C ctype.h ispunct() Function

ispunct() Function

The ispunct() function in C is used to determine if a character is a punctuation character. It checks whether a character falls within the set of graphical characters that are not alphanumeric. This function is particularly useful for parsing text and filtering out punctuation marks in data processing tasks.

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Syntax of ispunct()

int ispunct(int c);

Parameters

Parameter	Description
c	An integer representing the character to be checked, typically cast from a char or EOF.

In the default “C” locale, ispunct() considers all graphic characters that are not alphanumeric as punctuation. Note that other locales might define a different set of characters as punctuation, but the common property is that they are graphical and not letters or digits.

Return Value

The function returns a nonzero value (true) if the character is a punctuation character, and zero (false) otherwise.

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Examples for ispunct()

Example 1: Basic Check for a Punctuation Character

This example demonstrates how to use ispunct() to check a single character for punctuation.

Program

#include <stdio.h>
#include <ctype.h>

int main() {
    int ch = '!';
    
    if (ispunct(ch)) {
        printf("The character %c is a punctuation character.\n", ch);
    } else {
        printf("The character %c is not a punctuation character.\n", ch);
    }
    
    return 0;
}

Explanation:

1. A character is assigned the value '!'.
2. The ispunct() function checks if '!' is a punctuation character.
3. Since '!' is considered punctuation, the program prints a confirmation message.

Program Output:

The character ! is a punctuation character.

Example 2: Checking Multiple Characters for Punctuation

This example iterates through a string and uses ispunct() to identify punctuation characters among a mix of characters.

Program

#include <stdio.h>
#include <ctype.h>

int main() {
    char testStr[] = "Hello, World!";
    int i = 0;
    
    while (testStr[i] != '\0') {
        if (ispunct(testStr[i])) {
            printf("'%c' is a punctuation character.\n", testStr[i]);
        } else {
            printf("'%c' is not a punctuation character.\n", testStr[i]);
        }
        i++;
    }
    
    return 0;
}

Explanation:

1. A string "Hello, World!" is defined.
2. The program iterates over each character in the string.
3. For each character, ispunct() determines if it is a punctuation character.
4. A message is printed indicating whether each character is punctuation or not.

Program Output:

'H' is not a punctuation character.
'e' is not a punctuation character.
'l' is not a punctuation character.
'l' is not a punctuation character.
'o' is not a punctuation character.
',' is a punctuation character.
' ' is not a punctuation character.
'W' is not a punctuation character.
'o' is not a punctuation character.
'r' is not a punctuation character.
'l' is not a punctuation character.
'd' is not a punctuation character.
'!' is a punctuation character.

Example 3: Filtering Out Punctuation from a Sentence

This example demonstrates how to process an entire sentence and filter out all punctuation characters.

Program

#include <stdio.h>
#include <ctype.h>

int main() {
    char sentence[] = "Good morning, world!";
    int i = 0;
    
    printf("Sentence without punctuation: ");
    while (sentence[i] != '\0') {
        if (!ispunct(sentence[i])) {
            printf("%c", sentence[i]);
        }
        i++;
    }
    printf("\n");
    
    return 0;
}

Explanation:

1. A sentence "Good morning, world!" is defined.
2. The program iterates over each character of the sentence.
3. The ispunct() function is used to check if a character is punctuation.
4. If the character is not punctuation, it is printed; punctuation characters are skipped.

Program Output:

Sentence without punctuation: Good morning world