如何在 c 中使用 fgets 而不是 sscanf？

Question

i'm very new in c (and then i can't understand internet answers so well) and i'm triyng to use fgets, since i notices that sscanf picks only the first word of a string. so, i have a code like that. if my input is (for example): char line[100] = "My favourite animal is cat"; . i wrote this code with sscanf.

char fav_animal[10];

sscanf(line,"My favourite animal is %s",fav_animal);

And it works well with one word, but i want to use fgets because in my program an user can insert multiple words. So, i wanted to know what is the equivalent, written with the fgets, of the code written up.

Answer 1

The function fgets is useful for reading one line of user input as a string. However, if you already have a string and want to parse that, then fgets is useless.

If you have a string

char line[100] = "My favourite animal is cat";

and want to copy everything after "My favorite animal is" to another string fav_animal , then you can use the following code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main( void )
{
    char line[] = "My favourite animal is cat";

    char fav_animal[10];
    char start[] = "My favourite animal is ";
    size_t start_len = strlen( start );

    //make sure that line starts with "My favourite animal is "
    if ( strncmp( line, start, start_len ) != 0 )
    {
        printf( "Error, line does not start with expected string.\n" );
        exit( EXIT_FAILURE );
    }

    //copy remainder of line into fav_animal
    snprintf( fav_animal, sizeof fav_animal, "%s", line + start_len );

    //print fav_animal
    printf( "The content of fav_animal is: %s\n", fav_animal );
}

This program has the following output:

The content of fav_animal is: cat

This will also work if the animal's name consists of several words. For example, if I change

char line[] = "My favourite animal is cat";

to

char line[] = "My favourite animal is pit bull";

then the program will have the following output:

The content of fav_animal is: pit bull