Read string of any length in C https://codereview.stackexchange.com/questions/228979/read-string-of-any-length-in-c

read_string.c

/* Improved version for https://codereview.stackexchange.com/questions/228979/read-string-of-any-length-in-c */

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

/* Reads string input up to, but not including, the first newline or EOF.
 * Returns a pointer to the string, or NULL on error.
 * The pointer to the string must be freed.
 */
char* input() {
    size_t bufsize = 10;  /* Initial buffer size. */
    char *s = malloc(bufsize);
    if (s == NULL) {
        return NULL;
    }
    size_t s_len = 0;  /* Current length of string excluding null character. */
    int ch;
    while((ch = getchar()) != '\n' && ch != EOF) {
        s[s_len] = (char) ch;
        s_len++;
        if (s_len + 1 > bufsize) {
            bufsize *= 2;
            char *temp_buf = realloc(s, bufsize);
            if (temp_buf == NULL) {
                free(s);
                return NULL;
            }
            s = temp_buf;
        }
    }
    s[s_len] = '\0';
    return s;
}

int main() {
    printf("Name: ");
    fflush(stdout);
    char *s = input();
    if (s == NULL) {
        fprintf(stderr, "Error: input()\n");
        exit(1);
    }
    printf("%s\n", s);
    free(s);
    return 0;
}