule->dependencies; int num_dep = 0; while (curr_dep != NULL) { num_dep++; curr_dep = curr_dep->next_dep; } int child_pid_list[num_dep]; // Create a list to store the pid's of child processes int child_count = 0; // Create a variable to hold the number of children curr_dep = rule->dependencies; // Re-initialize curr_dep // Iterate through the dependencies and fork new processes for each while (curr_dep != NULL) { int pid = fork(); // Fork a new process if (pid > 0) { // If is parent process child_pid_list[child_count] = pid; // Add to the list of pids child_count++; } else if (pid == 0) { // If is child process if ((access(rule->target, F_OK) != 0) || (dep_last_modified(rule, curr_dep) == 0)) { // If dependency was // last modified or non existent target run_make(curr_dep->rule->target, rules, 1); // Update the dependency exit(0); } exit(1); } else { // If fork fails perror("fork"); exit(1); } curr_dep = curr_dep->next_dep; } int status;

63c6479f5f004bf4898cf545

2023-03-15T15:39:18.064Z

Question from Code

v2

is this parallelizeing make?

if (rule == NULL) { // Base case for recursion return; } // Iterate through dependencies to get the number of dependencies if (rule->dependencies != NULL) { // Check if dependencies exist Dependency *curr_dep = rule->dependencies; int num_dep = 0; while (curr_dep != NULL) { num_dep++; curr_dep = curr_dep->next_dep; } int child_pid_list[num_dep]; // Create a list to store the pid's of child processes int child_count = 0; // Create a variable to hold the number of children curr_dep = rule->dependencies; // Re-initialize curr_dep // Iterate through the dependencies and fork new processes for each while (curr_dep != NULL) { int pid = fork(); // Fork a new process if (pid > 0) { // If is parent process child_pid_list[child_count] = pid; // Add to the list of pids child_count++; } else if (pid == 0) { // If is child process if ((access(rule->target, F_OK) != 0) || (dep_last_modified(rule, curr_dep) == 0)) { // If dependency was // last modified or non existent target run_make(curr_dep->rule->target, rules, 1); // Update the dependency exit(0); } exit(1); } else { // If fork fails perror("fork"); exit(1); } curr_dep = curr_dep->next_dep; } int status; for (int i = 0; i < child_count; i++) { waitpid(child_pid_list[i], &status, 0); if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) { // If non-zero exit status exit(1); } execute = 0; // Signal to execute. If any if statements do fail, the program would have exited }

63c6479f5f004bf4898cf545

2023-03-17T13:28:09.856Z

General Question

v2

how do you use sigaction to handle sigprofs

63c6479f5f004bf4898cf545

2023-03-22T18:28:30.044Z

General Question

v2

what does updating inbuf mean

63c6479f5f004bf4898cf545

2023-03-23T21:14:19.117Z

General Question

v2

what do i need to do here: / You want to move the stuff after the full line to the beginning // of the buffer. A loop can do it, or you can use memmove. // memmove(destination, source, number_of_bytes)

63c6479f5f004bf4898cf545

2023-03-23T21:27:07.701Z

Question from Code

v2

is this right so far?

while ((nbytes = read(fd, after, room)) > 0) { // Step 1: update inbuf (how many bytes were just added?) inbuf = nbytes; int where; // Step 2: the loop condition below calls find_network_newline // to determine if a full line has been read from the client. // Your next task should be to implement find_network_newline // (found at the bottom of this file). // // Note: we use a loop here because a single read might result in // more than one full line. while ((where = find_network_newline(buf, inbuf)) > 0) { // where is now the index into buf immediately after // the first network newline // Step 3: Okay, we have a full line. // Output the full line, not including the "\r\n", // using print statement below. // Be sure to put a '\0' in the correct place first; // otherwise you'll get junk in the output. buf[where - 2] = '\0'; printf("Next message: %s\n", buf); // Note that we could have also used write to avoid having to // put the '\0' in the buffer. Try using write later! // Step 4: update inbuf and remove the full line from the buffer // There might be stuff after the line, so don't just do inbuf = 0. // You want to move the stuff after the full line to the beginning // of the buffer. A loop can do it, or you can use memmove. // memmove(destination, source, number_of_bytes) inbuf -= where; memmove(buf, inbuf, sizeof(buf) - sizeof(inbuf)); }

63c6479f5f004bf4898cf545

2023-03-23T22:00:30.161Z

Question from Code

v2

is this good?

int main() { // This line causes stdout not to be buffered. // Don't change this! Necessary for autotesting. setbuf(stdout, NULL); struct sockaddr_in *self = init_server_addr(PORT); int listenfd = set_up_server_socket(self, 5); while (1) { int fd = accept_connection(listenfd); if (fd < 0) { continue; } // Receive messages char buf[BUFSIZE] = {'\0'}; int inbuf = 0; // How many bytes currently in buffer? int room = sizeof(buf); // How many bytes remaining in buffer? char *after = buf; // Pointer to position after the data in buf int nbytes; while ((nbytes = read(fd, after, room)) > 0) { // Step 1: update inbuf (how many bytes were just added?) inbuf = nbytes; int where; // Step 2: the loop condition below calls find_network_newline // to determine if a full line has been read from the client. // Your next task should be to implement find_network_newline // (found at the bottom of this file). // // Note: we use a loop here because a single read might result in // more than one full line. while ((where = find_network_newline(buf, inbuf)) > 0) { buf[where - 2] = '\0'; printf("Next message: %s\n", buf); inbuf -= where; memmove(buf, buf + where, sizeof(buf) - where); } // Step 5: update after and room, in preparation for the next read. after = buf; room = sizeof(buf) - find_network_newline(buf, inbuf); } close(fd); printf("The connection is now closed ...\n"); } free(self); close(listenfd); return 0; } int find_network_newline(const char *buf, int n) { for (int i = 0; i < n - 1; i++) { if ((buf[i] == '\r') && (buf[i + 1] == '\n')) { return i + 2; } } return -1; }

63c6479f5f004bf4898cf545

2023-03-23T22:25:13.783Z

Question from Code

v2

did i correctly update inbuf to the correct value

char buf[BUFSIZE] = {'\0'}; int inbuf = 0; // How many bytes currently in buffer? int room = sizeof(buf); // How many bytes remaining in buffer? char *after = buf; // Pointer to position after the data in buf int nbytes; while ((nbytes = read(fd, after, room)) > 0) { // Step 1: update inbuf (how many bytes were just added?) inbuf = nbytes; int where;

63c6479f5f004bf4898cf545

2023-03-23T22:26:01.204Z

Question from Code

v2

is the correct message being printed

while ((where = find_network_newline(buf, inbuf)) > 0) { // where is now the index into buf immediately after // the first network newline // Step 3: Okay, we have a full line. // Output the full line, not including the "\r\n", // using print statement below. // Be sure to put a '\0' in the correct place first; // otherwise you'll get junk in the output. buf[where - 2] = '\0'; printf("Next message: %s\n", buf);

63c6479f5f004bf4898cf545

2023-03-23T22:27:57.541Z

Question from Code

v2

is the stuff after the full line moved to the beginning of the buffer and is after and room being correctly updated

// Note that we could have also used write to avoid having to // put the '\0' in the buffer. Try using write later! // Step 4: update inbuf and remove the full line from the buffer // There might be stuff after the line, so don't just do inbuf = 0. // You want to move the stuff after the full line to the beginning // of the buffer. A loop can do it, or you can use memmove. // memmove(destination, source, number_of_bytes) inbuf -= where; memmove(buf, buf + where, sizeof(buf) - where); } // Step 5: update after and room, in preparation for the next read. after = buf; room = sizeof(buf) - find_network_newline(buf, inbuf); } close(fd); printf("The connection is now closed ...\n"); } free(self); close(listenfd); return 0; }

63c6479f5f004bf4898cf545

2023-03-23T22:58:31.677Z

Help Fix Code

v2

you have a buffer (a character array) where you store pieces of a message until you have a network newline ("\r\n"). Each message piece goes after the data that you've already placed in the buffer. When you find a network newline, you know that you have a complete message, so you can print that message and then shift any remaining bytes to the front of the buffer as the start of the next copy of the message.

int main() { // This line causes stdout not to be buffered. // Don't change this! Necessary for autotesting. setbuf(stdout, NULL); struct sockaddr_in *self = init_server_addr(PORT); int listenfd = set_up_server_socket(self, 5); while (1) { int fd = accept_connection(listenfd); if (fd < 0) { continue; } // Receive messages char buf[BUFSIZE] = {'\1'}; int inbuf = 0; // How many bytes currently in buffer? int room = sizeof(buf); // How many bytes remaining in buffer? char *after = buf; // Pointer to position after the data in buf int nbytes; while ((nbytes = read(fd, after, room)) > 0) { // Step 1: update inbuf (how many bytes were just added?) inbuf = nbytes; int where; while ((where = find_network_newline(buf, inbuf)) > 0) { // where is now the index into buf immediately after // the first network newline buf[where + 2] = '\0'; printf("Next message: %s\n", buf); // Step 4: update inbuf and remove the full line from the buffer // There might be stuff after the line, so don't just do inbuf = 0. inbuf -= where; memmove(buf, buf + where, sizeof(where) + 1); } // Step 5: update after and room, in preparation for the next read. after = buf; room = BUFSIZE - inbuf; } close(fd); printf("The connection is now closed ...\n"); } free(self); close(listenfd); return 0; } /* * Search the first n characters of buf for a network newline (\r\n). * Return one plus the index of the '\n' of the first network newline, * or -1 if no network newline is found. The return value is the index into buf * where the current line ends. * */ int find_network_newline(const char *buf, int n) { for (int i = 0; i < n - 1; i++) { if ((buf[i] == '\r') && (buf[i + 1] == '\n')) { return i + 2; } } return -1; }

63c6479f5f004bf4898cf545

2023-03-23T22:59:51.752Z

Question from Code

v2

why arent i getting the right output

int main() { // This line causes stdout not to be buffered. // Don't change this! Necessary for autotesting. setbuf(stdout, NULL); struct sockaddr_in *self = init_server_addr(PORT); int listenfd = set_up_server_socket(self, 5); while (1) { int fd = accept_connection(listenfd); if (fd < 0) { continue; } // Receive messages char buf[BUFSIZE] = {'\1'}; int inbuf = 0; // How many bytes currently in buffer? int room = sizeof(buf); // How many bytes remaining in buffer? char *after = buf; // Pointer to position after the data in buf int nbytes; while ((nbytes = read(fd, after, room)) > 0) { // Step 1: update inbuf (how many bytes were just added?) inbuf = nbytes; int where; while ((where = find_network_newline(buf, inbuf)) > 0) { // where is now the index into buf immediately after // the first network newline buf[where + 2] = '\0'; printf("Next message: %s\n", buf); // Step 4: update inbuf and remove the full line from the buffer // There might be stuff after the line, so don't just do inbuf = 0. inbuf -= where; memmove(buf, buf + where, sizeof(where) + 1); } // Step 5: update after and room, in preparation for the next read. after = buf; room = BUFSIZE - inbuf; } close(fd); printf("The connection is now closed ...\n"); } free(self); close(listenfd); return 0; } int find_network_newline(const char *buf, int n) { for (int i = 0; i < n - 1; i++) { if ((buf[i] == '\r') && (buf[i + 1] == '\n')) { return i + 2; } } return -1; }

63c6479f5f004bf4898cf545

2023-03-23T23:32:14.616Z

Question from Code

v2

which line or lines are giving me the undesired output

int main() { // This line causes stdout not to be buffered. // Don't change this! Necessary for autotesting. setbuf(stdout, NULL); struct sockaddr_in *self = init_server_addr(PORT); int listenfd = set_up_server_socket(self, 5); while (1) { int fd = accept_connection(listenfd); if (fd < 0) { continue; } // Receive messages char buf[BUFSIZE] = {'\1'}; int inbuf = 0; // How many bytes currently in buffer? int room = sizeof(buf); // How many bytes remaining in buffer? char *after = buf; // Pointer to position after the data in buf int nbytes; while ((nbytes = read(fd, after, room)) > 0) { // Step 1: update inbuf (how many bytes were just added?) inbuf += nbytes; int where; // Step 2: the loop condition below calls find_network_newline // to determine if a full line has been read from the client. // Your next task should be to implement find_network_newline // (found at the bottom of this file). // // Note: we use a loop here because a single read might result in // more than one full line. while ((where = find_network_newline(buf, inbuf)) > 0) { // where is now the index into buf immediately after // the first network newline // Step 3: Okay, we have a full line. // Output the full line, not including the "\r\n", // using print statement below. // Be sure to put a '\0' in the correct place first; buf[where - 2] = '\0'; printf("Next message: %s\n", buf); inbuf -= where; ; memmove(buf, buf + where + 1, inbuf); } // Step 5: update after and room, in preparation for the next read. after = buf; room = sizeof(buf) - inbuf; } close(fd); printf("The connection is now closed ...\n"); } free(self); close(listenfd); return 0; } int find_network_newline(const char *buf, int n) { for (int i = 0; i < n - 1; i++) { if ((buf[i] == '\r') && (buf[i + 1] == '\n')) { return i + 2; } } return -1; }

63c6479f5f004bf4898cf545

2023-03-31T21:17:36.028Z

General Question

v2

how do i do this: Change the code to broadcast to all connected clients