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like 2

63c648c65f004bf4898cff95

2023-01-25T23:46:24.618Z

Help Fix Code

v1

void fib(int **sequence, int n) { *sequence = malloc(sizeof(int) * n); *sequence[0] = 0; if (n > 1) { *sequence[1] = 1; for (int i = 2; i < n; i++) { *sequence[i] = *sequence[i - 2] + *sequence[i - 1]; } } } int main(int argc, char **argv) { /* do not change this main function */ int count = strtol(argv[1], NULL, 10); int *fib_sequence; fib(&fib_sequence, count); for (int i = 0; i < count; i++) { printf("%d ", fib_sequence[i]); } free(fib_sequence); return 0; }

no segmentation fault

63c648c65f004bf4898cff95

2023-01-26T17:02:08.983Z

General Question

v1

does scanf take in one line of input at a time?

63c648c65f004bf4898cff95

2023-01-26T17:02:51.552Z

General Question

v1

if there are multiple lines of input, do I need multiple scanf calls, one for each line?

63c648c65f004bf4898cff95

2023-01-28T02:27:24.174Z

Question from Code

v1

why does this code produce a bus error?

int check_permissions(char *file_perm, char *min_perm) { for (int i = 0; i < 9; i++) { if(file_perm[i] == '-' && min_perm[i] != '-') { return 1; } } return 0; } int main(int argc, char** argv) { if (!(argc == 2 || argc == 3)) { fprintf(stderr, "USAGE: count_large size [permissions]\n"); return 1; } // TODO: Process command line arguments. int min_size = strtol(argv[1], NULL, 10); char *min_permission; if (argc == 3) { min_permission = argv[2]; } scanf("%*s"); //the first line of input from ls -l, to be discarded int count = 0; //the number of files large enough and have the right permission char* file_size; //the size of the file read by scanf char* file_permission; //permission field of a file while (scanf("%*c%s %*s %*s %*s %s %*s %*s %*s %*s",file_permission, file_size) != EOF) { if (strtol(file_size, NULL, 10) >= min_size) { //checks if file is large enough if (argc == 2) { count++; } if (argc == 3){ if(check_permissions(file_permission, min_permission) == 0) { count++; } } } } // TODO: Call check_permissions as part of your solution to count the files to // compute and print the correct value. printf("%d\n",count); return 0; }

63c648c65f004bf4898cff95

2023-01-28T02:28:26.834Z

Question from Code

v1

why does this code produce a bus error when run from the terminal?

int check_permissions(char *file_perm, char *min_perm) { for (int i = 0; i < 9; i++) { if(file_perm[i] == '-' && min_perm[i] != '-') { return 1; } } return 0; } int main(int argc, char** argv) { if (!(argc == 2 || argc == 3)) { fprintf(stderr, "USAGE: count_large size [permissions]\n"); return 1; } // TODO: Process command line arguments. int min_size = strtol(argv[1], NULL, 10); char *min_permission; if (argc == 3) { min_permission = argv[2]; } scanf("%*s"); //the first line of input from ls -l, to be discarded int count = 0; //the number of files large enough and have the right permission char* file_size; //the size of the file read by scanf char* file_permission; //permission field of a file while (scanf("%*c%s %*s %*s %*s %s %*s %*s %*s %*s",file_permission, file_size) != EOF) { if (strtol(file_size, NULL, 10) >= min_size) { //checks if file is large enough if (argc == 2) { count++; } if (argc == 3){ if(check_permissions(file_permission, min_permission) == 0) { count++; } } } } // TODO: Call check_permissions as part of your solution to count the files to // compute and print the correct value. printf("%d\n",count); return 0; }

63c648c65f004bf4898cff95

2023-01-28T02:29:21.548Z

Help Fix Code

v1

int check_permissions(char *file_perm, char *min_perm) { for (int i = 0; i < 9; i++) { if(file_perm[i] == '-' && min_perm[i] != '-') { return 1; } } return 0; } int main(int argc, char** argv) { if (!(argc == 2 || argc == 3)) { fprintf(stderr, "USAGE: count_large size [permissions]\n"); return 1; } // TODO: Process command line arguments. int min_size = strtol(argv[1], NULL, 10); char *min_permission; if (argc == 3) { min_permission = argv[2]; } scanf("%*s"); //the first line of input from ls -l, to be discarded int count = 0; //the number of files large enough and have the right permission char* file_size; //the size of the file read by scanf char* file_permission; //permission field of a file while (scanf("%*c%s %*s %*s %*s %s %*s %*s %*s %*s",file_permission, file_size) != EOF) { if (strtol(file_size, NULL, 10) >= min_size) { //checks if file is large enough if (argc == 2) { count++; } if (argc == 3){ if(check_permissions(file_permission, min_permission) == 0) { count++; } } } } // TODO: Call check_permissions as part of your solution to count the files to // compute and print the correct value. printf("%d\n",count); return 0; }

no bus error

63c648c65f004bf4898cff95

2023-01-28T02:32:42.283Z

Question from Code

v1

why is the value of count always 0 at the end?

#include <stdio.h> #include <stdlib.h> // TODO: Implement a helper named check_permissions that matches the prototype below. int check_permissions(char *file_perm, char *min_perm) { for (int i = 0; i < 9; i++) { if(file_perm[i] == '-' && min_perm[i] != '-') { return 1; } } return 0; } int main(int argc, char** argv) { if (!(argc == 2 || argc == 3)) { fprintf(stderr, "USAGE: count_large size [permissions]\n"); return 1; } // TODO: Process command line arguments. int min_size = strtol(argv[1], NULL, 10); char *min_permission; if (argc == 3) { min_permission = argv[2]; } scanf("%*s"); //the first line of input from ls -l, to be discarded int count = 0; //the number of files large enough and have the right permission char* file_size = malloc(sizeof(long)); //the size of the file read by scanf char* file_permission = malloc(sizeof(char) * 9); //permission field of a file while (scanf("%*c%s %*s %*s %*s %s %*s %*s %*s %*s",file_permission, file_size) != EOF) { if (strtol(file_size, NULL, 10) >= min_size) { //checks if file is large enough if (argc == 2) { count++; } if (argc == 3){ if(check_permissions(file_permission, min_permission) == 0) { count++; } } } } // TODO: Call check_permissions as part of your solution to count the files to // compute and print the correct value. printf("%d\n",count); return 0; }

63c648c65f004bf4898cff95

2023-01-29T03:33:19.365Z

Question from Code

v1

why does the scarf call not skip the first character in the line of input read?

char* file_size = malloc(sizeof(char) * 31); //the size of the file read by scanf char* file_permission = malloc(sizeof(char) * 31); //permission field of a file scanf("%*c%*c%s %*s %*s %*s %s %*s %*s %*s %*s",file_permission, file_size)

63c648c65f004bf4898cff95

2023-01-29T03:33:52.034Z

Question from Code

v1

why does the scarf call not skip the first character in the line of input read?

char* file_size = malloc(sizeof(char) * 31); //the size of the file read by scanf char* file_permission = malloc(sizeof(char) * 31); //permission field of a file scanf("%*c%s %*s %*s %*s %s %*s %*s %*s %*s",file_permission, file_size)

63c648c65f004bf4898cff95

2023-01-29T03:34:34.185Z

Help Fix Code

v1

char* file_size = malloc(sizeof(char) * 31); //the size of the file read by scanf char* file_permission = malloc(sizeof(char) * 31); //permission field of a file scanf("%*c%s %*s %*s %*s %s %*s %*s %*s %*s",file_permission, file_size)

scanf skips the first character of the line of input

63c648c65f004bf4898cff95

2023-02-12T21:42:06.925Z

General Question

v1

how to display ascii file in terminal in C?

63c648c65f004bf4898cff95

2023-02-14T02:42:41.431Z

General Question

v1

suppose we have the following line at the top of our program #define MAXNAME = 32; and then the declaration char name[MAXNAME]; in the program. What will this declaration line become after the program has passed through the C pre-processor?

63c648c65f004bf4898cff95

2023-02-17T07:02:38.381Z

Question from Code

v1

why does this code produce a bus error?

#include <stdio.h> #include <string.h> int main() { char* dest = "123456789"; char* src = "abc"; strncpy(dest, src, 5); printf("%s\n", dest); return 0; }

63c648c75f004bf4898cff9f

2023-01-24T03:13:23.598Z

Help Fix Code

v1

#include <stdio.h> #include <stdlib.h> int **split_array(const int *s, int length) { int num_even_indices; if (length % 2 == 0) { num_even_indices = length / 2; } else { num_even_indices = (length / 2) + 1; } int **arr = malloc(2 * sizeof(int*)); arr[0] = malloc(num_even_indices * sizeof(int)); // Array for even indices arr[1] = malloc((length - num_even_indices) * sizeof(int)); // Array for odd indices int even_index; int odd_index; for (int i = 0; i < length; i++) { if (i % 2 == 0) { arr[0][even_index] = s[i]; even_index += 1; } else { arr[1][odd_index] = s[i]; odd_index += 1; } } return arr; } /* Return a pointer to an array of ints with size elements. - strs is an array of strings where each element is the string representation of an integer. - size is the size of the array */ int *build_array(char **strs, int size) { int *arr = malloc(size * sizeof(int)); for (int i = 0; i < size; i++) { // Starting at i = 1 because argv[0] is not used. arr[i] = strtol(strs[i + 1], NULL, 10); } return arr; } int main(int argc, char **argv) { /* Replace the comments in the next two lines with the appropriate arguments. Do not add any additional lines of code to the main function or make other changes. */ int *full_array = build_array(argv, argc - 1); int **result = split_array(full_array, argc - 1); // Length of full_array is argc - 1 because it does not include argv[0]. printf("Original array:\n"); for (int i = 0; i < argc - 1; i++) { printf("%d ", full_array[i]); } printf("\n"); printf("result[0]:\n"); for (int i = 0; i < argc / 2; i++) { printf("%d ", result[0][i]); } printf("\n"); printf("result[1]:\n"); for (int i = 0; i < (argc - 1) / 2; i++) { printf("%d ", result[1][i]); } printf("\n"); free(full_array); free(result[0]); free(result[1]); free(result); return 0; }

Split input array into two arrays. The first array contains the elements of the input array that are at even indices. The second array contains the elements of the input array s that are at odd indices. Print the arrays.

63c648c75f004bf4898cff9f

2023-01-25T13:38:16.033Z

Help Fix Code

v1

#include <stdio.h> #include <string.h> #include <stdlib.h> struct contact { char name[30]; int phone_number; char address[30]; }; void update_contact(struct contact *friend, char *name, int number, char *address) { strcpy((*friend).name, *name); (*friend).phone_number = number; strcpy((*friend).address, *address); } int main(int argc, char **argv) { struct contact friend; // set initial values for friend strcpy(friend.name, "Jane Doe"); friend.phone_number = 377177377; strcpy(friend.address, "3771 University Avenue"); char *name; int number; char *address; // in hidden code set values for these 3 variables // call update_contact to change the values in friend update_contact(&friend, name, number, address); return 0; }

update the struct contact friend

63c648c75f004bf4898cff9f

2023-01-25T13:49:50.203Z

Help Fix Code

v1

struct Node { int value; struct Node *next; };

create node struct

63c648c75f004bf4898cff9f

2023-01-25T13:50:34.878Z

Help Fix Code

v1

struct Node { int value; struct node *next; };

create a node struct

63c648c75f004bf4898cff9f

2023-01-25T14:38:29.220Z

Help Fix Code

v1

typedef struct node { int value; struct node *next; } Node; int main() { Node *front; Node *curr = front; while ((*curr).next != NULL) { printf("%d ", (*curr).value); curr = (*curr).next; } printf("%d ", (*curr).value); return 0; }

traverse and print the whole linked list

63c648c75f004bf4898cff9f

2023-01-25T14:41:10.705Z

Explain Code

v1

typedef struct node { int value; struct node *next; } Node; int main() { Node *front; Node *curr = front; while ((*curr).next != NULL) { printf("%d ", (*curr).value); curr = (*curr).next; } printf("%d ", (*curr).value); return 0; }

63c648c75f004bf4898cff9f

2023-02-06T22:33:29.781Z

Help Fix Code

v1

int make_post(const User *author, User *target, char *contents) { if (author == NULL || target == NULL) { // Check if either User pointer is NULL return 2; } int i = 0; while (i < MAX_FRIENDS && author->friends[i] != NULL && author->friends[i] != target) { // Traverse through the author's friends; friendship is symmetrical so we don't need to do the same for target i++; } if ((i == MAX_FRIENDS && author->friends[i - 1] != target) || author->friends[i] == NULL) { // Check if users exist but are not friends return 1; } // We can create the post Post *new_post = malloc(sizeof(Post)); strcpy(new_post->author, author->name); //new_post->contents = malloc(sizeof(strlen(contents))); //strcpy(new_post->contents, contents); // *(new_post->date) = time(NULL); if (target->first_post == NULL) { target->first_post = new_post; } else { new_post->next = target->first_post; target->first_post = new_post; } return 0; }

linked list

63c648c75f004bf4898cff9f

2023-02-06T22:35:14.084Z

Help Fix Code

v1

int make_post(const User *author, User *target, char *contents) { if (author == NULL || target == NULL) { // Check if either User pointer is NULL return 2; } int i = 0; while (i < MAX_FRIENDS && author->friends[i] != NULL && author->friends[i] != target) { // Traverse through the author's friends; friendship is symmetrical so we don't need to do the same for target i++; } if ((i == MAX_FRIENDS && author->friends[i - 1] != target) || author->friends[i] == NULL) { // Check if users exist but are not friends return 1; } // We can create the post Post *new_post = malloc(sizeof(Post)); strcpy(new_post->author, author->name); new_post->contents = malloc(sizeof(strlen(contents))); strcpy(new_post->contents, contents); *(new_post->date) = time(NULL); if (target->first_post == NULL) { target->first_post = new_post; } else { new_post->next = target->first_post; target->first_post = new_post; } return 0; }

linked list

63c648c75f004bf4898cff9f

2023-02-06T22:37:23.107Z

Help Fix Code

v1

int make_post(const User *author, User *target, char *contents) { if (author == NULL || target == NULL) { // Check if either User pointer is NULL return 2; } int i = 0; while (i < MAX_FRIENDS && author->friends[i] != NULL && author->friends[i] != target) { // Traverse through the author's friends; friendship is symmetrical so we don't need to do the same for target i++; } if ((i == MAX_FRIENDS && author->friends[i - 1] != target) || author->friends[i] == NULL) { // Check if users exist but are not friends return 1; } // We can create the post Post *new_post = malloc(sizeof(Post)); strcpy(new_post->author, author->name); new_post->contents = malloc(sizeof(strlen(contents))); strcpy(new_post->contents, contents); new_post->date = time(NULL); if (target->first_post == NULL) { target->first_post = new_post; } else { new_post->next = target->first_post; target->first_post = new_post; } return 0; }

linked list

63c648c75f004bf4898cff9f

2023-02-06T23:25:02.865Z

Help Fix Code

v1

printf("Posts:\n"); Post *curr = user->first_post; while (curr != NULL) { printf("From: %s\n", curr->author); printf("Date: %s\n\n", ctime(curr->date)); printf("%s", curr->contents); curr = curr->next; if (curr != NULL) { printf("===\n\n"); } }

print

63c648c75f004bf4898cff9f

2023-02-07T14:37:51.590Z

Help Fix Code

v1

User *curr_del = *user_ptr_del; // Edge case: user to be deleted is first in user list if (strcmp(name, curr_del->name) == 0) { *user_ptr_del = curr_del->next; } while ((curr_del->next != NULL) && (strcmp(name, curr_del->next->name) != 0)) { curr_del = curr_del->next; } if ((curr_del->next != NULL) && (strcmp(name, curr_del->next->name) == 0)) { // Normal case: user is not at the beginning or end of the user list curr_del->next = curr_del->next->next; curr_del->next->next = NULL; } else { // Edge case: user is at the end of the user list curr_del->next = NULL; } free(find_user(name, *user_ptr_del)); return 0;

delete user

63c648c75f004bf4898cff9f

2023-02-07T14:40:36.932Z

Help Fix Code

v1

int delete_user(const char *name, User **user_ptr_del) { if (find_user(name, *user_ptr_del) == NULL) { // Check if a user with this name does not exist return 1; } int index = 0; User *curr = *user_ptr_del; while (curr != NULL) { // Traverse through every user in the user list index = find_friend(curr->friends, name); for (int i = index; i < MAX_FRIENDS; i++) { // Find the friend and delete them + "shift" the friend list elements accordingly // for EACH user if ((i == MAX_FRIENDS - 1) && (curr->friends[MAX_FRIENDS - 1] != NULL)) { // Edge case: when the friend to delete is at the end of the list curr->friends[i] = NULL; } else if (curr->friends[i] == NULL) { break; } else { // Technique for "shifting" elements: delete the user at the current index by // overwriting with the user at the next index curr->friends[i] = curr->friends[i + 1]; } } curr = curr->next; } // Deleting the user User *curr_del = *user_ptr_del; // Edge case: user to be deleted is first in user list if (strcmp(name, curr_del->name) == 0) { *user_ptr_del = curr_del->next; } while ((curr_del->next != NULL) && (strcmp(name, curr_del->next->name) != 0)) { curr_del = curr_del->next; } if ((curr_del->next != NULL) && (strcmp(name, curr_del->next->name) == 0)) { // Normal case: user is not at the beginning or end of the user list curr_del->next = curr_del->next->next; curr_del->next->next = NULL; } else { // Edge case: user is at the end of the user list curr_del->next = NULL; } free(find_user(name, *user_ptr_del)); return 0; }

delete user

63c648c75f004bf4898cff9f

2023-02-23T03:28:09.154Z

Help Fix Code

v1

Rule *parse_file(FILE *fp) { Rule *head = malloc(sizeof(Rule)); Rule *curr_rule = head; char *line[MAXLINE + 1]; // the +1 accounts for a null terminator from fgets while (fgets(*line, MAXLINE + 1, fp) != NULL) { // if the line is not a comment or empty: if (is_comment_or_empty((const char *) line) == 0) { // if the line is an action: if (strcmp(line[0], " ") == 0) { // CREATE THE ACTIONS // 1. Initialize the args array int size_of_args_arr = size_of_arr(*line + sizeof('\t')); // char *const argv[size_of_args_arr + 1]; // +1 accounts for NULL pointer at end Action *curr_action; // 2. Fill the args array if (head->actions == NULL) { head->actions = malloc(sizeof(Action)); head->actions->args = malloc(sizeof(char *const) * (size_of_args_arr + 1)); fill_args_arr(size_of_args_arr, *line, head->actions->args); curr_action = head->actions; } else { Action *new_action = malloc(sizeof(Action)); new_action->args = malloc(sizeof(char *const) * (size_of_args_arr + 1)); fill_args_arr(size_of_args_arr, *line, new_action->args); curr_action->next_act = new_action; curr_action = new_action; } } // else the line consists of the target // CREATE THE TARGET char *target = find_target(*line); if (head == NULL) { head->target = target; } else { Rule *new_rule = malloc(sizeof(Rule)); new_rule->target = target; curr_rule->next_rule = new_rule; curr_rule = new_rule; } } } }

create linked list

63c648c75f004bf4898cffa4

2023-01-19T07:04:08.480Z

General Question

v1

What is a pointer?

63c648c75f004bf4898cffa4

2023-01-19T07:11:07.589Z

General Question

v1

What does the scanf function do?

63c648c75f004bf4898cffa4

2023-01-19T07:12:19.429Z

General Question

v1

Provide an example of the scanf function in code.

63c648c75f004bf4898cffa4

2023-01-20T00:18:25.926Z

Question from Code

v1

What are argc and argv?

int main(int argc, char **argv) { int size = argc - 1; int *score_card[size]; for (int i = 0; i < size; i++) { // NOTE: We haven't covered malloc yet, so don't worry about this line. score_card[i] = malloc(sizeof(int)); *(score_card[i]) = strtol(argv[i + 1], NULL, 10); } printf("Sum: %d\n", sum_card(score_card, size)); return 0; }

63c648c75f004bf4898cffa4

2023-01-20T00:20:19.121Z

Question from Code

v1

What does line 8 do?

int main(int argc, char **argv) { int size = argc - 1; int *score_card[size]; for (int i = 0; i < size; i++) { // NOTE: We haven't covered malloc yet, so don't worry about this line. score_card[i] = malloc(sizeof(int)); *(score_card[i]) = strtol(argv[i + 1], NULL, 10); } printf("Sum: %d\n", sum_card(score_card, size)); return 0; }

63c648c75f004bf4898cffa4

2023-01-20T00:21:34.879Z

Explain Code

v1

int main(int argc, char **argv) { int size = argc - 1; int *score_card[size]; for (int i = 0; i < size; i++) { // NOTE: We haven't covered malloc yet, so don't worry about this line. score_card[i] = malloc(sizeof(int)); *(score_card[i]) = strtol(argv[i + 1], NULL, 10); } printf("Sum: %d\n", sum_card(score_card, size)); return 0; }

63c648c75f004bf4898cffa4

2023-01-20T00:23:44.281Z

General Question

v1

What is the strtol function?

63c648c75f004bf4898cffa4

2023-01-28T09:29:40.063Z

General Question

v1

How do I redirect the contents of a text file into standard input?

63c648c75f004bf4898cffa4

2023-01-28T09:39:22.744Z

Question from Code

v1

When given any input, why does the printf output "(null)"?

char *scan; scanf("%s", scan); printf("%s", scan);

63c648c75f004bf4898cffa4

2023-01-28T09:45:34.682Z

Help Fix Code

v1

char *scan; scanf("%s", scan); printf("%s", scan);

Code should read a string of any length from stdin and immediately print the string.

63c648c75f004bf4898cffa4

2023-01-28T09:56:35.523Z

Help Fix Code

v1

char perm_required[3]; if (argc == 3) { perm_required = "abc"; } else { perm_required = "def"; }

Initialize a string perm_required. Set perm_required to "abc" if argc == 3, and "def" otherwise.

63c648c75f004bf4898cffa4

2023-01-28T10:06:24.693Z

General Question

v1

Is it possible to initialize a boolean and reassign its value for use later in a program?

63c648c75f004bf4898cffa4

2023-01-28T10:15:49.144Z

Help Write Code

v1

Initialize a string, then reassign its value so it does not contain the first character.

63c648c75f004bf4898cffa4

2023-01-28T10:20:20.234Z

General Question

v1

Does c allow you to create slices of strings?

63c648c75f004bf4898cffa4

2023-01-28T10:33:32.010Z

General Question

v1

Why do I get "error: unknown type name ‘bool’" when I attempt to declare a boolean?

63c648c75f004bf4898cffa4

2023-01-28T10:40:29.137Z

General Question

v1

How could I print out boolean values using printf?

63c648c75f004bf4898cffa4

2023-02-10T19:24:10.744Z

General Question

v1

Provide an example of code that allocates space on the heap for a two-dimensional array.

63c648c75f004bf4898cffa4

2023-02-10T19:36:35.921Z

Help Write Code

v1

Allocate space on the heap for an array of structs. Set each element of the array to an initialized instance of the struct.

63c648c75f004bf4898cffa4

2023-02-10T19:50:40.459Z

General Question

v1

How can I free the space that was previously allocated on the heap for a two-dimensional array?

63c648c75f004bf4898cffa4

2023-02-15T00:07:19.507Z

Help Write Code

v1

Initialize an empty char array of length n. Create any string s. Return 0 if the char array has enough space to store a copy of s using strcpy including the null terminator, and 1 if it does not have enough space.

63c648c75f004bf4898cffa4

2023-02-15T00:09:13.312Z

General Question

v1

How can I find the length of a char array if its length is unknown?

63c648c75f004bf4898cffa4

2023-02-15T00:24:49.053Z

Help Write Code

v1

Check that a string stored in a char array is equal to another string.

63c648c75f004bf4898cffa4

2023-02-15T08:03:40.725Z

Help Write Code

v1

Create a function that appends a new struct to the end of a linked list. Its argument is of type (struct **list), and (*list) points to the head of the list.

63c648c75f004bf4898cffa4

2023-02-15T08:24:08.233Z

Help Fix Code

v1

int create_user(const char *name, User **user_ptr_add) { // Initialize user User newuser; strcpy(newuser.name, name); newuser.next = NULL; User *curr = *user_ptr_add; // Traverse list of users while (curr->next != NULL) { // Check if name already exists if (strcmp(curr->name, name) == 0) { return 1; } curr = curr->next; } // Add newuser to end of list curr->next = &newuser; return 0; }

If any node of the linked list user_ptr_add has attribute name equal to argument name, function should return 1. However, the function does not check the last node of the list.

63c648c75f004bf4898cffa4

2023-02-15T08:26:54.973Z

Question from Code

v1

How do I ensure that the while loop also checks the last node of linked list user_ptr_add?

int create_user(const char *name, User **user_ptr_add) { // Initialize user User newuser; strcpy(newuser.name, name); newuser.next = NULL; User *curr = *user_ptr_add; // Traverse list of users while (curr->next != NULL) { // Check if name already exists if (strcmp(curr->name, name) == 0) { return 1; } curr = curr->next; } // Add newuser to end of list curr->next = &newuser; return 0; }

63c648c75f004bf4898cffa4

2023-02-15T09:13:46.894Z

General Question

v1

How can you determine how many elements are currently stored in an array?

63c648c75f004bf4898cffa4

2023-02-15T09:55:28.082Z

Help Write Code

v1

Initialize an array for 10 structs. Add between 1 to 10 structs to the array. Determine how many structs are in the array (do not count indices that don't contain a struct).

63c648c75f004bf4898cffa4

2023-02-15T09:56:48.373Z

General Question

v1

How do I count how many elements are in an array of integers, not counting indices that don't hold any value?

63c648c75f004bf4898cffa4

2023-02-16T00:12:18.913Z

General Question

v1

How can I check if an element of an array has not been assigned yet?

63c648c75f004bf4898cffa4

2023-02-16T00:24:04.079Z

Help Fix Code

v1

int delete_user(const char *name, User **user_ptr_del) { User *curr = *user_ptr_del; User *prev = curr; int found = 0; char *friend_names[MAX_FRIENDS]; // Traverse list of users while (curr != NULL) { // Check if current user has given name if (strcmp(curr->name, name) == 0) { found = 1; User *curr_friend; // Iterate over friend list for (int i = 0; i < MAX_FRIENDS; i++) { curr_friend = (curr->friends)[i]; // Check if current user is empty if (curr_friend->name == NULL) { break; } else { // If not, append name to list of friend names friend_names[i] = curr_friend->name; } } // Remove user from user list if (strcmp(prev->name, curr->name) == 0) { // If current user is only user *user_ptr_del = NULL; } else { prev->next = curr->next; } break; } prev = curr; curr = curr->next; } // Check if user was not found if (!(found)) { return 1; } // Remove user from all friends' lists char *curr_friend; for (int i = 0; i < MAX_FRIENDS; i++) { curr_friend = friend_names[i]; printf("%s\n", curr_friend); // Check if current user is empty if (curr_friend == NULL) { break; } // Remove user from this friend's list delete_friend(name, curr_friend, user_ptr_del); } // Free space allocated for user free(curr); return 0; }

The friend_names array should contain the names of friends contained in curr. However, the array also contains garbage values, making it impossible to check for NULL strings.

63c648c75f004bf4898cffa4

2023-02-16T00:24:40.111Z

General Question

v1

How do I initialize an array of char * to all NULL values?

63c648c75f004bf4898cffa4

2023-02-16T00:37:40.607Z

General Question

v1

How can I free the space allocated for a struct?

63c648c75f004bf4898cffa4

2023-02-16T01:20:45.282Z

General Question

v1

How do I free space allocated for an array of structs?

63c648c75f004bf4898cffa4

2023-02-16T01:22:36.494Z

Help Fix Code

v1

int delete_user(const char *name, User **user_ptr_del) { User *curr = *user_ptr_del; User *prev = curr; int found = 0; char *friend_names[MAX_FRIENDS] = {NULL}; // Traverse list of users while (curr != NULL) { // Check if current user has given name if (strcmp(curr->name, name) == 0) { found = 1; User *curr_friend; // Iterate over friend list for (int i = 0; i < MAX_FRIENDS; i++) { curr_friend = (curr->friends)[i]; // Check if current user is empty if (curr_friend->name == NULL) { break; } else { // If not, append name to list of friend names friend_names[i] = curr_friend->name; } } // Remove user from user list if (strcmp(prev->name, curr->name) == 0) { // If current user is only user *user_ptr_del = NULL; } else { prev->next = curr->next; } break; } prev = curr; curr = curr->next; } // Check if user was not found if (!(found)) { return 1; } // Remove user from all friends' lists char *curr_friend; for (int i = 0; i < MAX_FRIENDS; i++) { curr_friend = friend_names[i]; // Check if current user is empty if (curr_friend == NULL) { break; } // Remove user from this friend's list delete_friend(name, curr_friend, user_ptr_del); } // Free space allocated for user's posts Post *curr_post = curr->first_post; Post *next_post; while (curr_post != NULL) { next_post = curr_post->next; free(curr_post->author); free(curr_post->contents); free(curr_post->date); free(curr_post); curr_post = next_post; } // Free space allocated for user's friends User *friend; for (int i = 0; i < MAX_FRIENDS; i++) { friend = (curr->friends)[i]; free(friend); } // Free space allocated for user printf("%s\n", curr->name); free(curr->name); if (strcmp(curr->profile_pic, "\0") != 0) { free(curr->profile_pic); } free(curr->friends); free(curr); return 0; }

Function should free array of structs on line 83. Program returns invalid pointer error.

63c648c75f004bf4898cffa4

2023-03-03T10:29:42.480Z

Question from Code

v1

Why does "Bananas" get printed twice?

#include <stdio.h> #include <stdlib.h> #include <unistd.h> int main(void) { printf("Mangoes\n"); int r = fork(); printf("Apples\n"); if (r == 0) { sleep(1); printf("Oranges\n"); int k = fork(); if (k >= 0) { printf("Bananas\n"); } } else if (r > 0) { printf("Peaches\n"); for (int i = 0; i < 3; i++) { if ((r = fork()) == 0) { sleep(1); printf("Pears\n"); exit(0); printf("Nectarines\n"); } else if (r > 0) { printf("Plums\n"); } } } return 0; }

63c648c75f004bf4898cffa4

2023-03-03T23:11:58.718Z

Question from Code

v1

Why does bananas get printed twice?

int main(void) { printf("Mangoes\n"); int r = fork(); printf("Apples\n"); if (r == 0) { sleep(1); printf("Oranges\n"); int k = fork(); if (k >= 0) { printf("Bananas\n"); } } }

63c648c75f004bf4898cffa4

2023-03-10T12:21:21.033Z

Question from Code

v1

Why doesn't the validate program receive all the input from the pipe?

if (r > 0) { // Parent process // Close read end of pipe if ((close(fd[0])) == -1) { perror("close"); } // Write user_id and password to pipe int w_user = write(fd[1], user_id, MAXLINE); int w_pass = write(fd[1], password, MAXLINE); if (w_user == -1 || w_pass == -1) { perror("write"); } // Close write end of pipe if ((close(fd[1])) == -1) { perror("close"); } // Get status of child process int status; wait(&status); if (WIFEXITED(status)) { int exit_status = WEXITSTATUS(status); printf("Status: %d\n", exit_status); // Print message corresponding to status if (exit_status == 0) { printf("%s\n", SUCCESS); } else if (exit_status == 1) { perror("Child error"); } else if (exit_status == 2) { printf("%s\n", INVALID); } else { printf("%s\n", NO_USER); } } else { perror("exit"); } } else if (r == 0) { // Child process // Close write end of pipe if ((close(fd[1])) == -1) { perror("close"); } // Read stdin from pipe if ((dup2(fd[0], fileno(stdin))) == -1) { perror("dup2"); } // Run validate execl("./validate", "validate", NULL); perror("execl"); }

63c648c75f004bf4898cffa4

2023-03-10T12:26:13.993Z

Help Fix Code

v1

if (r > 0) { // Parent process // Close read end of pipe if ((close(fd[0])) == -1) { perror("close"); } // Write user_id and password to pipe int w_user = write(fd[1], user_id, MAXLINE); int w_pass = write(fd[1], password, MAXLINE); if (w_user == -1 || w_pass == -1) { perror("write"); } // Close write end of pipe if ((close(fd[1])) == -1) { perror("close"); } // Get status of child process int status; wait(&status); if (WIFEXITED(status)) { int exit_status = WEXITSTATUS(status); printf("Status: %d\n", exit_status); // Print message corresponding to status if (exit_status == 0) { printf("%s\n", SUCCESS); } else if (exit_status == 1) { perror("Child error"); } else if (exit_status == 2) { printf("%s\n", INVALID); } else { printf("%s\n", NO_USER); } } else { perror("exit"); } } else if (r == 0) { // Child process // Close write end of pipe if ((close(fd[1])) == -1) { perror("close"); } // Read stdin from pipe if ((dup2(fd[0], fileno(stdin))) == -1) { perror("dup2"); } // Run validate execl("./validate", "validate", NULL); perror("execl"); }

Ensure that the validate program can receive both user_id and password from the parent process.

63c648c75f004bf4898cffa4

2023-03-10T13:06:15.813Z

General Question

v2

When should I use exit as opposed to return?

63c648c75f004bf4898cffa4

2023-03-15T10:31:32.427Z

General Question

v2

How do I read lines from an open file?

63c648c75f004bf4898cffa4

2023-03-15T10:50:28.012Z

General Question

v2

How would I use strtok?

63c648c75f004bf4898cffa4

2023-03-15T11:25:34.374Z

General Question

v2

Is there an equivalent of the python continue statement in c?

63c648c75f004bf4898cffa4

2023-03-15T13:14:21.349Z

General Question

v2

How can I check whether a string is contained in another string?

63c648c75f004bf4898cffa4

2023-03-15T22:29:28.402Z

Help Write Code

v2

Create an array of strings where user input adds the new string to the array. It is unknown how many strings the user will enter.

63c648c75f004bf4898cffa4

2023-03-15T23:11:24.278Z

General Question

v2

How can I access the contents of a file multiple times without reopening it?

63c648c75f004bf4898cffa4

2023-03-15T23:50:58.773Z

General Question

v2

Why does strtok return garbage values?

63c648c75f004bf4898cffa4

2023-03-17T07:37:52.311Z

General Question

v2

Provide an example of how to use setitimer.

63c648c75f004bf4898cffa4

2023-03-24T22:23:17.740Z

General Question

v2

How is strchr used?

63c648c75f004bf4898cffa4

2023-03-31T18:28:41.088Z

Explain Code

v2

int main(void) { // Create the socket FD. int sock_fd = socket(AF_INET, SOCK_STREAM, 0); if (sock_fd < 0) { perror("client: socket"); exit(1); } // Set the IP and port of the server to connect to. struct sockaddr_in server; server.sin_family = AF_INET; server.sin_port = htons(PORT); if (inet_pton(AF_INET, "127.0.0.1", &server.sin_addr) < 1) { perror("client: inet_pton"); close(sock_fd); exit(1); } // Connect to the server. if (connect(sock_fd, (struct sockaddr *)&server, sizeof(server)) == -1) { perror("client: connect"); close(sock_fd); exit(1); } // Get the user to provide a name. char buf[2 * BUF_SIZE + 2]; // 2x to allow for usernames printf("Please enter a username: "); fflush(stdout); int num_read = read(STDIN_FILENO, buf, BUF_SIZE); if (num_read == 0) { close(sock_fd); exit(0); } buf[num_read] = '\0'; if (write(sock_fd, buf, num_read) != num_read) { perror("client: write"); close(sock_fd); exit(1); } // Read input from the user and send it to the server. Echo any output // received from the server. while (1) { num_read = read(STDIN_FILENO, buf, BUF_SIZE); if (num_read == 0) { break; } buf[num_read] = '\0'; if (write(sock_fd, buf, num_read) != num_read) { perror("client: write"); close(sock_fd); exit(1); } num_read = read(sock_fd, buf, sizeof(buf) - 1); if (num_read == 0) { break; } buf[num_read] = '\0'; printf("[Server] %s", buf); } close(sock_fd); return 0; }

63c648c75f004bf4898cffa4

2023-03-31T18:35:30.853Z

Explain Code

v2

int main(void) { struct sockname users[MAX_CONNECTIONS]; for (int index = 0; index < MAX_CONNECTIONS; index++) { users[index].sock_fd = -1; users[index].username = NULL; } int sock_fd = socket(AF_INET, SOCK_STREAM, 0); if (sock_fd < 0) { perror("server: socket"); exit(1); } struct sockaddr_in server; server.sin_family = AF_INET; server.sin_port = htons(PORT); server.sin_addr.s_addr = INADDR_ANY; int on = 1; int status = setsockopt(sock_fd, SOL_SOCKET, SO_REUSEADDR, (const char *)&on, sizeof(on)); if (status == -1) { perror("setsockopt -- REUSEADDR"); } memset(&server.sin_zero, 0, 8); if (bind(sock_fd, (struct sockaddr *)&server, sizeof(server)) < 0) { perror("server: bind"); close(sock_fd); exit(1); } if (listen(sock_fd, MAX_BACKLOG) < 0) { perror("server: listen"); close(sock_fd); exit(1); } int max_fd = sock_fd; fd_set all_fds; FD_ZERO(&all_fds); FD_SET(sock_fd, &all_fds); while (1) { fd_set listen_fds = all_fds; if (select(max_fd + 1, &listen_fds, NULL, NULL, NULL) == -1) { perror("server: select"); exit(1); } if (FD_ISSET(sock_fd, &listen_fds)) { int client_fd = accept_connection(sock_fd, users); if (client_fd > max_fd) { max_fd = client_fd; } FD_SET(client_fd, &all_fds); printf("Accepted connection\n"); } for (int index = 0; index < MAX_CONNECTIONS; index++) { if (users[index].sock_fd > -1 && FD_ISSET(users[index].sock_fd, &listen_fds)) { int client_closed = read_from(index, users); if (client_closed > 0) { FD_CLR(client_closed, &all_fds); printf("Client %d disconnected\n", client_closed); } else { printf("Echoing message from client %d\n", users[index].sock_fd); } } } } return 1; }

63c648c75f004bf4898cffa4

2023-03-31T19:45:16.074Z

General Question

v2

Given username and message strings, how would I construct a new string "<username>: <message>"?

63c648c75f004bf4898cffa4

2023-03-31T21:15:17.722Z

Help Fix Code

v2

User should be able to type a sequence of messages, and server program will echo messages back to user. However, the program begins an infinite loop of printing that message. How do I prevent this?

int max_fd = sock_fd; if (STDIN_FILENO > sock_fd) { max_fd = STDIN_FILENO; } fd_set all_fds; FD_ZERO(&all_fds); FD_SET(sock_fd, &all_fds); FD_SET(STDIN_FILENO, &all_fds); // Read input from the user and send it to the server. Echo any output // received from the server. while (1) { fd_set listen_fds = all_fds; if (select(max_fd + 1, &listen_fds, NULL, NULL, NULL) == -1) { perror("client: select"); exit(1); } /* * We should really send "\r\n" too, so the server can identify partial * reads, but you are not required to handle partial reads in this lab. */ if (write(sock_fd, buf, num_read) != num_read) { perror("client: write"); close(sock_fd); exit(1); } // Check from stdin if (FD_ISSET(STDIN_FILENO, &listen_fds)) { num_read = read(STDIN_FILENO, buf, BUF_SIZE); if (num_read == 0) { break; } buf[num_read] = '\0'; // Send user message to server if (write(sock_fd, buf, num_read) != num_read) { perror("client: write"); close(sock_fd); exit(1); } } // Check from socket if (FD_ISSET(sock_fd, &listen_fds)) { num_read = read(sock_fd, buf, sizeof(buf) - 1); if (num_read == 0) { break; } buf[num_read] = '\0'; // Print server message to stdout printf("[Server] %s", buf); } }

63c648c75f004bf4898cffa4

2023-04-04T15:29:59.258Z

General Question

v2

How could you use snprintf to repeatedly write additional text to the end of the same string?

63c648c75f004bf4898cffa4

2023-04-04T15:31:54.667Z

General Question

v2

How would one use perror when malloc fails?

63c648c75f004bf4898cffa4

2023-04-23T05:55:32.895Z

General Question

v2

In shell programming, what is the purpose of /dev/null?

63c648c75f004bf4898cffa4

2023-04-23T06:25:25.324Z

Question from Code

v2

This is a shell program. What is the for loop doing?

#!/ usr / bin / sh path=/u/csc209h/winter/pub/shell-prog upper_bound=7 for i in `seq 1 "$upper_bound"` do prev=`expr $i - 1` next=`expr $i + 1` if (! diff "${path}/${i}" "${path}/${prev}" > /dev/null) && (! diff "${path}/${i}" "${path}/${prev}" > /dev/null) then echo "${path}/${i}" is the odd one out #Can exit here exit 0 fi done

63c648c75f004bf4898cffa4

2023-04-25T21:13:12.460Z

General Question

v2

What causes a compilation error and runtime/logical errors?

63c648c85f004bf4898cffae

2023-03-10T22:06:13.106Z

Explain Code

v2

#include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/types.h> #include <sys/wait.h> #include <unistd.h> #define MAXLINE 256 #define SUCCESS "Password verified\n" #define INVALID "Invalid password\n" #define NO_USER "No such user\n" int main(void) { char user_id[MAXLINE]; char password[MAXLINE]; int status; int ret; int pipe_fd[2]; if (fgets(user_id, MAXLINE, stdin) == NULL) { perror("fgets"); exit(1); } if (fgets(password, MAXLINE, stdin) == NULL) { perror("fgets"); exit(1); };

63c648c85f004bf4898cffae

2023-03-10T22:14:20.851Z

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.

63c648c85f004bf4898cffae

2023-03-10T22:35:20.669Z

Help Write Code

v2

The validate program reads the user id and password from stdin, because if they were given as command-line arguments they would be visible to programs such as ps that inspect the state of the system. 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.

63c648c85f004bf4898cffae

2023-03-10T22:42:45.583Z

Help Fix Code

v2

The validate program reads the user id and password from stdin, because if they were given as command-line arguments they would be visible to programs such as ps that inspect the state of the system. 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.

#include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/types.h> #include <sys/wait.h> #define MAXLINE 256 #define SUCCESS "Password verified\n" #define INVALID "Invalid password\n" #define NO_USER "No such user\n" 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 */ int status; int ret; int pipe_fd[2]; if(fgets(user_id, MAXLINE, stdin) == NULL) { perror("fgets"); exit(1); } if(fgets(password, MAXLINE, stdin) == NULL) { perror("fgets"); exit(1); }; if(strlen(user_id) > MAXLINE || strlen(password) > MAXLINE) { perror("username or password is too long\n"); exit(1); } // TODO if ((pipe(pipe_fd)) == -1) { perror("pipe"); exit(1); } int read_end = pipe_fd[0]; int write_end = pipe_fd[1]; ret = fork(); if (ret < 0) { perror("fork"); exit(1); } if (ret == 0) { close(write_end); dup2(read_end, STDIN_FILENO); execl("./validate", "validate", NULL); } else if (ret > 0) { close(read_end); int user_len = strlen(user_id); int passwd_len = strlen(password); write(write_end, &user_len, sizeof(char)); write(write_end, &passwd_len, sizeof(char)); close(write_end); wait(&status); if ((ret = wait(&status)) == -1) { perror("wait"); exit(1); } if (WIFEXITED(status)) { int output = WEXITSTATUS(status); if (output == 0){ printf(SUCCESS); } else if (output == 2){ printf(INVALID); } else if (output == 3) { printf(NO_USER); } } } return 0; }

63c648c85f004bf4898cffae

2023-03-10T22:46:06.830Z

Help Fix Code

v2

The validate program reads the user id and password from stdin, because if they were given as command-line arguments they would be visible to programs such as ps that inspect the state of the system. 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.

#include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/types.h> #include <sys/wait.h> #define MAXLINE 256 #define SUCCESS "Password verified\n" #define INVALID "Invalid password\n" #define NO_USER "No such user\n" 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 */ int status; int ret; int pipe_fd[2]; if(fgets(user_id, MAXLINE, stdin) == NULL) { perror("fgets"); exit(1); } if(fgets(password, MAXLINE, stdin) == NULL) { perror("fgets"); exit(1); }; if(strlen(user_id) > MAXLINE || strlen(password) > MAXLINE) { perror("username or password is too long\n"); exit(1); } // TODO if ((pipe(pipe_fd)) == -1) { perror("pipe"); exit(1); } int read_end = pipe_fd[0]; int write_end = pipe_fd[1]; ret = fork(); if (ret < 0) { perror("fork"); exit(1); } if (ret == 0) { close(write_end); dup2(read_end, STDIN_FILENO); execl("./validate", "validate", NULL); } else if (ret > 0) { close(read_end); write(write_end, &user_id, sizeof(char)); write(write_end, &password, sizeof(char)); close(write_end); wait(&status); if ((ret = wait(&status)) == -1) { perror("wait"); exit(1); } if (WIFEXITED(status)) { int output = WEXITSTATUS(status); if (output == 0){ printf(SUCCESS); } else if (output == 2){ printf(INVALID); } else if (output == 3) { printf(NO_USER); } } } return 0; }

63c648c85f004bf4898cffae

2023-03-10T22:52:50.222Z

Help Fix Code

v2

The validate program reads the user id and password from stdin, because if they were given as command-line arguments they would be visible to programs such as ps that inspect the state of the system. 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.

#include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/types.h> #include <sys/wait.h> #define MAXLINE 256 #define SUCCESS "Password verified\n" #define INVALID "Invalid password\n" #define NO_USER "No such user\n" 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 */ int status; int ret; int pipe_fd[2]; if(fgets(user_id, MAXLINE, stdin) == NULL) { perror("fgets"); exit(1); } if(fgets(password, MAXLINE, stdin) == NULL) { perror("fgets"); exit(1); }; if(strlen(user_id) > MAXLINE || strlen(password) > MAXLINE) { perror("username or password is too long\n"); exit(1); } // TODO if ((pipe(pipe_fd)) == -1) { perror("pipe"); exit(1); } int read_end = pipe_fd[0]; int write_end = pipe_fd[1]; ret = fork(); if (ret < 0) { perror("fork"); exit(1); } if (ret == 0) { close(write_end); dup2(read_end, STDIN_FILENO); execl("./validate", "validate", NULL); close(read_end); exit(0); } else if (ret > 0) { close(read_end); write(write_end, &user_id, sizeof(char)); write(write_end, &password, sizeof(char)); close(write_end); wait(&status); if ((ret = wait(&status)) == -1) { perror("wait"); exit(1); } if (WIFEXITED(status)) { int output = WEXITSTATUS(status); if (output == 0){ printf(SUCCESS); } else if (output == 2){ printf(INVALID); } else if (output == 3) { printf(NO_USER); } } } return 0; }

63c648c85f004bf4898cffae

2023-03-10T22:59:34.312Z

Help Fix Code

v2

The validate program reads the user id and password from stdin, because if they were given as command-line arguments they would be visible to programs such as ps that inspect the state of the system. 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.

#include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/types.h> #include <sys/wait.h> #define MAXLINE 256 #define SUCCESS "Password verified\n" #define INVALID "Invalid password\n" #define NO_USER "No such user\n" 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 */ int status; int ret; int pipe_fd[2]; if(fgets(user_id, MAXLINE, stdin) == NULL) { perror("fgets"); exit(1); } if(fgets(password, MAXLINE, stdin) == NULL) { perror("fgets"); exit(1); }; if(strlen(user_id) > MAXLINE || strlen(password) > MAXLINE) { perror("username or password is too long\n"); exit(1); } // TODO if ((pipe(pipe_fd)) == -1) { perror("pipe"); exit(1); } int read_end = pipe_fd[0]; int write_end = pipe_fd[1]; ret = fork(); if (ret < 0) { perror("fork"); exit(1); } if (ret == 0) { close(write_end); dup2(read_end, STDIN_FILENO); execl("./validate", "validate", NULL); close(read_end); exit(0); } else if (ret > 0) { int len_user = strlen(user_id); int len_pswd = strlen(password); close(read_end); write(write_end, &user_id, len_user + 1); write(write_end, &password, len_pswd + 1); close(write_end); wait(&status); if ((ret = wait(&status)) == -1) { perror("wait"); exit(1); } if (WIFEXITED(status)) { int output = WEXITSTATUS(status); if (output == 0){ printf(SUCCESS); } else if (output == 2){ printf(INVALID); } else if (output == 3) { printf(NO_USER); } } } return 0; }

63c648c85f004bf4898cffae

2023-03-10T23:03:19.176Z

Help Fix Code

v2

The validate program reads the user id and password from stdin, because if they were given as command-line arguments they would be visible to programs such as ps that inspect the state of the system. 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.

#include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/types.h> #include <sys/wait.h> #define MAXLINE 256 #define SUCCESS "Password verified\n" #define INVALID "Invalid password\n" #define NO_USER "No such user\n" 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 */ int status; int ret; int pipe_fd[2]; if(fgets(user_id, MAXLINE, stdin) == NULL) { perror("fgets"); exit(1); } if(fgets(password, MAXLINE, stdin) == NULL) { perror("fgets"); exit(1); }; if(strlen(user_id) > MAXLINE || strlen(password) > MAXLINE) { perror("username or password is too long\n"); exit(1); } // TODO if ((pipe(pipe_fd)) == -1) { perror("pipe"); exit(1); } int read_end = pipe_fd[0]; int write_end = pipe_fd[1]; ret = fork(); if (ret < 0) { perror("fork"); exit(1); } if (ret == 0) { close(write_end); dup2(read_end, STDIN_FILENO); execl("./validate", "validate", NULL); } else if (ret > 0) { int len_user = strlen(user_id); int len_pswd = strlen(password); close(read_end); write(write_end, user_id, len_user + 1); write(write_end, password, len_pswd + 1); close(write_end); wait(&status); if ((ret = wait(&status)) == -1) { perror("wait"); exit(1); } if (WIFEXITED(status)) { int output = WEXITSTATUS(status); if (output == 0){ printf(SUCCESS); } else if (output == 2){ printf(INVALID); } else if (output == 3) { printf(NO_USER); } } } return 0; }

63c648c85f004bf4898cffae

2023-03-10T23:08:29.009Z

Help Fix Code

v2

The validate program reads the user id and password from stdin, because if they were given as command-line arguments they would be visible to programs such as ps that inspect the state of the system. 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.

#include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/types.h> #include <sys/wait.h> #define MAXLINE 256 #define SUCCESS "Password verified\n" #define INVALID "Invalid password\n" #define NO_USER "No such user\n" 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 */ int status; int ret; int pipe_fd[2]; if(fgets(user_id, MAXLINE, stdin) == NULL) { perror("fgets"); exit(1); } if(fgets(password, MAXLINE, stdin) == NULL) { perror("fgets"); exit(1); }; if(strlen(user_id) > MAXLINE || strlen(password) > MAXLINE) { perror("username or password is too long\n"); exit(1); } // TODO if ((pipe(pipe_fd)) == -1) { perror("pipe"); exit(1); } int read_end = pipe_fd[0]; int write_end = pipe_fd[1]; ret = fork(); if (ret < 0) { perror("fork"); exit(1); } if (ret == 0) { close(write_end); dup2(read_end, STDIN_FILENO); execl("./validate", "validate", NULL); } else if (ret > 0) { int len_user = strlen(user_id); int len_pswd = strlen(password); close(read_end); write(write_end, user_id, len_user + 2); write(write_end, password, len_pswd + 2); close(write_end); wait(&status); if ((ret = wait(&status)) == -1) { perror("wait"); exit(1); } if (WIFEXITED(status)) { int output = WEXITSTATUS(status); if (output == 0){ printf(SUCCESS); } else if (output == 2){ printf(INVALID); } else if (output == 3) { printf(NO_USER); } } } }

63c648c85f004bf4898cffae

2023-03-10T23:10:58.541Z

Help Fix Code

v2

The validate program reads the user id and password from stdin, because if they were given as command-line arguments they would be visible to programs such as ps that inspect the state of the system. 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.

#include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/types.h> #include <sys/wait.h> #define MAXLINE 256 #define SUCCESS "Password verified\n" #define INVALID "Invalid password\n" #define NO_USER "No such user\n" 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 */ int status; int ret; int pipe_fd[2]; if(fgets(user_id, MAXLINE, stdin) == NULL) { perror("fgets"); exit(1); } if(fgets(password, MAXLINE, stdin) == NULL) { perror("fgets"); exit(1); }; if(strlen(user_id) > MAXLINE || strlen(password) > MAXLINE) { perror("username or password is too long\n"); exit(1); } // TODO if ((pipe(pipe_fd)) == -1) { perror("pipe"); exit(1); } int read_end = pipe_fd[0]; int write_end = pipe_fd[1]; ret = fork(); if (ret < 0) { perror("fork"); exit(1); } else if (ret == 0) { close(write_end); dup2(read_end, STDIN_FILENO); execl("./validate", "validate", NULL); } int len_user = strlen(user_id); int len_pswd = strlen(password); close(read_end); write(write_end, user_id, len_user); write(write_end, password, len_pswd); close(write_end); wait(&status); if ((ret = wait(&status)) == -1) { perror("wait"); exit(1); } if (WIFEXITED(status)) { int output = WEXITSTATUS(status); if (output == 0){ printf(SUCCESS); } else if (output == 2){ printf(INVALID); } else if (output == 3) { printf(NO_USER); } } }

63c648c85f004bf4898cffae

2023-03-11T20:50:51.927Z

Help Write Code

v2

our 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.

63c648c85f004bf4898cffae

2023-03-13T14:05:02.352Z

Explain Code

v2

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

63c648c85f004bf4898cffae

2023-03-13T14:08:34.454Z

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 "); struct sigaction act; act.sa_handler = handler; act.sa_flags = 0; sigemptyset(&act.sa_mask); sigaction(SIGINT, &act, NULL); x += 2; fprintf(stderr, "outside %d", x); return 0; }

63c648c85f004bf4898cffae

2023-03-13T14:09:31.552Z

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 C?

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

63c648c85f004bf4898cffae

2023-03-13T14:15:22.144Z

Question from Code

v2

What does the program print to stderr if the user presses Ctrl+C before x += 2?

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

63c648c85f004bf4898cffae

2023-03-13T14:16:17.110Z

Question from Code

v2

What does the program print to stderr if the user presses Ctrl+C after x += 2?

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

63c648c85f004bf4898cffae

2023-03-13T14:18:37.248Z

Question from Code

v2

What does the program print to stderr if the user presses Ctrl+C right after calling x += 2?

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