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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
⌀ |
|---|---|---|---|---|---|---|---|
63c647ae5f004bf4898cf5c7 | 2023-04-25T16:43:51.265Z | General Question | v2 | Could I dereference out-of-bound index? | null | null | null |
63c647ae5f004bf4898cf5c7 | 2023-04-25T16:46:07.496Z | General Question | v2 | How to check if a binary representation is a negative number? | null | null | null |
63c647ae5f004bf4898cf5c7 | 2023-04-25T16:47:08.421Z | General Question | v2 | Where is the sign bit in binary representation? | null | null | null |
63c647ae5f004bf4898cf5c7 | 2023-04-25T16:51:15.112Z | General Question | v2 | How to copy an array of characters? | null | null | null |
63c647ae5f004bf4898cf5c7 | 2023-04-25T18:46:09.642Z | General Question | v2 | redir in shell programming? | null | null | null |
63c647ae5f004bf4898cf5c7 | 2023-04-25T20:40:40.188Z | General Question | v2 | When to update max_fd in socket programming? | null | null | null |
63c647ae5f004bf4898cf5c7 | 2023-04-25T20:42:35.780Z | General Question | v2 | What happens if I initialized the members of a struct with values in a wrong way? | null | null | null |
63c647ae5f004bf4898cf5c7 | 2023-04-25T20:49:48.361Z | General Question | v2 | Name the three (3) categories that most preprocessing directives fall into | null | null | null |
63c647ae5f004bf4898cf5c7 | 2023-04-25T20:51:23.117Z | General Question | v2 | What are the three categories most of C preprocessors are categorized as? | null | null | null |
63c647ae5f004bf4898cf5c7 | 2023-04-25T20:52:26.538Z | General Question | v2 | What is the point of calling fclose() when program will end anyway? | null | null | null |
63c647ae5f004bf4898cf5c7 | 2023-04-25T20:53:28.246Z | General Question | v2 | What are 2 similarities between pipes and files? | null | null | null |
63c647ae5f004bf4898cf5c7 | 2023-04-25T20:58:34.899Z | General Question | v2 | How do I initialize an array of char? | null | null | null |
63c647ae5f004bf4898cf5c7 | 2023-04-25T21:08:01.342Z | General Question | v2 | How to identify if a process is a zombie? | null | null | null |
63c647ae5f004bf4898cf5c7 | 2023-04-25T21:09:20.324Z | General Question | v2 | What does ps aux do? | null | null | null |
63c647ae5f004bf4898cf5c7 | 2023-04-25T21:09:58.879Z | General Question | v2 | How does ps differ from ps aux? | null | null | null |
63c647ae5f004bf4898cf5c7 | 2023-04-25T21:12:22.305Z | General Question | v2 | Are System calls C programs' interface to the operating system and the computer’s hardware? | null | null | null |
63c647ae5f004bf4898cf5c7 | 2023-04-25T21:13:16.832Z | General Question | v2 | Is it true that a server may read and write to multiple clients on the same socket? | null | null | null |
63c647ae5f004bf4898cf5c7 | 2023-04-25T21:15:12.207Z | General Question | v2 | Is it true that Makefile will exit with an error if the target of a rule is not a file? | null | null | null |
63c647ae5f004bf4898cf5c7 | 2023-04-25T21:15:57.853Z | General Question | v2 | Are all dependencies in a Makefile files? | null | null | null |
63c647b05f004bf4898cf5d6 | 2023-01-19T02:45:07.072Z | Help Fix Code | v1 | null | char phone[11];
int num;
scanf("%s%d", phone, num); | phone should save the first 11 char from the input, which is followed by a number | null |
63c647b05f004bf4898cf5d6 | 2023-01-22T23:54:23.456Z | Explain Code | v1 | null | int length = 0;
int num = 298475
for (int i = 10; i > 10; i*10) {
num -= (num % i);
length ++
} | null | null |
63c647b05f004bf4898cf5d6 | 2023-01-23T00:06:33.860Z | Explain Code | v1 | null | int c = 1;
int a = c; | null | null |
63c647b05f004bf4898cf5d6 | 2023-01-23T00:11:51.745Z | Explain Code | v1 | null | int x = 123;
if (x / 10 == 12){
printf("yay");
} | null | null |
63c647b05f004bf4898cf5d6 | 2023-01-23T00:12:41.562Z | Explain Code | v1 | null | int x = 128;
if (x / 10 == 12){
printf("yay");
} | null | null |
63c647b05f004bf4898cf5d6 | 2023-01-28T02:23:10.331Z | Help Fix Code | v1 | null | int copy = 123456789;
int length = 1;
for (int i = 10; copy > 10; i * 10){
copy -= copy % i; // turning every digit to 0
length += 1;
} | count the number of digits in copy | null |
63c647b05f004bf4898cf5d6 | 2023-01-28T03:03:19.327Z | Explain Code | v1 | null | printf("check: %d \n", sin % (10^1)); | null | null |
63c647b05f004bf4898cf5d6 | 2023-01-28T03:03:46.784Z | Explain Code | v1 | null | printf("check: %d \n", 123456789 % (10^1)); | null | null |
63c647b05f004bf4898cf5d6 | 2023-01-28T03:05:38.961Z | Explain Code | v1 | null | int sin = 123456789;
for (int i = 0; i < 9; i ++) {
printf("sin: %d \n", sin);
int digit = (sin % (10^(1+i)));
printf("digit: %d \n", digit);
sin -= digit * 10^i;
sin_array[8 - i] = digit // dividing by 10 drops the decimals
printf("array: %d \n", sin_array[8 - i]);
} | null | null |
63c647b05f004bf4898cf5d6 | 2023-01-28T03:10:24.036Z | Explain Code | v1 | null | int sin = 123456789;
for (int i = 0; i < 9; i ++) {
printf("sin: %d \n", sin);
int digit = (sin % (10^(1+i)));
printf("digit: %d \n", digit);
sin -= digit * 10^i;
sin_array[8 - i] = digit; // dividing by 10 drops the decimals
printf("array: %d \n", sin_array[8 - i]);
} | null | null |
63c647b05f004bf4898cf5d6 | 2023-01-28T03:17:52.627Z | Help Fix Code | v1 | null |
#include <stdio.h>
#include <stdlib.h>
int main()
{
int sin = 123456789;
int sin_array[9];
int digit;
for (int i = 0; i < 9; i ++) {
digit = sin % (10^(1+i));
printf("digit: %d \n", digit);
sin -= digit * 10^i;
sin = sin / 10;
sin_array[8 - i] = digit;
}
} | should take each digit in sin and place it in sin_array at the corresponding index | null |
63c647b05f004bf4898cf5d6 | 2023-01-31T20:09:08.521Z | Help Fix Code | v1 | null | if (strlen(str) > amount) {
// truncate str at amount characters
str[amount] = '\0';
return (strlen(str) - amount);
}
return 0; | if length of the string is greater than the amount given, then truncate the string to be of length amount and return the number of chars removed | null |
63c647b05f004bf4898cf5d6 | 2023-02-09T20:05:16.989Z | Help Fix Code | v1 | null | struct *current;
int length = sizeof(*(current->friends))/sizeof(*(current->friends)[0]);
| save length of an array called friends that's saved in struct called current | null |
63c647b05f004bf4898cf5d6 | 2023-02-11T05:55:45.518Z | 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? | #include <stdio.h>
int main() {
#ifdef MACRO
printf("%d\n", MACRO);
#endif
return 0;
}
| null | null |
63c647b05f004bf4898cf5d6 | 2023-02-11T05:57:09.215Z | Question from Code | v1 | in the program. What will this declaration line become after the program has passed through the C pre-processor? | #define MAXNAME = 32;
char name[MAXNAME];
| null | null |
63c647b05f004bf4898cf5d6 | 2023-02-27T16:13:32.016Z | Question from Code | v1 | why does the third line make w[1] = "ello"? | char **w = malloc(2 * sizeof(char *));
w[0] = "hello";
*(w + 1) = w[0] + 1;
printf("%s, %s", w[0], w[1]); | null | null |
63c647b05f004bf4898cf5d6 | 2023-02-27T16:17:11.200Z | General Question | v1 | how can you tell the difference between compiling and run time error
| null | null | null |
63c647b05f004bf4898cf5d6 | 2023-02-27T16:20:29.923Z | Explain Code | v1 | null | char *names[2]; | null | null |
63c647b05f004bf4898cf5d6 | 2023-02-27T16:21:39.230Z | Question from Code | v1 | which takes precedence, * or [2] | char *names[2]; | null | null |
63c647b05f004bf4898cf5d6 | 2023-02-27T16:23:19.240Z | General Question | v1 | fscanf vs fread? | null | null | null |
63c647b05f004bf4898cf5d6 | 2023-02-27T16:27:14.577Z | Question from Code | v1 | is this run time or compiling error | char *film = "Moonlight"; NO ERROR
char x;
x = film; RUN-TIME ERROR
x[0] = ’L’; | null | null |
63c647b05f004bf4898cf5d6 | 2023-02-27T16:27:40.912Z | Question from Code | v1 | is this run time or compiling error | char *film = "Moonlight";
char x;
x = film;
x[0] = ’L’; | null | null |
63c647b05f004bf4898cf5d6 | 2023-02-27T16:35:14.609Z | Question from Code | v1 | why is this a run time error | int *mkpoint(int x, int y) {
int pt[2] = {x, y};
return pt;
}
int *x;
x = mkpoint(3, 4); | null | null |
63c647b05f004bf4898cf5d6 | 2023-02-27T20:11:33.357Z | Question from Code | v1 | how do we make sure the new children don't create additional processes | for (int i = 0; i < iterations; i++) {
int n = fork();
if (n < 0) {
perror("fork");
exit(1);
}
printf("ppid = %d, pid = %d, i = %d\n", getppid(), getpid(), i);
}
| null | null |
63c647b05f004bf4898cf5d6 | 2023-02-27T21:34:30.308Z | Question from Code | v1 | how do we make sure that when process only creates one child and control the total number of processes | for (int i = 0; i < iterations; i++) {
if (created == 0){
int created = fork();
if (created < 0) {
perror("fork");
exit(1);
} else if (created > 0) {
wait(&waitstatus);
}
}
printf("ppid = %d, pid = %d, i = %d\n", getppid(), getpid(), i);
}
| null | null |
63c647b05f004bf4898cf5d6 | 2023-02-27T22:52:24.060Z | Question from Code | v1 | why does the parent process fork 2 processes? | int main() {
int iterations = 2;
int created = 0;
int n = 0;
for (int i = 0; i < iterations; i++) {
if (created == 0){
int created = fork();
if (created < 0) {
perror("fork");
exit(1);
} else if(created > 0) {
wait(&n);
}
}
printf("ppid = %d, pid = %d, i = %d\n", getppid(), getpid(), i);
}
return 0;
}
| null | null |
63c647b05f004bf4898cf5d6 | 2023-02-27T22:57:10.932Z | Question from Code | v1 | why does the parent process fork 2 processes when created changes to a non 0 value | int main() {
int iterations = 2;
int created = 0;
int n = 0;
for (int i = 0; i < iterations; i++) {
if (created == 0){
int created = fork();
if (created < 0) {
perror("fork");
exit(1);
} else if(created > 0) {
wait(&n);
}
}
printf("ppid = %d, pid = %d, i = %d\n", getppid(), getpid(), i);
}
return 0;
}
| null | null |
63c647b05f004bf4898cf5d6 | 2023-03-07T00:07:57.878Z | Question from Code | v1 | this program uses a different file called validate, which validates the inputed password and username. The input (from standard input) is in this form: file_name \n username \n password. But when I run my program (which forks a child and pipes the input to the child), stdin looks like this: file_name \n username \n password \n \n. Why? | int fds[2];
if (pipe(fds) == -1) {
return -1;
}
int n = fork();
if (n == -1) {
return -1;
} else if (n == 0) {
// child process
dup2(fds[0], STDOUT_FILENO);
close(fds[1]); // closed unused end
execl("./validate", "validate", NULL);
} else {
// parent process
close(fds[0]);
write(fds[1], user_id, 10); // hardcoded MAXPASSWORD
write(fds[1], password, 10);
int status;
if(wait(&status) == -1) {
return -1;
} else if (WIFEXITED(status)) { // checks id process exits normally
int validation = WEXITSTATUS(status);
if (validation == 0) {
printf(SUCCESS);
} else if (validation == 1) {
// error
return -1;
} else if (validation == 2) {
printf(INVALID);
} else if (validation == 3) {
printf(NO_USER);
} else if (validation == 0) {
printf(SUCCESS);
}
}
close(fds[1]);
} | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-07T00:12:39.831Z | Question from Code | v1 | this program uses a different file called validate, which validates the inputed password and username. The input (from standard input) is in this form: file_name \n username \n password. But when I run my program (which forks a child and pipes the input to the child), stdin looks like this: file_name \n username \n password \n \n. Why?
| int fds[2];
pipe(fds) == -1;
int n = fork();
if (n == 0) {
// child process
dup2(fds[0], STDOUT_FILENO);
close(fds[1]); // closed unused end
execl("./validate", "validate", NULL);
} else {
// parent process
close(fds[0]);
write(fds[1], user_id, 10); // hardcoded MAXPASSWORD
write(fds[1], password, 10);
int status;
wait(&status);
if (WIFEXITED(status)) { // checks id process exits normally
int validation = WEXITSTATUS(status);
if (validation == 0) {
printf(SUCCESS);
}
}
close(fds[1]);
} | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-07T00:39:01.946Z | Question from Code | v1 | When the parent process exits, why does the shell print the prompt again, causing the shell to read from stdin?
| int fds[2];
pipe(fds) == -1;
int n = fork();
if (n == 0) {
// child process
dup2(fds[0], STDOUT_FILENO);
close(fds[1]); // closed unused end
execl("./validate", "validate", NULL);
} else {
// parent process
close(fds[0]);
write(fds[1], user_id, 10); // hardcoded MAXPASSWORD
write(fds[1], password, 10);
int status;
wait(&status);
if (WIFEXITED(status)) { // checks id process exits normally
int validation = WEXITSTATUS(status);
if (validation == 0) {
printf(SUCCESS);
}
}
close(fds[1]);
} | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-07T00:40:03.380Z | Question from Code | v1 | When the parent process exits, why does the shell print the prompt again, causing the shell to read from stdin?
| int fds[2];
if (pipe(fds) == -1) {
return -1;
}
int n = fork();
if (n == -1) {
return -1;
} else if (n == 0) {
// child process
close(fds[1]); // closed unused end
dup2(fds[0], STDOUT_FILENO);
execl("./validate", "validate", NULL);
close(fds[0]);
} else {
// parent process
close(fds[0]);
write(fds[1], user_id, 10); // hardcoded MAXPASSWORD
write(fds[1], password, 10);
close(fds[1]);
int status;
if(wait(&status) == -1) {
return -1;
} else if (WIFEXITED(status)) { // checks id process exits normally
int validation = WEXITSTATUS(status);
if (validation == 0) {
printf(SUCCESS);
}
}
}
return 0; | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-07T00:41:42.585Z | Question from Code | v1 | When the parent process exits, how do you keep shell from printing the prompt again, causing the shell to read from stdin?
| int fds[2];
if (pipe(fds) == -1) {
return -1;
}
int n = fork();
if (n == -1) {
return -1;
} else if (n == 0) {
// child process
close(fds[1]); // closed unused end
dup2(fds[0], STDOUT_FILENO);
execl("./validate", "validate", NULL);
close(fds[0]);
} else {
// parent process
close(fds[0]);
write(fds[1], user_id, 10); // hardcoded MAXPASSWORD
write(fds[1], password, 10);
close(fds[1]);
int status;
if(wait(&status) == -1) {
return -1;
} else if (WIFEXITED(status)) { // checks id process exits normally
int validation = WEXITSTATUS(status);
if (validation == 0) {
printf(SUCCESS);
}
}
}
return 0; | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-07T00:43:50.283Z | Question from Code | v1 | this program uses a different file called validate, which validates the inputed password and username. The input (from standard input) is in this form: file_name \n username \n password. But when I run my program (which forks a child and pipes the input to the child), stdin looks like this: file_name \n username \n password \n \n. Why does this happen, and how do I mitigate it?
| int fds[2];
if (pipe(fds) == -1) {
return -1;
}
int n = fork();
if (n == -1) {
return -1;
} else if (n == 0) {
// child process
close(fds[1]); // closed unused end
dup2(fds[0], STDOUT_FILENO);
execl("./validate", "validate", NULL);
close(fds[0]);
} else {
// parent process
close(fds[0]);
write(fds[1], user_id, 10); // hardcoded MAXPASSWORD
write(fds[1], password, 10);
close(fds[1]);
int status;
if(wait(&status) == -1) {
return -1;
} else if (WIFEXITED(status)) { // checks id process exits normally
int validation = WEXITSTATUS(status);
if (validation == 0) {
printf(SUCCESS);
}
}
}
return 0; | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-07T03:33:29.203Z | Question from Code | v1 | why is it the validate file asks for input from stdin in the form: <username> \n <password> \n but this code asks for input in the form: <username> \n <password> \n \n \n \n? How do I fix this? | #include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
// NOTE: MAX_PASSWORD must be less than MAXLINE/2
#define MAXLINE 32
#define MAX_PASSWORD 10
#define PASSWORD_FILE "pass.txt"
/* Reads two chunks from stdin, and checks if they match a user id
* and password pair from a password file. The first chunk (MAX_PASSWORD bytes)
* will contain a user id, and the second chunk (MAX_PASSWORD bytes) will
* contain a password.
*
* The program exits with a value of
* 0 if the user id and password match,
* 1 if there is an error,
* 2 if the user id is found but the password does not match, and
* 3 if the user id is not found in the password file.
*/
/* Note that read will read at most MAX_PASSWORD bytes. This means that the
* longest password we can support is MAX_PASSWORD. We can't count on the
* caller to send the null termination character, so we have to ensure
* that we terminate the string that is sent anyway.
*
* If the input is coming from the console/keyboard, then the write calls
* are managed by the shell which will process each piece of input
* separately.
* However, if the input is coming from a pipe, there is no guarantee that
* two writes generated by checkpasswd will send the data such that it
* will be read by the two reads below. The means that it is important for
* checkpasswd to send exactly as many bytes that validate is expecting.
* Otherwise the behaviour may be unpredicatable.
*
* This also means that checkpasswd should report an invalid password
* or no user_id if the user input is longer than MAX_PASSWORD.
*/
int main(void){
int n, user_length;
char userid[MAXLINE];
char password[MAXLINE];
if((n = read(STDIN_FILENO, userid, MAX_PASSWORD)) == -1) {
perror("read");
exit(1);
} else if(n == 0) {
fprintf(stderr, "Error: could not read from stdin");
exit(1);
}
// Make sure user id is null-terminated
if(n <= MAX_PASSWORD) {
userid[n] ='\0';
}
// Remove newline character if it exists
char *newline;
if((newline = strchr(userid, '\n')) != NULL) {
*newline = '\0';
}
if((n = read(STDIN_FILENO, password, MAX_PASSWORD)) == -1) {
perror("read");
exit(1);
} else if(n == 0) {
fprintf(stderr, "Error: could not read from stdin");
exit(1);
}
// Make sure password is null-terminated
if(n <= MAX_PASSWORD) {
password[n] ='\0';
}
// Remove newline character if it exists
if((newline = strchr(password, '\n')) != NULL) {
*newline = '\0';
}
// Prepare the userid:password string to compare to password file entries.
// We expect userid to have enough space to concatenate ":" + password
// but we will play it safe and use strncat
strncat(userid, ":", MAXLINE - strlen(userid) - 1);
user_length = strlen(userid);
strncat(userid, password, MAXLINE - strlen(userid) - 1);
FILE *fp = fopen(PASSWORD_FILE, "r");
if(!fp) {
perror("fopen");
exit(1);
}
char line[MAXLINE];
while(fgets(line, sizeof(line) - 1, fp)) {
line[strlen(line) - 1] = '\0';
if (strcmp(userid, line) == 0) {
fclose(fp);
exit(0); // found match
}
else if(strncmp(userid, line, user_length) == 0) {
fclose(fp);
exit (2); // invalid password
}
}
fclose(fp);
exit(3); // no such user
}
| null | null |
63c647b05f004bf4898cf5d6 | 2023-03-07T03:36:23.083Z | Question from Code | v1 | why is it the validate file asks for input from stdin in the form: <username> \n <password> \n but this code asks for input in the form: <username> \n <password> \n \n \n \n? How do I fix this?
| #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);
}
// TODO
// checking length
if (strlen(user_id) > 10) {
printf(NO_USER);
exit(1);
}
if (strlen(password) > 10) {
printf(INVALID);
exit(1);
}
// the hard shit
int fds[2];
if (pipe(fds) == -1) {
exit(1);
}
int n = fork();
if (n < 0) {
exit(1);
} else if (n == 0) {
// child process
dup2(fds[0], STDOUT_FILENO);
close(fds[0]);
close(fds[1]);
execl("./validate", "validate", NULL);
exit(1);
} else {
// parent process
close(fds[0]);
write(fds[1], user_id, 10); // hardcoded MAXPASSWORD
write(fds[1], password, 10);
close(fds[1]);
int status;
if(wait(&status) == -1){
exit(1);
}
if (WIFEXITED(status)) { // checks id process exits normally
int validation = WEXITSTATUS(status);
if (validation == 0) {
printf("%s", SUCCESS);
} else if (validation == 1) {
// error
exit(1);
} else if (validation == 2) {
printf("%s", INVALID);
} else if (validation == 3) {
printf("%s", NO_USER);
}
} else {
exit(1);
}
}
return 0;
} | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-07T03:40:05.260Z | 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);
}
// TODO
// checking length
if (strlen(user_id) > 10) {
printf(NO_USER);
exit(1);
}
if (strlen(password) > 10) {
printf(INVALID);
exit(1);
}
// the hard shit
int fds[2];
if (pipe(fds) == -1) {
exit(1);
}
int n = fork();
if (n < 0) {
exit(1);
} else if (n == 0) {
// child process
dup2(fds[0], STDOUT_FILENO);
close(fds[0]);
close(fds[1]);
execl("./validate", "validate", NULL);
exit(1);
} else {
// parent process
close(fds[0]);
write(fds[1], user_id, 10); // hardcoded MAXPASSWORD
write(fds[1], password, 10);
close(fds[1]);
int status;
if(wait(&status) == -1){
exit(1);
}
if (WIFEXITED(status)) { // checks id process exits normally
int validation = WEXITSTATUS(status);
if (validation == 0) {
printf("%s", SUCCESS);
} else if (validation == 1) {
// error
exit(1);
} else if (validation == 2) {
printf("%s", INVALID);
} else if (validation == 3) {
printf("%s", NO_USER);
}
} else {
exit(1);
}
}
return 0;
} | why is it the validate file asks for input from stdin in the form: <username> \n <password> \n but this code asks for input in the form: <username> \n <password> \n \n \n \n, which causes the program to take in the last 2 lines (which are blank) as inputs. How do I fix this? | null |
63c647b05f004bf4898cf5d6 | 2023-03-07T03:41:22.290Z | 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.
*/
if (strlen(user_id) > 10) {
printf(NO_USER);
exit(1);
}
if (strlen(password) > 10) {
printf(INVALID);
exit(1);
}
int fds[2];
if (pipe(fds) == -1) {
exit(1);
}
int n = fork();
if (n < 0) {
exit(1);
} else if (n == 0) {
// child process
dup2(fds[0], STDOUT_FILENO);
close(fds[0]);
close(fds[1]);
execl("./validate", "validate", NULL);
exit(1);
} else {
// parent process
close(fds[0]);
write(fds[1], user_id, 10); // hardcoded MAXPASSWORD
write(fds[1], password, 10);
close(fds[1]);
int status;
if(wait(&status) == -1){
exit(1);
}
if (WIFEXITED(status)) { // checks id process exits normally
int validation = WEXITSTATUS(status);
if (validation == 0) {
printf("%s", SUCCESS);
} else if (validation == 1) {
// error
exit(1);
} else if (validation == 2) {
printf("%s", INVALID);
} else if (validation == 3) {
printf("%s", NO_USER);
}
} else {
exit(1);
}
}
return 0;
} | why is it the validate file asks for input from stdin in the form: <username> \n <password> \n but this code asks for input in the form: <username> \n <password> \n \n \n \n, which causes the program to take in the last 2 lines (which are blank) as inputs. How do I fix this? | null |
63c647b05f004bf4898cf5d6 | 2023-03-09T19:11:11.358Z | Question from Code | v2 | what would this print
| int main() {
char *str;
strncat(str, "hello", 3);
printf("%s\n", str);
return 0;
} | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-09T19:12:26.773Z | Question from Code | v2 | what would this print | int main() {
char *str;
strncpy(str, "hello", 3);
printf("%s\n", str);
return 0;
} | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-09T19:35:51.956Z | General Question | v2 | how to use strtok()
| null | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-10T00:14:17.612Z | Question from Code | v2 | is the tab ('\t') included in the first token? If so, how do I get rid of it?
| int main () {
char str[100] = "\tgcc -Wall -g -std=gnu99 -c shit.c";
const char s[2] = " ";
char *token;
/* get the first token */
token = strtok(str, s);
/* walk through other tokens */
while(token != NULL ) {
printf( "\n%s", token );
token = strtok(NULL, s);
}
return(0);
} | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-10T00:17:13.711Z | General Question | v2 | if you tokenize a str, what is strlen(token)? | null | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-10T00:21:31.867Z | Help Write Code | v2 | null | null | null | how to get number of tokens from strtok |
63c647b05f004bf4898cf5d6 | 2023-03-10T00:29:30.833Z | Question from Code | v2 | does this give me the str removing '\t'? | strchr(tokens, '\t') + 1; | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-10T01:18:52.676Z | General Question | v2 | if you have array = char[][], what does strlen(array) give you | null | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-10T01:19:39.492Z | Question from Code | v2 | If you have double array = char[x][y], how do you find the x number? | strchr(tokens, '\t') + 1; | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-10T01:20:06.333Z | General Question | v2 | If you have double array = char[x][y], how do you find the x number? | null | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-10T01:23:46.128Z | Help Write Code | v2 | null | null | null | c how to print 2d array when you dont know the dimensions |
63c647b05f004bf4898cf5d6 | 2023-03-10T01:28:26.739Z | Help Write Code | v2 | null | null | null | how do I while loop through a 2d char array to print each word in the array
|
63c647b05f004bf4898cf5d6 | 2023-03-10T01:42:15.102Z | Help Write Code | v2 | null | null | null | how do I assign space for 2d array using malloc |
63c647b05f004bf4898cf5d6 | 2023-03-10T01:43:36.468Z | Question from Code | v2 | why does the *char give error | char **args = malloc(sizeof(*char) * len); | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-10T01:53:17.449Z | Question from Code | v2 | why does this give error and how do I fix it? | fread(line, MAXLINE, sizeof(char), fp);
while (line != EOF) { | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-10T03:50:19.156Z | Question from Code | v2 | why does this line of code give error
| char *tokens = strtok(rest_of_line, ' '); | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-10T04:08:32.288Z | Question from Code | v2 | why does this give error | char *line;
fgets(line, MAXLINE, fp); | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-10T04:33:49.233Z | General Question | v2 | how to run gdb for a file that doesn't have a main function? And how do I use gdb with input files (the code I want to debug needs an input file)? | null | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-10T04:39:16.872Z | General Question | v2 | wen I use gdb: "gdb pmake.c < handout_example/handout.mk" I get there error: "not in executable format: file format not recognized". | null | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-10T04:41:23.948Z | General Question | v2 | when I use gdb: "gdb pmake < handout_example/handout.mk" I get there error: "not in executable format: file format not recognized". | null | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-10T04:41:52.639Z | General Question | v2 | when I use gdb: "gdb pmake < handout_example/handout.mk" I get there error: "not in executable format: file format not recognized". pmake has already been compiled by gcc | null | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-10T04:42:15.622Z | General Question | v2 | when I use gdb: "gdb pmake < handout_example/handout.mk" I get there error: "not in executable format: file format not recognized". pmake has already been compiled by gcc -g | null | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-11T01:25:41.063Z | Question from Code | v2 | should strncpy's last argument be strlen(token) or strlen(token) + 1 if strlen(token) = number of letters I want to copy (not include null terminator) | char **args = mallo(sizeof(char *) * len);
for (int i = 0; i < len; i++) {
args[i] = malloc(sizeof(char) * strlen(token) + 1);
strncpy(args[i], token, strlen(token));
} | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-11T01:39:13.392Z | General Question | v2 | how do I check if 2 chars are equal (I want to check if the first char in a string is a tab) | null | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-11T01:54:31.075Z | Question from Code | v2 | Assume all function calls from nonstandard c libraries are helpers that work perfectly. This program is meant to create Node structures to organize make files.
There's a function that prints the structure in a format to mimic a make file on standard output.
But when I call on the corresponding print function in my terminal, it just keeps asking for input and I can't exit out (I have to kill terminal). What am I doing wrong? | Rule *parse_file(FILE *fp) {
Rule *target_cur;
Rule *target_head = NULL;
Rule *other_head = NULL;
char line[MAXLINE];
fgets(line, MAXLINE, fp);
while (line != NULL) {
if (is_comment_or_empty(line) == 1) {
// line is empty or is a comment
} else if (strchr(line, ':') != NULL) {
// line contains start of rule (target & prerequisites)
// target:
target_cur = check_target(target_head, other_head, line);
// dependencies
check_dependencies(target_cur, target_head, other_head, strchr(line, ':') + 1);
// curr is still pointed to the same rule (as it should)
} else if (strncmp(line, "\t", sizeof(char)) == 0) {
// line starts with tab, AKA contains actions (should mitigate the \r\n issues, I had 'else' before)
char *tokens = strtok(line, " ");
int len = 0;
while (tokens != NULL) {
len++;
strtok(NULL, " ");
}
check_actions(target_cur, line, len - 1); // len - 1 cause of the tab = first token
}
}
return target_head;
} | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-11T03:26:37.243Z | Question from Code | v2 | why does this code cause a segmentation fault? |
void check_dependencies(Rule *curr, Rule *target_head, Rule *other_head, char *line) {
// line passed in starts at space right after ':'
char *token = strtok(line, " ");
while (token != NULL) {
Dependency *new = malloc(sizeof(Dependency));
Dependency *curr_dep;
if (target_contains(target_head, token) != NULL) {
new->rule = target_contains(target_head, token);
} else if (other_contains(other_head, token) != NULL) {
new->rule = other_contains(other_head, token);
} else {
// this target doesn't exist yet, create an 'other' Rule and attach to end of other lst
Rule *new_rule = malloc(sizeof(Rule));
Rule *curr_other = other_head;
new_rule->actions = NULL;
new_rule->dependencies = NULL;
new_rule->next_rule = NULL;
new_rule->target = malloc(sizeof(char) * (strlen(token) + 1));
strncpy(new_rule->target, token, strlen(token) + 1);
// attach to end of 'other' list
while (curr_other->next_rule != NULL) {
curr_other = curr_other->next_rule;
}
curr_other->next_rule = new_rule;
}
if (curr->dependencies == NULL) {
curr->dependencies = new;
curr_dep = new;
} else {
curr_dep->next_dep = new;
curr_dep = new;
}
token = strtok(NULL, " ");
}
} | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-11T03:37:54.478Z | Question from Code | v2 | Assuming curr cannot be NULL, why does this code cause a segmentation fault? |
void check_dependencies(Rule *curr, Rule *target_head, Rule *other_head, char *line) {
// line passed in starts at space right after ':'
char *token = strtok(line, " ");
while (token != NULL) {
Dependency *new = malloc(sizeof(Dependency));
Dependency *curr_dep;
if (target_contains(target_head, token) != NULL) {
new->rule = target_contains(target_head, token);
} else if (other_contains(other_head, token) != NULL) {
new->rule = other_contains(other_head, token);
} else {
// this target doesn't exist yet, create an 'other' Rule and attach to end of other lst
Rule *new_rule = malloc(sizeof(Rule));
Rule *curr_other = other_head;
new_rule->actions = NULL;
new_rule->dependencies = NULL;
new_rule->next_rule = NULL;
new_rule->target = malloc(sizeof(char) * (strlen(token) + 1));
strncpy(new_rule->target, token, strlen(token) + 1);
// attach to end of 'other' list
while (curr_other->next_rule != NULL) {
curr_other = curr_other->next_rule;
}
curr_other->next_rule = new_rule;
}
if (curr->dependencies == NULL) {
curr->dependencies = new;
curr_dep = new;
} else {
curr_dep->next_dep = new;
curr_dep = new;
}
token = strtok(NULL, " ");
}
} | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-11T03:47:39.425Z | Question from Code | v2 | Assuming curr cannot be NULL, why does this code cause a segmentation fault? |
void check_dependencies(Rule *curr, Rule *target_head, Rule *other_head, char *line) {
// line passed in starts at space right after ':'
char *token = strtok(line, " ");
while (token != NULL) {
Dependency *new = malloc(sizeof(Dependency));
Dependency *curr_dep;
if (target_contains(target_head, token) != NULL) {
new->rule = target_contains(target_head, token);
} else if (other_contains(other_head, token) != NULL) {
new->rule = other_contains(other_head, token);
} else {
// this target doesn't exist yet, create an 'other' Rule and attach to end of other lst
Rule *new_rule = malloc(sizeof(Rule));
Rule *curr_other = other_head;
new_rule->actions = NULL;
new_rule->dependencies = NULL;
new_rule->next_rule = NULL;
new_rule->target = malloc(sizeof(char) * (strlen(token) + 1));
strncpy(new_rule->target, token, strlen(token) + 1);
if (curr_other == NULL) {
other_head = new_rule;
} else {
while (curr_other->next_rule != NULL) {
curr_other = curr_other->next_rule;
}
curr_other->next_rule = new_rule;
}
}
if (curr->dependencies == NULL) {
curr->dependencies = new;
curr_dep = new;
} else {
curr_dep->next_dep = new;
curr_dep = new;
}
token = strtok(NULL, " ");
}
} | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-11T03:56:20.780Z | General Question | v2 | when I call strtok twice in a row on the same line, it gives me segmentation fault the second time around. How to I mitigate this so I can call strtok again? | null | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-11T04:10:33.746Z | Question from Code | v2 | the first print statement prints but the following print statements don't instead, the terminal screen goes blank. What causes this error? | if (strncmp(line, "\t", sizeof(char)) == 0) {
printf("enter into action line \n");
// line starts with tab, AKA contains actions (should mitigate the \r\n issues, I had 'else' before)
char *copy = strdup(line);
char *tokens = strtok(copy, " ");
int len = 0;
while (tokens != NULL) {
printf("token: %s\n", tokens);
len++;
strtok(NULL, " ");
}
printf("number of arguments: %d \n", len);
check_actions(target_cur, line, len - 1); // len - 1 cause of the tab = first token
printf("first argument: %s \n", target_cur->actions->args[0]);
} | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-11T04:12:15.018Z | General Question | v2 | what function can I use to count the number of tokens there are after calling strtok | null | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-11T04:13:25.396Z | General Question | v2 | is there a function that returns the number occurences of a char within a string? | null | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-11T04:20:28.490Z | Question from Code | v2 | Assuming curr cannot be null, what might be causing a segmentation error? |
void check_actions(Rule *curr, char *line, int len) {
Action *new_action = malloc(sizeof(Action));
new_action->next_act = NULL;
Action *cur_action = NULL;
if (curr->dependencies == NULL) {
curr->actions = new_action;
cur_action = new_action;
} else {
cur_action->next_act = new_action;
cur_action = new_action;
}
char *copy = strdup(line);
char *token = strtok(copy, " ");
char **a = malloc(sizeof(char *) * len);
int i = 0;
while (token != NULL) {
if (strcmp(token, "\t") != 0) {
// AKA not a tab, update args
a[i] = malloc(sizeof(char) * (strlen(token) + 1));
strncpy(a[i], token, strlen(token) + 1);
}
i++;
strtok(NULL, " ");
}
cur_action->args = a;
} | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-11T04:24:38.691Z | Question from Code | v2 | Assuming curr cannot be null, what might be causing a segmentation error? |
void check_actions(Rule *curr, char *line, int len) {
Action *new_action = malloc(sizeof(Action));
new_action->next_act = NULL;
Action *cur_action = NULL;
if (curr->actions == NULL) {
curr->actions = new_action;
cur_action = new_action;
} else {
cur_action->next_act = new_action;
cur_action = new_action;
}
char *copy = strdup(line);
char *token = strtok(copy, " ");
char **a = malloc(sizeof(char *) * len);
int i = 0;
while (token != NULL) {
if (strcmp(token, "\t") != 0) {
// AKA not a tab, update args
a[i] = malloc(sizeof(char) * (strlen(token) + 1));
strncpy(a[i], token, strlen(token) + 1);
}
i++;
token = strtok(NULL, " ");
}
cur_action->args = a;
} | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-11T04:37:27.649Z | General Question | v2 | I run a file with terminal command: ./pmake -f handout.mk -o, where -f and -o are defined in pmake.c, handout.mk is a file in the same folder, and pmake is compiled from pmake.c
How do I run gdb to test this exact input? | null | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-11T04:51:57.749Z | General Question | v2 | im running gdb and when I write display <variable> where variable is a string from a file, gdb displays it in binary. Is there a way to have gdb display the variable in human readable text?
| null | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-11T05:06:46.532Z | General Question | v2 | in gdb, how do I go back a line? | null | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-11T05:44:22.585Z | Question from Code | v2 | I'm trying to remove the rest of the string line starting from '\r', but this gives me warnings when I compile. Why, and how do I fix this? | char *ptr = strchr(line, '\r');
ptr = '\0'; | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-11T05:47:20.198Z | Question from Code | v2 | when I run the code this is the warning that pops up in gcc
warning: null argument where non-null required (argument 2) [-Wnonnull]
206 | strcpy(ptr, '\0');
what does it mean and how do i fix this? | char *ptr = strchr(line, '\r');
strcpy(ptr, '\0'); | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-11T06:13:04.654Z | Question from Code | v2 | why doesn't this code print "outside 7" to standard 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 |
63c647b05f004bf4898cf5d6 | 2023-03-11T15:33:17.753Z | General Question | v2 | how do I remove whitespace from a string
| null | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-11T15:33:55.273Z | General Question | v2 | how do I remove whitespace from a string without strtok | null | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-12T05:24:59.290Z | General Question | v2 | how to use struct stat to compare the last modified times of two files
| null | null | null |
63c647b05f004bf4898cf5d6 | 2023-03-12T20:45:39.270Z | Question from Code | v2 | line 3 gives "warning: passing argument 1 of ‘stat’ from incompatible pointer type [-Wincompatible-pointer-types]" error when I compile it on gcc. What causes this problem and how do I fix it? | Dependency *dep_cur = rule->dependencies;
struct stat check_stat;
stat(dep_cur, &check_stat); | null | null |
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