Why does my fgets method turn out to be like this? - c

Question

I cannot input my "details" because it doesn't leave any space for me to.
int addTask(NODE **head){
//IGNORE NODES
NODE *p, *temp, *ptr, *a;
DATE d;
p = *head;
a = *head;
char x[32];
char y[32];
char name[32];
char details[128];
int month;
int day;
int year;
int priority;
int intDate;
int i;
printf("\n");
printf("Enter task name: ");
scanf("%s", name);
printf("Enter task details:");
fgets(details, 128, stdin); //PROBLEM LIES HERE
printf("[mm dd yyyy] Enter task deadline: ");
scanf("%d %d %d", &month, &day, &year);
printf("Enter priority: ");
scanf("%d", &priority);
/*code conditions here*/
}
In my terminal it turns out like this:
User#Lynn /cygdrive/c/users/user/academic/c
$ gcc -o a Yago_exer11.c
User#Lynn /cygdrive/c/users/user/academic/c
$ ./a
1. Add a task
2. Remove a task
3. Search for a task
4. View all tasks
5. View tasks by priority
6. Exit
Choice: 1
Enter task name: hello
Enter task details:[mm dd yyyy] Enter task deadline: 09 09 09 //PROBLEM
Enter priority: 1
Adding...
I tried using scanf(%^[\n]) as an alternative but it turns out to have the same output. Can someone tell me what's wrong with my code?

Answer 1

Try to put getchar(); after scanf("%s", name);

Answer 2

The functions fgets and scanf work differently. It's best not to mix them.
scanf scans the input. It doesn't know about lines; it treats all new-line characters, tabs and spaces simply as "white space". It also stops after conversions, so that after reading, the next file reading operations starts directly after that input, which is usually just before a new line. (There's also the pitfall of trying to parse decimal numbers over and over when the input gets stuck in something that is not a number.)
fgets reads lines from the input. That method goes more naturally with your prompt-and-input strategy: The program asks a question, the user answers and presses enter.
I suggest a two-step approach. Read lines first, then analyse these lines and extract the data. Depending on what the data looks like, you can tokenise the line with strtok for example and convert the tokens or you can use sscanf, scanf's sister function for scanning strings, to scan the data.
Here's a version of your example that shows several strategies of parsing input with that two-step spproach:
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
int main(void)
{
char line[128];
char name[32];
char details[128];
int month;
int day;
int year;
int priority;
int n;
// read lines until one of them contains a word
printf("Enter task name: ");
do {
if (fgets(line, sizeof(line), stdin) == 0) return 1;
n = sscanf(line, "%s", name);
} while (n != 1);
// details may be empty, so read them directly
printf("Enter task details: ");
if (fgets(details, sizeof(details), stdin) == 0) return 1;
strtok(details, "\n");
// prompt and read lines until one of them has a valid date
do {
printf("[mm dd yyyy] Enter task deadline: ");
if (fgets(line, sizeof(line), stdin) == 0) return 1;
n = sscanf(line, "%d %d %d", &month, &day, &year);
if (n == 3) {
if (month < 1 || month > 12) n = 0;
if (day < 1 || day > 31) n = 0;
}
if (n != 3) printf("Invalid date\n");
} while (n != 3);
// read priority until a number (any number) is given
printf("Enter priority: ");
do {
if (fgets(line, sizeof(line), stdin) == 0) return 1;
n = sscanf(line, "%d", &priority);
} while (n != 1);
// echo results
printf("name: %s\n", name);
printf("details: %s\n", details);
printf("data: %02d/%02d/%04d\n", month, day, year);
printf("prio: %d\n", priority);
return 0;
}
The example is far from perfect. For example, what should happen when the user presses Ctrl-Z or Ctrl-D to end the input stream? The standard input isn't particularly suited for manual input.