isalnum()

Test a character to see if it's alphanumeric

Synopsis:

#include <ctype.h>

int isalnum( int c );

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.

Library:

libc

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

Description:

The isalnum() function tests if the argument c is an alphanumeric character (a to z, A to Z, or 0 to 9). An alphanumeric character is any character for which isalpha() or isdigit() is true.

Returns:

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

Examples:

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

int main( void )
{
    if( isalnum( getchar() ) ) {
        printf( "That's alpha-numeric!\n" );
    }
    
    return EXIT_SUCCESS;
}

Classification:

ANSI, POSIX 1003.1

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

Caveats:

The result is valid only for char arguments and EOF.

Last modified: 2013-12-23

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