Reading Strings

Big idea

scanf("%s") reads one word. fgets reads a whole line, spaces included — and never more than fits.

One word: scanf

char name[20];
scanf("%19s", name);

• No & — name is an array, so it's already an address.
• %19s — read at most 19 characters, leaving room for '\0' in a 20-char array.
• %s stops at the first space. Typing Maya Rao stores only Maya.

#include <stdio.h>

int main(void) {
    char first[20];
    scanf("%19s", first);
    printf("Hello, %s!\n", first);
    return 0;
}

input
Maya Rao

output
Hello, Maya!

A whole line: fgets

char line[50];
fgets(line, sizeof line, stdin);

• line — where to store it.
• sizeof line — the most it may store (50, including '\0') — fgets never overflows.
• stdin — read from the keyboard ("standard input").

One catch: fgets keeps the Enter key — a '\n' — at the end of what it read. Remove it before printing or comparing:

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

int main(void) {
    char line[50];
    fgets(line, sizeof line, stdin);
    line[strcspn(line, "\n")] = '\0';
    printf("[%s]\n", line);
    return 0;
}

input
Maya Rao from Chennai

output
[Maya Rao from Chennai]

strcspn(line, "\n") gives the index of the first '\n' (or the end, if there isn't one), and writing '\0' there cuts it off.

Watch it

Mixing scanf and fgets

After scanf("%d", &age), the Enter you pressed is still waiting. A following fgets reads that leftover '\n' straight away and returns an empty line:

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

int main(void) {
    int age;
    char city[40];
    scanf("%d", &age);
    fgets(city, sizeof city, stdin);
    city[strcspn(city, "\n")] = '\0';
    printf("%d, %s\n", age, city);
    return 0;
}

input
21
New Delhi

output
21, New Delhi

One fix: after the scanf, skip the rest of that line with while (getchar() != '\n'); before calling fgets.

Never use gets

Old code uses gets(line). It has no size limit, so long input overwrites memory — it was so dangerous that it was removed from the C language. Use fgets.

Think of it like

scanf("%s") is a listener who stops at the first pause. fgets listens until you finish the sentence — and has a notepad of a fixed size, so it never writes off the edge.

🕷️ Spidey-sense: When J. Jonah Jameson calls, scanf hears "PARKER!" and hangs up. fgets gets the whole rant — up to the size of my voicemail box.

Key terms

• fgets — Reads a line (with a size limit) into a char array.
• stdin — Standard input: normally the keyboard.
• Buffer overflow — Writing past the end of an array; %19s and fgets prevent it.