user_id
stringlengths 24
24
| time
stringlengths 24
24
| feature_type
stringclasses 5
values | feature_version
stringclasses 2
values | input_question
stringlengths 1
1.24k
⌀ | input_code
stringlengths 2
18.5k
⌀ | input_intention
stringlengths 1
2.48k
⌀ | input_task_description
stringlengths 18
3.32k
⌀ |
|---|---|---|---|---|---|---|---|
63c647dc5f004bf4898cf752 | 2023-04-04T22:31:07.925Z | Help Fix Code | v2 | How to change the code such that it prints out whether it is an old socket or new socket accordingly? | 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);
write(client_socket, "What is your user name?\n", 24);
}
| null | null |
63c647dc5f004bf4898cf752 | 2023-04-05T00:49:30.347Z | General Question | v2 | What is the difference between accept and accept connection in c? | null | null | null |
63c647dc5f004bf4898cf752 | 2023-04-05T01:04:56.715Z | General Question | v2 | How to fix this error? 'User’ declared inside parameter list will not be visible outside of this definition or declaration [-Werror]
212 | void cleanup_args_for_processing(struct User *user_list, int client_fd) | null | null | null |
63c647dc5f004bf4898cf752 | 2023-04-05T01:09:15.238Z | General Question | v2 | What is the problem with this?
expected expression before ‘User’
408 | check_and_add_user(User * user_list, int client_fd);
| ^~~~
error: too few arguments to function ‘check_and_add_user’
408 | check_and_add_user(User * user_list, int client_fd);
| ^~~~~~~~~~~~~~~~~~
note: declared here
256 | void check_and_add_user(User *user_list, int client_fd) | null | null | null |
63c647dc5f004bf4898cf752 | 2023-04-05T01:25:40.218Z | General Question | v2 | Why is it asking for more arguments?
function call: check_and_add_user(User *user_list, int client_fd);
function header: 256 void check_and_add_user(User *user_list, int client_fd)
| null | null | null |
63c647dc5f004bf4898cf752 | 2023-04-05T02:10:13.699Z | Help Fix Code | v2 | How to change this code such that instead of using sockname with is an array, it uses a linked list structure and loops through the list? | int accept_connection(int fd, struct sockname *users)
{
int user_index = 0;
while (users[user_index].sock_fd != -1)
{
user_index++;
}
int client_fd = accept(fd, NULL, NULL);
if (client_fd < 0)
{
perror("server: accept");
close(fd);
exit(1);
}
users[user_index].sock_fd = client_fd;
users[user_index].username = NULL;
return client_fd;
} | null | null |
63c647dc5f004bf4898cf752 | 2023-04-05T14:30:15.569Z | General Question | v2 | How to fix this error invalid type argument of ‘->’ (have ‘fd_set’ {aka ‘struct <anonymous>’})
471 | if (curr_client->fd > -1 && FD_ISSET(curr_client->fd, listen_fds))
| null | null | null |
63c647dc5f004bf4898cf752 | 2023-04-05T14:46:58.120Z | Help Fix Code | v2 | Read the first line from the user input, that is the username. Check if the username is already in user_list, if not, add it as the last node in user_list. | void check_and_add_user(User *user_list, int client_fd)
{
char buf[INPUT_BUFFER_SIZE] = {'\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
char name[MAX_NAME];
User *curr = user_list;
int nbytes;
while ((nbytes = read(client_fd, after, room)) > 0)
{
inbuf += nbytes;
int where;
while ((where = find_network_newline(buf, inbuf)) > 0)
{
buf[where - 2] = '\0';
strcpy(name, buf);
printf("test (name): %s\n", name);
if (curr != NULL)
{
while (curr->next != NULL)
{
if (strcmp(name, curr->name) == 0)
{ // there is already a user with this name
write(client_fd, "Welcome Back\n", 13);
break;
}
curr = curr->next;
}
if (curr->next == NULL)
{ // create a new user
struct user *new_user = calloc(sizeof(User), 1);
strncpy(new_user->name, buf, MAX_NAME); // didn't malloc space for name, thus, it is read-only
strcat(new_user->name, "\r\n");
new_user->next = NULL;
curr->next = new_user;
}
}
else
{ // curr is NULL and the linkedlist is empty
struct user *new_user = calloc(sizeof(User), 1);
strncpy(new_user->name, buf, MAX_NAME);
strcat(new_user->name, "\r\n");
new_user->next = NULL;
curr = new_user;
}
inbuf = inbuf - where;
for (int i = 0; i < where; i++)
{
buf[i] = '\0';
}
memmove(buf, buf + where, inbuf);
for (int i = where; i < INPUT_BUFFER_SIZE; i++)
{
buf[i] = '\0';
}
}
after = buf + inbuf;
room = INPUT_BUFFER_SIZE - inbuf;
}
} | null | null |
63c647dc5f004bf4898cf752 | 2023-04-05T16:00:41.850Z | Help Fix Code | v2 | how to fix friend_server.c:369:12: error: function returns address of local variable [-Werror=return-local-addr]
369 | return name;
| char * check_and_add_user(User *user_list, int client_fd)
{
char buf[INPUT_BUFFER_SIZE] = {'\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
char name[MAX_NAME];
User *curr = user_list;
int nbytes;
while ((nbytes = read(client_fd, after, room)) > 0)
{
inbuf += nbytes;
int where;
while ((where = find_network_newline(buf, inbuf)) > 0)
{
buf[where - 2] = '\0';
strcpy(name, buf);
printf("test (name): %s\n", name);
if (curr != NULL)
{
while (curr->next != NULL)
{
if (strcmp(name, curr->name) == 0)
{ // there is already a user with this name
write(client_fd, "Welcome Back\n", 13);
break;
}
curr = curr->next;
}
if (curr->next == NULL)
{ // create a new user
struct user *new_user = calloc(sizeof(User), 1);
strncpy(new_user->name, buf, MAX_NAME); // didn't malloc space for name, thus, it is read-only
strcat(new_user->name, "\r\n");
new_user->next = NULL;
curr->next = new_user;
printf("added_user succesfully, not first\n");
}
}
else
{ // curr is NULL and the linkedlist is empty
struct user *new_user = calloc(sizeof(User), 1);
strncpy(new_user->name, buf, MAX_NAME);
strcat(new_user->name, "\r\n");
new_user->next = NULL;
curr = new_user;
printf("added_user succesfully, first\n");
}
inbuf = inbuf - where;
for (int i = 0; i < where; i++)
{
buf[i] = '\0';
}
memmove(buf, buf + where, inbuf);
for (int i = where; i < INPUT_BUFFER_SIZE; i++)
{
buf[i] = '\0';
}
}
after = buf + inbuf;
room = INPUT_BUFFER_SIZE - inbuf;
printf("check and add user complete \n");
}
return name;
} | null | null |
63c647dc5f004bf4898cf752 | 2023-04-05T16:43:47.015Z | Explain Code | v2 | null | if (FD_ISSET(listen_soc, &listen_fds)) {
client_fd = accept_connection(listen_soc, client_list);
printf("main (test) client fd: %d\n", client_fd);
if (client_fd == -1) {
perror("accept");
return -1;
}
printf("clinet_fd: %d\n", client_fd);
printf("max_fd: %d\n", max_fd);
Client *client_ptr = find_client(client_fd, client_list);
if (client_ptr != NULL) {
printf("client found\n");
}
if (client_ptr == NULL) {
printf("main _ new connection\n");
write(client_fd, "What is your user name?\n", 24);
User *user = check_and_add_user(user_list, client_fd);
Client *temp_client = client_list;
while (temp_client != NULL) {
temp_client = temp_client->next;
}
temp_client->fd = client_fd;
temp_client->user = user;
temp_client->username = user->name;
temp_client->next = NULL;
} else {
cleanup_args_for_processing(user_list, client_fd, client_list);
} | null | null |
63c647dc5f004bf4898cf752 | 2023-04-05T16:44:23.921Z | Help Fix Code | v2 | This code checks if a new connection has been made on the listening socket. If a new connection has been made, it accepts the connection and adds the new client to the client list. If the client is already in the list, it cleans up the arguments for processing. If the client is not in the list, it prompts the client for their username and adds the user to the user list. It then creates a new client object and adds it to the client list. | if (FD_ISSET(listen_soc, &listen_fds))
{
client_fd = accept_connection(listen_soc, client_list);
printf("main (test) client fd: %d\n", client_fd);
if (client_fd == -1)
{
perror("accept");
return -1;
}
printf("clinet_fd: %d\n", client_fd);
printf("max_fd: %d\n", max_fd);
Client *client_ptr = find_client(client_fd, client_list);
if (client_ptr != NULL){
printf("client found\n");
}
if (client_ptr == NULL){ // this is a new socket
printf("main _ new connection\n");
write(client_fd, "What is your user name?\n", 24);
User *user = check_and_add_user(user_list, client_fd);
// strncpy(client_ptr->username, name, MAX_NAME);
// add client_fd into client_list
Client *temp_client = client_list;
while (temp_client != NULL){
temp_client = temp_client->next;
}
temp_client->fd = client_fd;
temp_client->user = user;
temp_client->username = user->name;
temp_client->next = NULL;
} else { // this is not a new socket
cleanup_args_for_processing(user_list, client_fd, client_list);
}
| null | null |
63c647dc5f004bf4898cf752 | 2023-04-05T16:45:54.978Z | Help Fix Code | v2 | How to check if client is already in the list? | if (FD_ISSET(listen_soc, &listen_fds))
{
client_fd = accept_connection(listen_soc, client_list);
printf("main (test) client fd: %d\n", client_fd);
if (client_fd == -1)
{
perror("accept");
return -1;
}
printf("clinet_fd: %d\n", client_fd);
printf("max_fd: %d\n", max_fd);
Client *client_ptr = find_client(client_fd, client_list);
if (client_ptr != NULL){
printf("client found\n");
}
if (client_ptr == NULL){ // this is a new socket
printf("main _ new connection\n");
write(client_fd, "What is your user name?\n", 24);
User *user = check_and_add_user(user_list, client_fd);
// strncpy(client_ptr->username, name, MAX_NAME);
// add client_fd into client_list
Client *temp_client = client_list;
while (temp_client != NULL){
temp_client = temp_client->next;
}
temp_client->fd = client_fd;
temp_client->user = user;
temp_client->username = user->name;
temp_client->next = NULL;
} else { // this is not a new socket
cleanup_args_for_processing(user_list, client_fd, client_list);
}
| null | null |
63c647dc5f004bf4898cf752 | 2023-04-05T17:08:37.613Z | Question from Code | v2 | Why is my code running check_and_add_user even when the client already exist? | if (FD_ISSET(listen_soc, &listen_fds)) {
client_fd = accept_connection(listen_soc, client_list);
printf("main (test) client fd: %d\n", client_fd);
if (client_fd == -1) {
perror("accept");
return -1;
}
printf("clinet_fd: %d\n", client_fd);
printf("max_fd: %d\n", max_fd);
Client *client_ptr = find_client(client_fd, client_list);
if (client_ptr != NULL) {
printf("client found\n");
}
if (client_ptr == NULL) {
printf("main _ new connection\n");
write(client_fd, "What is your user name?\n", 24);
User *user = check_and_add_user(user_list, client_fd);
Client *new_client = (Client *)malloc(sizeof(Client));
new_client->fd = client_fd;
new_client->user = user;
new_client->username = user->name;
new_client->next = NULL;
if (client_list == NULL) {
client_list = new_client;
} else {
Client *temp_client = client_list;
while (temp_client->next != NULL) {
temp_client = temp_client->next;
}
temp_client->next = new_client;
}
} else {
cleanup_args_for_processing(user_list, client_fd, client_list);
} | null | null |
63c647dc5f004bf4898cf752 | 2023-04-05T17:09:32.593Z | Help Fix Code | v2 | return a pointer to the Client structure that corresponds to the given file descriptor, or NULL if no such Client structure exists | Client *find_client(int client_fd, const Client *head)
{
while (head != NULL && head->fd != client_fd)
{
head = head->next;
}
return (Client *)head;
} | null | null |
63c647dc5f004bf4898cf752 | 2023-04-05T17:10:44.972Z | Help Fix Code | v2 | return a pointer to the Client structure that corresponds to the given file descriptor, or NULL if no such Client structure exists | Client *find_client(int client_fd, const Client *client_list)
{
Client *curr = client_list;
while (curr != NULL && curr->fd != client_fd)
{
curr = curr->next;
}
return (Client *)curr;
}
| null | null |
63c647dc5f004bf4898cf752 | 2023-04-05T22:27:40.213Z | Question from Code | v2 | Why does this not write even when there is a user->name that is equal name? | while (curr->next != NULL) {
if (strcmp(curr->name, name) == 0) {
write(client_fd, "Welcome Back\n", 13);
break;
}
curr = curr->next;
} | null | null |
63c647dc5f004bf4898cf752 | 2023-04-05T23:39:21.429Z | General Question | v2 | how to set input stream as client_socket? | null | null | null |
63c647dc5f004bf4898cf752 | 2023-04-06T00:26:43.626Z | Question from Code | v2 | What would be the output if this function is ran on ("list_users", "")? | int tokenize(char *cmd, char **cmd_argv) {
int cmd_argc = 0;
char *next_token = strtok(cmd, DELIM);
while (next_token != NULL) {
if (cmd_argc >= INPUT_ARG_MAX_NUM - 1) {
error("Too many arguments!");
cmd_argc = 0;
break;
}
cmd_argv[cmd_argc] = next_token;
cmd_argc++;
next_token = strtok(NULL, DELIM);
}
return cmd_argc;
} | null | null |
63c647dc5f004bf4898cf752 | 2023-04-06T01:35:41.859Z | Question from Code | v2 | why is strncpy giving me a segmentation fault? | for (int i = 0; i < cmd_argc; i++) {
char new_str[strlen(cmd_argv[i])];
while (cmd_argv[i][j]) {
if (cmd_argv[i][j] != '\r' && cmd_argv[i][j] != '\n' && cmd_argv[i][j] != '\0') {
len++;
new_str[j] = cmd_argv[i][j];
}
strncpy(cmd_argv[i], new_str, len);
}
} | null | null |
63c647dc5f004bf4898cf752 | 2023-04-06T02:37:01.150Z | General Question | v2 | How to solve (.text+0x24): undefined reference to `main'
collect2: error: ld returned 1 exit status | null | null | null |
63c647dc5f004bf4898cf752 | 2023-04-06T18:57:17.335Z | Help Fix Code | v2 | Why is this code not listening for new clients? when there is a new client, it should print hello |
int main(int argc, char *argv[])
{
User *user_list = NULL;
// User *curr = user_list; // curr is the head of the user_list
Client *client_list = NULL;
// Create socket
int listen_soc = socket(AF_INET, SOCK_STREAM, 0);
if (listen_soc == -1)
{
perror("server: socket");
exit(1);
}
// initialize server address
struct sockaddr_in server;
server.sin_family = AF_INET;
server.sin_port = htons(PORT);
memset(&server.sin_zero, 0, 8);
server.sin_addr.s_addr = INADDR_ANY;
/*
* Releasing port as soon as my server process terminates.
*/
int on = 1;
int status = setsockopt(listen_soc, SOL_SOCKET, SO_REUSEADDR, (const char *)&on, sizeof(on));
if (status == -1)
{
perror("setsockopt -- REUSEADDR");
}
memset(&server.sin_zero, 0, 8);
// bind socket to an address
if (bind(listen_soc, (struct sockaddr *)&server, sizeof(struct sockaddr_in)) == -1)
{
perror("server: bind");
close(listen_soc);
exit(1);
}
// Set up a queue in the kernel to hold pending connections.
if (listen(listen_soc, 5) < 0)
{
// listen failed
perror("listen");
exit(1);
}
int max_fd = listen_soc;
fd_set all_fds;
FD_ZERO(&all_fds);
FD_SET(listen_soc, &all_fds);
int client_fd;
while (1)
{
// select updates the fd_set it receives, so we always use a copy and retain the original.
fd_set listen_fds = all_fds;
if (select(max_fd + 1, &listen_fds, NULL, NULL, NULL) == -1)
{
perror("server: select");
exit(1);
}
// Is it the original socket? Create a new connection ...
if (FD_ISSET(listen_soc, &listen_fds))
{
client_fd = accept_connection(listen_soc, client_list);
if (client_fd > max_fd)
{ printf("hello"); }
FD_SET(client_fd, &all_fds);
}
// Check the clients
Client *curr_client = client_list;
while (curr_client != NULL)
{
if (curr_client->fd > -1 && FD_ISSET(curr_client->fd, &listen_fds))
{
int client_closed = cleanup_args_for_processing(user_list, curr_client->fd, client_list); }
curr_client = curr_client->next;
}
}
return 0;
}
| null | null |
63c647dc5f004bf4898cf752 | 2023-04-06T19:40:40.683Z | Help Fix Code | v2 | why is this code never adding to client_list? | if (client_fd > max_fd)
{ // this is a new socket
max_fd = client_fd;
write(client_fd, "What is your user name?\n", 24);
check_and_add_user(user_list, client_fd, client_list);
// add client_fd into client_list
Client *new_client = (Client *)malloc(sizeof(Client));
if (new_client == NULL){
perror("malloc");
exit(1);
}
new_client->fd = client_fd;
// new_client->user = user;
new_client->user = NULL;
new_client->username = NULL;
new_client->next = NULL;
if (client_list == NULL)
{
client_list = new_client;
}
else
{
Client *temp_client = client_list;
while (temp_client->next != NULL)
{
temp_client = temp_client->next;
}
temp_client->next = new_client;
}
} | null | null |
63c647dc5f004bf4898cf752 | 2023-04-06T19:41:50.023Z | Help Fix Code | v2 | why is this code never adding to client_list? | if (client_fd > max_fd)
{ // this is a new socket
write(client_fd, "What is your user name?\n", 24);
check_and_add_user(user_list, client_fd, client_list);
// add client_fd into client_list
Client *new_client = (Client *)malloc(sizeof(Client));
if (new_client == NULL){
perror("malloc");
exit(1);
}
new_client->fd = client_fd;
// new_client->user = user;
new_client->user = NULL;
new_client->username = NULL;
new_client->next = NULL;
if (client_list == NULL)
{
client_list = new_client;
}
else
{
Client *temp_client = client_list;
while (temp_client->next != NULL)
{
temp_client = temp_client->next;
}
temp_client->next = new_client;
}
max_fd = client_fd;
} | null | null |
63c647dc5f004bf4898cf752 | 2023-04-25T15:56:42.963Z | Explain Code | v2 | null | int write_inode(char *filename int index, char *name, int offset, int length) {
Inode inode;
FILE *fs = fopen(filenname, "r+");
strncpy(inode.name, name, MAXNAME);
inode.offset = offset;
inode.length = length;
if (fseek(fs, index * sizeof(Inode), SEEK_SET) == -1) {
perror("fseek");
return -1;
};
fwrite(&inode, sizeof(Inode), 1, fs);
return 0;
} | null | null |
63c647dc5f004bf4898cf752 | 2023-04-25T21:18:22.315Z | Explain Code | v2 | null | int main() {
pipe(fd);
int pid = fork();
if (pid == 0) {
close(fd[0]);
struct sigaction sa;
sa.sa_handler = send_one;
sa.sa_flags = 0;
sigemptyset(&sa.sa_mask);
sigaction(SIGUSR1, &sa, NULL);
while (1)
;
} else if (pid > 0) {
close(fd[1]);
int count = 0;
while (1) {
}
}
return 0;
} | null | null |
63c647dd5f004bf4898cf757 | 2023-01-18T02:17:19.605Z | Question from Code | v1 | why does it print nothing and exit when stdin gets -1? | #include <stdio.h>
int main() {
char phone[11];
int integer;
scanf("%s", phone);
scanf("%d", &integer);
while (integer != EOF) {
if (integer == -1) {
for (int i = 0; i < 10; i++) {
printf("%c", phone[i]);
}
printf("\n");
}
else if (integer > -1 && integer < 10) {
printf("%c\n", phone[integer]);
}
else {
printf("ERROR\n");
return 1;
}
scanf("%d", &integer);
}
return 0;
}
| null | null |
63c647dd5f004bf4898cf757 | 2023-03-12T23:14:49.758Z | Explain Code | v2 | null | Rule *curr = rules; // want to iterate to end of rules
while (curr->next_rule != NULL) {
curr = curr->next_rule;
} // curr->next_rule == NULL
curr->next_rule = new_rule; // insert new rule to end of rules | null | null |
63c647dd5f004bf4898cf757 | 2023-03-12T23:15:32.652Z | Help Fix Code | v2 | insert new rule to the end of rules | Rule *curr = rules; // want to iterate to end of rules
while (curr->next_rule != NULL) {
curr = curr->next_rule;
} // curr->next_rule == NULL
curr->next_rule = new_rule; // insert new rule to end of rules | null | null |
63c647dd5f004bf4898cf757 | 2023-03-12T23:16:35.012Z | Help Fix Code | v2 | insert new rule to end of rules | if (rules == NULL) {rules = new_rule;} // if rules == NULL, new_rule becomes first rule
else { // if rules != NULL
Rule *curr = rules; // want to iterate to end of rules
while (curr->next_rule != NULL) {
curr = curr->next_rule;
} // curr->next_rule == NULL
curr->next_rule = new_rule; // insert new rule to end of rules
} | null | null |
63c647dd5f004bf4898cf75c | 2023-01-24T05:55:41.783Z | Help Fix Code | v1 | null | char *ch = "S"; | null | null |
63c647dd5f004bf4898cf75c | 2023-01-24T05:56:14.498Z | General Question | v1 | Declare a char variable named ch and set its value to the first letter of your own name. | null | null | null |
63c647dd5f004bf4898cf75c | 2023-01-31T02:34:26.209Z | Explain Code | v1 | null | *delicious = "ice cream"; | null | null |
63c647dd5f004bf4898cf75c | 2023-01-31T02:34:50.028Z | General Question | v1 | Set the value of delicious (which has already been declared) to "ice cream". | null | null | null |
63c647dd5f004bf4898cf75c | 2023-01-31T02:42:01.806Z | General Question | v1 | The string sweet has been declared on the heap and has space for 20 characters.
Set the value of sweet to "tiramisu" without changing its address. | null | null | null |
63c647dd5f004bf4898cf75c | 2023-01-31T04:35:08.069Z | General Question | v1 | Create a node struct with the following struct members:
- value, an integer
- next, a pointer to another node | null | null | null |
63c647dd5f004bf4898cf75c | 2023-01-31T04:36:00.551Z | General Question | v1 | generate a detailed documentation of `typedef struct node {
int value;
struct node *next;
} node;` with usage examples and explanations | null | null | null |
63c647dd5f004bf4898cf75c | 2023-01-31T04:38:00.766Z | General Question | v1 | Write a loop which traverses a linked list starting at front and prints the value of each node in the list. | null | null | null |
63c647dd5f004bf4898cf75c | 2023-01-31T04:46:43.905Z | General Question | v1 | Which of these scenarios cause a memory leak? | null | null | null |
63c647dd5f004bf4898cf75c | 2023-01-31T04:58:03.503Z | General Question | v1 | Define a string literal called season that has the value
"winter".
Define a stack-allocated string called holiday that has space for 20 characters
including the null terminator. Set its initial value to "Valentine's Day". | null | null | null |
63c647dd5f004bf4898cf75c | 2023-01-31T04:59:28.764Z | General Question | v1 | The difference between stack-allocated string and heap-allocated string | null | null | null |
63c647dd5f004bf4898cf75c | 2023-02-13T23:14:00.074Z | Question from Code | v1 | What will be the output of the following program fragment?
|
#define SUPERVISOR(regular) regular + 5
int main() {
int regular_pay = 20;
int hours_worked = 10;
printf("pay is %d\n", (hours_worked * SUPERVISOR(regular_pay)));
// rest omitted
} | null | null |
63c647dd5f004bf4898cf75c | 2023-02-13T23:17:41.342Z | Question from Code | v1 | What is the line to compile it into an executable named a.out that it will print the value 5 to stdout? (You do not need to include the options to display warnings, build the symbol table for the debugger or select the C standard.) | #include <stdio.h>
int main() {
#ifdef MACRO
printf("%d\n", MACRO);
#endif
return 0;
} | null | null |
63c647dd5f004bf4898cf75c | 2023-02-13T23:19:00.695Z | 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? | null | null | null |
63c647dd5f004bf4898cf75c | 2023-02-13T23:35:25.970Z | General Question | v1 |
Which of the following functions are system calls?
exit()
fgets()
fopen()
printf()
read()
scanf()
write()
| null | null | null |
63c647dd5f004bf4898cf75c | 2023-02-13T23:35:55.272Z | General Question | v1 |
Which of the following functions are library calls?
exit()
fgets()
fopen()
printf()
read()
scanf()
write()
| null | null | null |
63c647dd5f004bf4898cf75c | 2023-02-13T23:44:25.704Z | Question from Code | v1 | What will this declaration line become after the program has passed
through the C pre-processor? | #define MAXNAME = 32;
char name[MAXNAME]; | null | null |
63c647dd5f004bf4898cf75c | 2023-02-13T23:53:31.008Z | Help Fix Code | v1 | null | #define MAXNAME = 32;
char name[MAXNAME]; | What will this declaration line become after the program has passed through the C pre-processor? | null |
63c647dd5f004bf4898cf75c | 2023-02-21T16:12:02.103Z | Help Fix Code | v1 | null | int update_pic(User *user, const char *filename) {
return -1;
} | /*
* Change the filename for the profile pic of the given user.
*
* Return:
* - 0 on success.
* - 1 if the file does not exist or cannot be opened.
* - 2 if the filename is too long.
*/ | null |
63c647dd5f004bf4898cf75c | 2023-02-21T16:42:09.073Z | Help Fix Code | v1 | null | int update_pic(User *user, const char *filename) {
if (strlen(filename) + 1 > MAX_NAME) {
return 2;
}
struct stat foo;
if (stat(filename, &foo) != 0) {
return 1;
}
strcpy(user->profile_pic, filename);
return 0;
} | /* * Change the filename for the profile pic of the given user. * * Return: * - 0 on success. * - 1 if the file does not exist or cannot be opened. * - 2 if the filename is too long. */ | null |
63c647dd5f004bf4898cf75c | 2023-02-21T16:47:35.270Z | Help Fix Code | v1 | null | int update_pic(User *user, const char *filename) {
if (strlen(filename) + 1 > MAX_NAME) {
return 2;
}
struct stat foo;
if (stat(filename, &foo) != 0) {
return 1;
}
strcpy(user->profile_pic, filename);
return 0;
} | /* * Change the filename for the profile pic of the given user. * * Return: * - 0 on success. * - 1 if the file does not exist or cannot be opened. * - 2 if the filename is too long. */
Has to be valid for C99 | null |
63c647dd5f004bf4898cf75c | 2023-02-21T19:32:58.156Z | Help Fix Code | v1 | null | int create_user(const char *name, User **user_ptr_add) {
if (strlen(name) >= MAX_NAME) {
return 2;
}
User *new_user = malloc(sizeof(User));
if (new_user == NULL) {
perror("malloc");
exit(1);
}
strncpy(new_user->name, name, MAX_NAME); // name has max length MAX_NAME - 1
for (int i = 0; i < MAX_NAME; i++) {
new_user->profile_pic[i] = '\0';
}
new_user->first_post = NULL;
new_user->next = NULL;
for (int i = 0; i < MAX_FRIENDS; i++) {
new_user->friends[i] = NULL;
}
// Add user to list
User *prev = NULL;
User *curr = *user_ptr_add;
while (curr != NULL && strcmp(curr->name, name) != 0) {
prev = curr;
curr = curr->next;
}
if (prev == NULL) {
*user_ptr_add = new_user;
return 0;
} else if (curr != NULL) {
free(new_user);
return 1;
} else {
prev->next = new_user;
return 0;
}
} | /*
* Create a new user with the given name. Insert it at the tail of the list
* of users whose head is pointed to by *user_ptr_add.
*
* Return:
* - 0 if successful
* - 1 if a user by this name already exists in this list
* - 2 if the given name cannot fit in the 'name' array
* (don't forget about the null terminator)
*/ | null |
63c647dd5f004bf4898cf75c | 2023-02-21T19:36:59.787Z | Explain Code | v1 | null | int create_user(const char *name, User **user_ptr_add) {
if (strlen(name) >= MAX_NAME) {
return 2;
}
User *new_user = malloc(sizeof(User));
if (new_user == NULL) {
perror("malloc");
exit(1);
}
strncpy(new_user->name, name, MAX_NAME); // name has max length MAX_NAME - 1
for (int i = 0; i < MAX_NAME; i++) {
new_user->profile_pic[i] = '\0';
}
new_user->first_post = NULL;
new_user->next = NULL;
for (int i = 0; i < MAX_FRIENDS; i++) {
new_user->friends[i] = NULL;
}
// Add user to list
User *prev = NULL;
User *curr = *user_ptr_add;
while (curr != NULL && strcmp(curr->name, name) != 0) {
prev = curr;
curr = curr->next;
}
if (prev == NULL) {
*user_ptr_add = new_user;
return 0;
} else if (curr != NULL) {
free(new_user);
return 1;
} else {
prev->next = new_user;
return 0;
}
} | null | null |
63c647dd5f004bf4898cf75c | 2023-02-21T21:36:22.659Z | Help Fix Code | v1 | null | User *find_user(const char *name, const User *head) {
for (User *ptr = (User *)head; ptr != NULL; ptr = ptr->next) {
if (strcmp(ptr->name, name) == 0) {
return ptr;
}
}
return NULL;
} | /*
* Return a pointer to the user with this name in
* the list starting with head. Return NULL if no such user exists.
*
* NOTE: You'll likely need to cast a (const User *) to a (User *)
* to satisfy the prototype without warnings.
*/ | null |
63c647dd5f004bf4898cf75c | 2023-02-21T21:49:11.616Z | Explain Code | v1 | null | User *find_user(const char *name, const User *head) {
for (User *ptr = (User *)head; ptr != NULL; ptr = ptr->next) {
if (strcmp(ptr->name, name) == 0) {
return ptr;
}
}
return NULL;
} | null | null |
63c647dd5f004bf4898cf75c | 2023-02-22T18:59:54.627Z | Help Fix Code | v1 | null | while (strcmp(curr->name, name) && curr != NULL != 0) {
prev = curr;
curr = curr->next;
} | *
iterates through the linked list until curr is NULL or the
name field of curr is equal to the string
*/ | null |
63c647dd5f004bf4898cf75c | 2023-02-22T20:59:15.488Z | Explain Code | v1 | null | void printPicture(const User *user) {
//if they have no profile picture we can just return since there is nothing
//to print at all.
if (strlen(user->profile_pic) <= 0) {
return;
}
//continues onward because there is something that is larger than 0,
//in the profile pic object.
FILE *picture = fopen(user->profile_pic, "r");
int edpoint;
char printBuffer[1023];
while (fgets(printBuffer, 1023, picture) != NULL) {
edpoint = strlen(printBuffer) - 1;
if (printBuffer[edpoint] == '\n') {
printBuffer[edpoint] = '\0';
}
printEntry(printBuffer);
}
fclose(picture);
} | null | null |
63c647dd5f004bf4898cf75c | 2023-02-22T21:07:39.103Z | Help Fix Code | v1 | null | void printPicture(const User *user) {
//if they have no profile picture we can just return since there is nothing
//to print at all.
if (strlen(user->profile_pic) <= 0) {
return;
}
//continues onward because there is something that is larger than 0,
//in the profile pic object.
FILE *picture = fopen(user->profile_pic, "r");
int edpoint;
char printBuffer[1023];
while (fgets(printBuffer, 1023, picture) != NULL) {
edpoint = strlen(printBuffer) - 1;
//checks if the last character of the string in printBuffer is a newline
if (printBuffer[edpoint] == '\n') {
/*replaces the last character of the string
in printBuffer with a null character*/
printBuffer[edpoint] = '\0';
}
//prints the string in printBuffer
printEntry(printBuffer);
}
//close the file
fclose(picture);
}
/*Helper function that deletes all of the posts for a user and thenfrees all of
the memory for the all posts for that user*/
void removePosts(Post *post) {
//if the user has no posts then return because there is nothing to free.
if (!post) {
return;
}
//recursive function until we run out of posts to free.
removePosts(post->next);
//free the memory for the contents of the posts
free(post->contents);
free(post);
} | remove all the posts in the linked list. | null |
63c647dd5f004bf4898cf75c | 2023-02-22T21:09:11.051Z | Explain Code | v1 | null | void removePosts(Post *post) {
//if the user has no posts then return because there is nothing to free.
if (!post) {
return;
}
//recursive function until we run out of posts to free.
removePosts(post->next);
//free the memory for the contents of the posts
free(post->contents);
free(post);
} | null | null |
63c647dd5f004bf4898cf75c | 2023-02-22T21:26:56.080Z | Explain Code | v1 | null | /*Purges the user from the friends list of all users in the targets list.*/
void unAddfriend(User *exiledFriend, const User *user) {
if (!exiledFriend) {
return;
}
int difference, iterator = 0;
for (iterator = 0; iterator < MAX_FRIENDS &&
exiledFriend->friends[iterator]; iterator++) {
if (exiledFriend->friends[iterator] == user) {
difference++;
}
if (iterator + difference < MAX_FRIENDS) {
exiledFriend->friends[iterator] =
exiledFriend->friends[iterator + difference];
} else {
exiledFriend->friends[iterator] = NULL;
}
}
unAddfriend(exiledFriend->next, user);
} | null | null |
63c647dd5f004bf4898cf75c | 2023-02-22T21:39:36.065Z | Explain Code | v1 | null | int make_friends(const char *name1, const char *name2, User *head) {
int friendstatus = 0;
User *friendo1 = find_user(name1, head);
User *friendo2 = find_user(name2, head);
if (friendo1 == NULL || friendo2 == NULL) {
friendstatus = 4;
} else if (friendo1 == friendo2) {
friendstatus = 3;
}
int a;
for (a = 0; a < MAX_FRIENDS; a++) {
if (friendo1->friends[a] == NULL) {
break;
} else if (friendo1->friends[a] == friendo2) {
friendstatus = 1;
}
}
int b;
for (b = 0; b < MAX_FRIENDS; b++) {
if (friendo2->friends[b] == NULL) {
break;
}
}
if (a == MAX_FRIENDS || b == MAX_FRIENDS) {
friendstatus = 2;
}
friendo1->friends[a] = friendo2;
friendo2->friends[b] = friendo1;
return friendstatus;
} | null | null |
63c647dd5f004bf4898cf75c | 2023-02-22T21:55:55.866Z | Help Fix Code | v1 | null | int difference, iterator = 0; | initialise two variables with the same initial value. | null |
63c647dd5f004bf4898cf75c | 2023-02-22T22:21:20.523Z | Explain Code | v1 | null | int make_post(const User *author, User *target, char *contents) {
if (target == NULL || author == NULL) {
return 2;
}
int friends = 0;
for (int i = 0; i < MAX_FRIENDS && target->friends[i] != NULL; i++) {
if (strcmp(target->friends[i]->name, author->name) == 0) {
friends = 1;
break;
}
}
if (friends == 0) {
return 1;
}
// Create post
Post *new_post = malloc(sizeof(Post));
if (new_post == NULL) {
perror("malloc");
exit(1);
}
strncpy(new_post->author, author->name, MAX_NAME);
new_post->contents = contents;
new_post->date = malloc(sizeof(time_t));
if (new_post->date == NULL) {
perror("malloc");
exit(1);
}
time(new_post->date);
new_post->next = target->first_post;
target->first_post = new_post;
return 0;
} | null | null |
63c647dd5f004bf4898cf75c | 2023-02-22T22:22:11.690Z | Help Fix Code | v1 | null | int make_post(const User *author, User *target, char *contents) {
if (target == NULL || author == NULL) {
return 2;
}
int friends = 0;
for (int i = 0; i < MAX_FRIENDS && target->friends[i] != NULL; i++) {
if (strcmp(target->friends[i]->name, author->name) == 0) {
friends = 1;
break;
}
}
if (friends == 0) {
return 1;
}
// Create post
Post *new_post = malloc(sizeof(Post));
if (new_post == NULL) {
perror("malloc");
exit(1);
}
strncpy(new_post->author, author->name, MAX_NAME);
new_post->contents = contents;
new_post->date = malloc(sizeof(time_t));
if (new_post->date == NULL) {
perror("malloc");
exit(1);
}
time(new_post->date);
new_post->next = target->first_post;
target->first_post = new_post;
return 0;
} | /*
* Make a new post from 'author' to the 'target' user,
* containing the given contents, IF the users are friends.
*
* Insert the new post at the *front* of the user's list of posts.
*
* 'contents' is a pointer to heap-allocated memory - you do not need
* to allocate more memory to store the contents of the post.
*
* Return:
* - 0 on success
* - 1 if users exist but are not friends
* - 2 if either User pointer is NULL
*/
| null |
63c647dd5f004bf4898cf75c | 2023-02-22T22:25:31.705Z | Help Fix Code | v1 | null | int make_post(const User *author, User *target, char *contents) {
if (target == NULL || author == NULL) {
return 2;
}
int friends = 0;
for (int i = 0; i < MAX_FRIENDS && target->friends[i] != NULL; i++) {
if (strcmp(target->friends[i]->name, author->name) == 0) {
friends = 1;
break;
}
}
if (friends == 0) {
return 1;
}
// Create post
Post *new_post = malloc(sizeof(Post));
if (new_post == NULL) {
perror("malloc");
exit(1);
}
strncpy(new_post->author, author->name, MAX_NAME);
new_post->contents = contents;
new_post->date = malloc(sizeof(time_t));
if (new_post->date == NULL) {
perror("malloc");
exit(1);
}
time(new_post->date);
target->first_post = new_post;
new_post->next = target->first_post;
return 0;
} | /* * Make a new post from 'author' to the 'target' user, * containing the given contents, IF the users are friends. * * Insert the new post at the *front* of the user's list of posts. * * 'contents' is a pointer to heap-allocated memory - you do not need * to allocate more memory to store the contents of the post. * * Return: * - 0 on success * - 1 if users exist but are not friends * - 2 if either User pointer is NULL */
| null |
63c647dd5f004bf4898cf75c | 2023-02-22T23:06:52.061Z | Help Fix Code | v1 | null | int make_post(const User *author, User *target, char *contents) | Make a new post from 'author' to the 'target' user, * containing the given contents, IF the users are friends. * * Insert the new post at the *front* of the user's list of posts. * * 'contents' is a pointer to heap-allocated memory - you do not need * to allocate more memory to store the contents of the post. * * Return: * - 0 on success * - 1 if users exist but are not friends * - 2 if either User pointer is NULL */ | null |
63c647dd5f004bf4898cf75c | 2023-02-22T23:07:45.964Z | Help Fix Code | v1 | null | int make_post(const User *author, User *target, char *contents)
{
if (target == NULL || author == NULL)
{
return 2;
}
int friends = 0;
for (int i = 0; i < MAX_FRIENDS && target->friends[i] != NULL; i++)
{
if (strcmp(target->friends[i]->name, author->name) == 0)
{
friends = 1;
break;
}
}
if (friends == 0)
{
return 1;
}
/*Creating a post. allocates memory for a post and stores the address in
new_post */
Post *newlyPosted = malloc(sizeof(Post));
//checks if new post is NULL.
if (newlyPosted == NULL)
{
perror("malloc couldn't allocate memory");
exit(1);
}
strncpy(newlyPosted->author, author->name, MAX_NAME);
newlyPosted->contents = contents;
newlyPosted->date = malloc(sizeof(time_t));
if (newlyPosted->date == NULL)
{
perror("malloc couldn't allocate memory");
exit(1);
}
time(newlyPosted->date);
//newlyPosted->next = target->first_post;
//target->first_post = newlyPosted;
target->first_post = newlyPosted;
return 0;
} | Make a new post from 'author' to the 'target' user, * containing the given contents, IF the users are friends. * * Insert the new post at the *front* of the user's list of posts. * * 'contents' is a pointer to heap-allocated memory - you do not need * to allocate more memory to store the contents of the post. * * Return: * - 0 on success * - 1 if users exist but are not friends * - 2 if either User pointer is NULL */ | null |
63c647dd5f004bf4898cf75c | 2023-02-22T23:09:39.431Z | Help Fix Code | v1 | null | int make_post(const User *author, User *target, char *contents)
{
if (target == NULL || author == NULL)
{
return 2;
}
int friends = 0;
for (int i = 0; i < MAX_FRIENDS && target->friends[i] != NULL; i++)
{
if (strcmp(target->friends[i]->name, author->name) == 0)
{
friends = 1;
break;
}
}
if (friends == 0)
{
return 1;
}
/*Creating a post. allocates memory for a post and stores the address in
new_post */
Post *newlyPosted = malloc(sizeof(Post));
//checks if new post is NULL.
if (newlyPosted == NULL)
{
perror("malloc couldn't allocate memory");
exit(1);
}
strncpy(newlyPosted->author, author->name, MAX_NAME);
newlyPosted->contents = contents;
newlyPosted->date = malloc(sizeof(time_t));
if (newlyPosted->date == NULL)
{
perror("malloc couldn't allocate memory");
exit(1);
}
time(newlyPosted->date);
newlyPosted->next = target->first_post;
target->first_post = newlyPosted;
return 0;
} | Make a new post from 'author' to the 'target' user, * containing the given contents, IF the users are friends. * * Insert the new post at the *front* of the user's list of posts. * * 'contents' is a pointer to heap-allocated memory - you do not need * to allocate more memory to store the contents of the post. * * Return: * - 0 on success * - 1 if users exist but are not friends * - 2 if either User pointer is NULL */ | null |
63c647dd5f004bf4898cf75c | 2023-02-22T23:12:11.647Z | Explain Code | v1 | null | int make_post(const User *author, User *target, char *contents)
{
if (target == NULL || author == NULL)
{
return 2;
}
int friends = 0;
for (int i = 0; i < MAX_FRIENDS && target->friends[i] != NULL; i++)
{
if (strcmp(target->friends[i]->name, author->name) == 0)
{
friends = 1;
break;
}
}
if (friends == 0)
{
return 1;
}
/*Creating a post. allocates memory for a post and stores the address in
new_post */
Post *newlyPosted = malloc(sizeof(Post));
//checks if new post is NULL.
if (newlyPosted == NULL)
{
perror("malloc couldn't allocate memory");
exit(1);
}
strncpy(newlyPosted->author, author->name, MAX_NAME);
newlyPosted->contents = contents;
newlyPosted->date = malloc(sizeof(time_t));
if (newlyPosted->date == NULL)
{
perror("malloc couldn't allocate memory");
exit(1);
}
time(newlyPosted->date);
newlyPosted->next = target->first_post;
target->first_post = newlyPosted;
return 0;
} | null | null |
63c647dd5f004bf4898cf75c | 2023-02-28T02:29:04.856Z | General Question | v1 | Select the sentence fragments that complete this sentence so that it is true.
When one process forks another:
the process that calls fork is called the parent and the newly-created process is the child.
the code segments of the two processes are identical.
the values of all the variables of the two processes are identical.
the two processes have all the same variables but each process has its own copy and the return value from the fork system call is different for the two processes because in each case it is set to the other's PID.
the operating system determines which of the two process gets to execute first.
the two process are siblings. | null | null | null |
63c647dd5f004bf4898cf75c | 2023-02-28T02:30:25.810Z | General Question | v1 | A parent process with pid 1123 forks a child process with pid 1126. In the child process, what is the return value of fork()?
| null | null | null |
63c647dd5f004bf4898cf75c | 2023-02-28T02:30:56.002Z | General Question | v1 | A parent process with pid 1123 forks a child process with pid 1126. In the parent process, what is the return value of fork()? | null | null | null |
63c647dd5f004bf4898cf75c | 2023-02-28T02:32:29.078Z | General Question | v1 | On teach.cs, you can run man 2 wait to learn about the wait system call. Which macro is used with wait's status to check if the child process was terminated by a signal? | null | null | null |
63c647dd5f004bf4898cf75c | 2023-03-03T02:59:42.533Z | Explain Code | v1 | null | #include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
int main(int argc, char **argv) {
int iterations;
if (argc != 2) {
fprintf(stderr, "Usage: forkloop <iterations>\n");
exit(1);
}
//Get the parent id
int parentPID = getpid();
iterations = strtol(argv[1], NULL, 10);
for (int loopval; = 0; loopval < iterations; loopval++) {
//Only fork if the PID matches the parent PID
if (getpid() == parentPID){
int n = fork();
if (n < 0) {
perror("fork");
exit(1);
}
}
printf("ppid = %d, pid = %d, i = %d\n", getppid(), getpid(), i);
}
return 0;
} | null | null |
63c647dd5f004bf4898cf75c | 2023-03-03T03:06:47.983Z | Explain Code | v1 | null | #include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
int main(int argc, char **argv) {
//iterations is an integer that stores
//the number of iterations the program will run
int loopval, iterations;
if (argc != 2) {
fprintf(stderr, "Usage: forkloop <iterations>\n");
exit(1);
}
int forked;
//iterations is set to the integer representation of the
//command line argument (the second element of the array argv)
iterations = strtol(argv[1], NULL, 10);
for (loopval = 0; loopval < iterations;
loopval++) {
//Fork once for the parent
if(loopval == 0){
forked = fork();
if(forked < 0) {
perror("fork");
exit(1);
}
}
else{
//Fork once per child
if(forked == 0){
forked = fork();
if(forked < 0) {
perror("fork");
exit(1);
}
}
}
printf("ppid = %d, pid = %d, i = %d\n", getppid(), getpid(), i);
}
return 0;
} | null | null |
63c647dd5f004bf4898cf75c | 2023-03-03T03:27:32.750Z | Explain Code | v1 | null | #include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/wait.h>
int main(int argc, char **argv) {
int iterations, loopval, status;
if (argc != 2) {
fprintf(stderr, "Usage: forkloop <iterations>\n");
exit(1);
}
iterations = strtol(argv[1], NULL, 10);
for (loopval = 0; loopval < iterations;
loopval++) {
int forkedval = fork();
if (forkedval < 0) {
perror("fork");
exit(1);
} else if (forkedval == 0){
loopval = iterations;
} else {
wait(&status);
}
printf("ppid = %d, pid = %d, i = %d\n", getppid(), getpid(), i);
}
return 0;
} | null | null |
63c647dd5f004bf4898cf75c | 2023-03-03T03:31:35.912Z | Explain Code | v1 | null | #include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/wait.h>
int main(int argc, char **argv) {
int iterations, loopval, status;
if (argc != 2) {
fprintf(stderr, "Usage: forkloop <iterations>\n");
exit(1);
}
iterations = strtol(argv[1], NULL, 10);
for (loopval = 0; loopval < iterations;
loopval++) {
int forkedval = fork();
if (forkedval < 0) {
perror("fork");
exit(1);
} else if (n > 0){
loopval = iterations;
wait(&status);
}
printf("ppid = %d, pid = %d, i = %d\n", getppid(), getpid(), i);
}
return 0;
} | null | null |
63c647dd5f004bf4898cf75c | 2023-03-10T00:11:53.779Z | Help Fix Code | v1 | null | #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
*/
if(fgets(user_id, MAXLINE, stdin) == NULL) {
perror("fgets");
exit(1);
}
if(fgets(password, MAXLINE, stdin) == NULL) {
perror("fgets");
exit(1);
}
// pipe
int fd[2];
if (pipe(fd) < 0) {
perror("pipe");
exit(1);
}
// fork
pid_t pid = fork();
if (pid == -1) {
perror("fork");
exit(1);
}
// parent
if (pid > 0) {
// close the read end of the pipe for parent
if (close(fd[0]) == -1) {
perror("close");
exit(1);
}
// write user and pass to pipe
if (write(fd[1], user_id, strlen(user_id)) == -1) {
perror("write");
exit(1);
}
if (write(fd[1], password, strlen(password)) == -1) {
perror("write");
exit(1);
}
if (close(fd[1]) == -1) { // close the write pipe
perror("close");
exit(1);
}
}
else {
// close the write end of the pipe for child
if (close(fd[1]) == -1) {
perror("close");
exit(1);
}
// redirect stdin of child process to come from pipe
if (dup2(fd[0], STDIN_FILENO) == -1) {
perror("dup2");
exit(1);
}
// close file descriptors
if (close(fd[0]) == -1) {
perror("close");
exit(1);
}
// execute validate
execl("./validate", "validate", NULL);
perror("execl");
exit(1);
}
int status;
// use child to verify user
wait(&status);
if (WIFEXITED(status)) {
int exit_code = WEXITSTATUS(status);
switch(exit_code) {
case 0:
printf(SUCCESS);
break;
case 2:
printf(INVALID);
break;
case 3:
printf(NO_USER);
break;
}
}
return 0;
}
| This is a C program that prompts the user to enter a user ID and password, passes them to a child process through a pipe, and uses the child process to validate the user's credentials by executing a separate program called "validate".
The program reads the user ID and password from standard input using the fgets function, and stores them in the user_id and password variables respectively.
It then creates a pipe using the pipe system call to establish a unidirectional communication channel between the parent and child processes.
Next, it forks a child process using the fork system call, which creates a copy of the parent process. The parent process writes the user ID and password to the write end of the pipe, and the child process reads from the read end of the pipe.
The child process redirects its standard input to read from the read end of the pipe using the dup2 system call, and then executes the "validate" program using the execl system call.
The "validate" program reads the user ID and password from standard input and validates them against a database of user credentials. It returns an exit code to indicate whether the user credentials are valid or not.
The parent process waits for the child process to terminate using the wait system call, and then checks the exit code returned by the child process. Depending on the exit code, it prints one of three possible messages to standard output: "Password verified", "Invalid password", or "No such user".
Finally, the program returns 0 to indicate successful execution.
Some of the improvements made to the original code include adding comments to explain the purpose of each section of code, removing unnecessary header files, defining constants for the possible output messages, and improving error handling by checking the return values of system calls and printing error messages when necessary. | null |
63c647dd5f004bf4898cf75c | 2023-03-13T23:35:23.016Z | Question from Code | v2 | Assume the following program which compiles and runs without error.
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 ");
// 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;
} | null | null |
63c647dd5f004bf4898cf75c | 2023-03-13T23:40:00.268Z | Question from Code | v2 | Assume the following code runs without error. | 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;
} | null | null |
63c647dd5f004bf4898cf75c | 2023-03-27T21:41:58.169Z | General Question | v2 | Variable x has been assigned a digit between 1 and 10. Write a shell command to calculate x minus 1 and display the result to standard output.
| null | null | null |
63c647dd5f004bf4898cf75c | 2023-03-27T21:44:18.560Z | General Question | v2 | Variables width and height have been initialized. Calculate the area of a rectangle using width and height, and assign the resulting value to a variable named area. | null | null | null |
63c647e15f004bf4898cf77a | 2023-01-17T20:56:39.598Z | General Question | v1 | what is string in C? | null | null | null |
63c647e25f004bf4898cf77f | 2023-02-01T06:20:00.414Z | General Question | v1 | what is the error "zsh: trace trap"
| null | null | null |
63c647e25f004bf4898cf77f | 2023-02-16T16:32:06.332Z | General Question | v1 | What is the memset syntax? | null | null | null |
63c647e55f004bf4898cf798 | 2023-01-17T20:14:54.732Z | Help Fix Code | v1 | null | void swapA(int *num1, int *num2) {
int *temp = num1;
num1 = num2;
num2 = temp;
} | swap num1 and num2 | null |
63c647e55f004bf4898cf798 | 2023-01-17T20:16:07.998Z | Explain Code | v1 | null | void swapA(int *num1, int *num2) {
int *temp = num1;
num1 = num2;
num2 = temp;
} | null | null |
63c647e65f004bf4898cf79d | 2023-01-22T21:29:16.935Z | Explain Code | v1 | null | #include <stdio.h>
int main() {
printf("Hello, World!\n");
return 0;
}
| null | null |
63c647e65f004bf4898cf79d | 2023-02-02T00:42:57.663Z | Explain Code | v1 | null | int main() {
// Declare a struct faculty named p1.
struct faculty p1;
// Initialize p1 to represent Professor Roger Grosse, whose research area
// is ML (Machine Learning). He is supervising 11 graduate students.
p1.name = "Professor Roger Grosse";
strcpy(pl.area, "ML");
pl.num_students = 11;
struct faculty *p2_pt;
// allocate space for the faculty on the heap
p2_pt = malloc(sizeof(struct faculty));
// Error checking
if (p2_pt == NULL) {
perror("malloc"); //look at perror documentation
return 1;
}
// Set the values of *p2_pt to represent Professor Sheila McIlraith. Her research area
// is KR (Knowledge Representation). She is supervising 5 graduate students.
p2_pt->name = "Professor Sheila McIlraith";
strcpy(p2_pt->area, "KR");
p2_pt->num_students = 5;
return 0;
} | null | null |
63c647e65f004bf4898cf79d | 2023-02-12T16:13:25.938Z | General Question | v1 | how to get a human-readable representation of the date and time of each post in the format, "Friday Jan 27 23:01:00 2023" using time and ctime functions? | null | null | null |
63c647e65f004bf4898cf79d | 2023-02-12T16:56:25.479Z | General Question | v1 | generate a detailed documentation of `time` with usage examples and explanations | null | null | null |
63c647e65f004bf4898cf79d | 2023-02-12T17:00:15.238Z | General Question | v1 | Why is time and ctime not giving me the current time but an arbitrary time? | null | null | null |
63c647e65f004bf4898cf79d | 2023-02-12T17:04:38.663Z | General Question | v1 | generate a detailed documentation of `time` with usage examples and explanations | null | null | null |
63c647e65f004bf4898cf79d | 2023-02-12T17:05:36.221Z | General Question | v1 | how do I use time to get the current time? Not the time since epoch? | null | null | null |
63c647e65f004bf4898cf79d | 2023-03-13T01:36:22.061Z | General Question | v2 | how to use stat? | null | null | null |
63c647e65f004bf4898cf7a2 | 2023-01-17T15:09:44.024Z | General Question | v1 | how do I append to a list in C? | null | null | null |
63c647e85f004bf4898cf7b1 | 2023-01-17T23:47:08.392Z | Question from Code | v1 | what does this do?
| char *result[2]; | null | null |
63c647e85f004bf4898cf7b1 | 2023-01-17T23:47:59.799Z | Question from Code | v1 | can you show me a visual representation?
| char *result[2];
| null | null |
63c647e85f004bf4898cf7b1 | 2023-02-10T21:56:06.541Z | Explain Code | v1 | null | struct pixel **pixels = read_pixel_array(image, pixel_array_offset, width, height); | null | null |
63c647e85f004bf4898cf7b1 | 2023-02-10T21:59:22.720Z | Question from Code | v1 | So the result is a pixel struct, where each strcuts is apointer? | struct pixel **pixels = read_pixel_array(image, pixel_array_offset, width, height); | null | null |
63c647e85f004bf4898cf7b1 | 2023-02-10T22:12:15.212Z | General Question | v1 | how to allocate space on stack for many values?
| null | null | null |
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