Reading Whole Lines with fgets

scanf("%s") stops at a space. To read a whole line, use fgets:

#include <stdio.h>

int main() {
    char line[100];
    fgets(line, 100, stdin);
    printf("You typed: %s", line);
    return 0;
}

Input (what the user types)

I love learning C

Output

You typed: I love learning C

• line is where the text goes.
• 100 is the size of the array, so fgets never writes too much. That makes it safe.
• stdin means "read from the keyboard" (standard input).

Removing the newline

fgets keeps the Enter key ('\n') at the end of the line. That's why we didn't need \n in the printf above. Usually you want to remove it. strcspn(line, "\n") finds where the '\n' is, and we put '\0' there:

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

int main() {
    char name[50];
    fgets(name, 50, stdin);
    name[strcspn(name, "\n")] = '\0';
    printf("[%s] has %d characters\n", name, (int) strlen(name));
    return 0;
}

Input (what the user types)

Ada Lovelace

Output

[Ada Lovelace] has 12 characters

Tip: Copy that line – name[strcspn(name, "\n")] = '\0'; – every time you use fgets.

Text to number

atoi (from <stdlib.h>) turns text like "42" into the number 42. atof does the same for decimals:

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

int main() {
    char a[10] = "42";
    char b[10] = "2.5";
    int n = atoi(a);
    double d = atof(b);
    printf("%d %.1f\n", n + 1, d * 2);
    return 0;
}

Output

43 5.0

Number to text

sprintf works like printf, but writes into a string instead of the screen:

#include <stdio.h>

int main() {
    char label[30];
    int level = 7;
    sprintf(label, "Level-%03d", level);
    printf("%s\n", label);
    return 0;
}

Output

Level-007

Remember: fgets reads a whole line safely. Remove its '\n' with strcspn.