How to read & output an input with spaces and newlines

Question

I am attempting to scanf a multiline input in C and output it. However, I'm having trouble handling spaces and newline characters. If the input is:

Hello.
My name is John.
Pleased to meet you!

I want to output all three lines. But my output ends up being just:

Hello.

Here's my code:

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

int main() 
{
    char s[100];
    scanf("%[^\n]%*c", &s);
    printf(s);
    return 0;
}

Answer 1

Its much easier to use fgets() :

#include <stdio.h>

int main(void)
{
    char buffer[1000];
    while (fgets(buffer, sizeof(buffer), stdin) && buffer[0] != '\n') {
        printf("%s", buffer);
    }
}

An empty line (first character is newline) ends input.

---

If you have to read all input first before printing the result, things get a little bit more complicated:

#include <stddef.h>  // size_t
#include <stdlib.h>  // EXIT_FAILURE, realloc(), free()
#include <stdio.h>   // fgets(), puts()
#include <string.h>  // strlen(), strcpy()

int main(void)
{
    char buffer[1000];
    char *text = NULL;  // pointer to memory that will contain the whole text
    size_t total_length = 0;  // keep track of where to copy our buffer to

    while (fgets(buffer, sizeof(buffer), stdin) && buffer[0] != '\n') {
        size_t length = strlen(buffer);  // remember so we don't have to call
                                         // strlen() twice.
        // (re)allocate memory to copy the buffer to:
        char *new_text = realloc(text, total_length + length + 1); // + 1 for the
        if (!new_text) {  // if (re)allocation failed              terminating '\0'
            free(text);   // clean up our mess
            fputs("Not enough memory :(\n\n", stderr);                   
            return EXIT_FAILURE;
        }
        text = new_text;  // now its safe to discard the old pointer
        strcpy(text + total_length, buffer);  // strcpy instead of strcat so we don't
        total_length += length;               // have to care about uninitialized memory 
    }                                         // on the first pass *)

    puts(text);  // print all of it
    free(text);  // never forget
}

*) and it is also more efficient since strcat() would have to find the end of text before appending the new string. Information we already have.