Input Characters And Strings in C Programming Language

Reading characters and strings from the user is an essential part of many C programs. This tutorial will show you how to use the standard C library functions getchar, scanf, and fgets to read characters and strings as input.

Reading single characters using getchar

The getchar function reads a single character from the standard input (usually the keyboard) and returns its integer representation. You can store this integer in a variable of type int and then cast it to a char to get the actual character.

Example:

#include <stdio.h>

int main() {
    printf("Enter a character: ");
    int input = getchar();
    char character = (char)input;

    printf("You entered: '%c'\n", character);
    return 0;
}

Reading strings using scanf

The scanf function is a versatile function that can read various data types from standard input. To read a string, you can use the %s format specifier. However, scanf stops reading input when it encounters whitespace, which means it cannot be used to read strings with spaces.

Example:

#include <stdio.h>

int main() {
    char name[20];
    
    printf("Enter your name: ");
    scanf("%s", name);

    printf("Hello, %s!\n", name);
    return 0;
}

Reading strings using fgets

The fgets function can read a string, including spaces, from a given file stream. To read a string from standard input, you can use fgets with the stdin file stream. The fgets function reads a specified number of characters or until it encounters a newline character or end-of-file (whichever comes first). It also includes the newline character in the resulting string, which you may need to remove.

Example:

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

int main() {
    char sentence[50];

    printf("Enter a sentence: ");
    fgets(sentence, sizeof(sentence), stdin);

    // Remove the newline character, if present
    size_t len = strlen(sentence);
    if (sentence[len - 1] == '\n') {
        sentence[len - 1] = '\0';
    }

    printf("You entered: \"%s\"\n", sentence);
    return 0;
}

In summary, you can use the getchar function to read single characters and the scanf or fgets functions to read strings in C programming. While scanf is convenient for reading simple strings without spaces, fgets provides a more robust way to read strings that include spaces and manage buffer sizes.

Reading Characters from stdin in C:

#include <stdio.h>

int main() {
    char ch;

    printf("Enter a character: ");
    scanf("%c", &ch);

    printf("You entered: %c\n", ch);

    return 0;
}

Input Functions for Characters in C Language:

The getchar() function can be used to read a single character from stdin.

#include <stdio.h>

int main() {
    char ch;

    printf("Enter a character: ");
    ch = getchar();

    printf("You entered: %c\n", ch);

    return 0;
}

C Program Examples with Character Input:

#include <stdio.h>

int main() {
    char ch1, ch2;

    printf("Enter two characters separated by space: ");
    scanf("%c %c", &ch1, &ch2);

    printf("You entered: %c and %c\n", ch1, ch2);

    return 0;
}

String Input in C Programming:

#include <stdio.h>

int main() {
    char name[50];

    printf("Enter your name: ");
    fgets(name, sizeof(name), stdin);

    printf("Hello, %s", name);

    return 0;
}

Using scanf for Character and String Input in C:

#include <stdio.h>

int main() {
    char ch;
    char name[50];

    printf("Enter a character: ");
    scanf(" %c", &ch);  // Note the space before %c to consume any whitespace

    printf("Enter your name: ");
    scanf("%s", name);

    printf("You entered: %c and %s\n", ch, name);

    return 0;
}

Safe String Input Techniques in C:

Using fgets for string input to avoid buffer overflow.

#include <stdio.h>

int main() {
    char name[50];

    printf("Enter your name: ");
    fgets(name, sizeof(name), stdin);

    printf("Hello, %s", name);

    return 0;
}

Handling Whitespace in Character and String Input in C:

Using scanf with %c to handle whitespace in character input.

#include <stdio.h>

int main() {
    char ch;

    printf("Enter a character: ");
    scanf(" %c", &ch);  // Note the space before %c to consume any whitespace

    printf("You entered: %c\n", ch);

    return 0;
}

Character and String Input Validation in C:

#include <stdio.h>

int main() {
    char gender;

    printf("Enter your gender (M/F): ");
    scanf(" %c", &gender);

    if (gender == 'M' || gender == 'F') {
        printf("Valid gender: %c\n", gender);
    } else {
        printf("Invalid gender\n");
    }

    return 0;
}