iscntrl()

Arguments:

c

The character you want to test. This must be representable as an unsigned char or be EOF; the behavior for other values is undefined. Because this argument is interpreted as an int, to avoid sign extension on character values greater than 0x7F, you must cast the argument to the unsigned data type; otherwise, the function will behave unpredictably.

Library:

libc

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

Description:

The iscntrl() function tests for any control character. An ASCII control character is any character whose value is between 0 and 31.

Returns:

Nonzero if c is a control character; otherwise, zero.

Examples:

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

char the_chars[] = { 'A', 0x09, 'Z' };

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

int main( void )
{
    int i;

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

produces the output:

Char A is not a Control character
Char     is a Control character
Char Z is not a Control character

Classification:

ANSI, POSIX 1003.1