isdigit()

Test a character to see if it's a decimal digit

Synopsis:

#include <ctype.h>

int isdigit( int c );

Arguments:

c: The character you want to test.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The isdigit() function tests for a decimal digit (characters 0 through 9).

Returns:

Nonzero if c is a decimal digit; otherwise, zero.

Examples:

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

char the_chars[] = { 'A', '5', '$' };

#define SIZE sizeof( the_chars ) / sizeof( char )

int main( void )
{
    int i;

    for( i = 0; i < SIZE; i++ ) {
        if( isdigit( the_chars[i] ) ) {
            printf( "Char %c is a digit character\n",
                the_chars[i] );
        } else {
            printf( "Char %c is not a digit character\n",
                the_chars[i] );
        }
    }
    
    return EXIT_SUCCESS;
}

produces the output:

Char A is not a digit character
Char 5 is a digit character
Char $ is not a digit character

Classification:

ANSI, POSIX 1003.1

Safety:
Cancellation point	No
Interrupt handler	Yes
Signal handler	Yes
Thread	Yes