isalpha()

Test a character to see if it's alphabetic

Synopsis:

#include <ctype.h>

int isalpha( 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 isalpha() function tests if the argument c is an alphabetic character (a to z and A to Z). An alphabetic character is any character for which isupper() or islower() is true.

Returns:

Nonzero if c is an alphabetic character; otherwise, zero.

Examples:

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

int main( void )
{
    if( isalpha( getchar() ) ) {
      printf( "That's alphabetic\n" );
    }
    
    return EXIT_SUCCESS;
}

Classification:

ANSI, POSIX 1003.1

Safety:
Cancellation pointNo
Interrupt handlerYes
Signal handlerYes
ThreadYes

Related links

  • isalnum()

    Test a character to see if it's alphanumeric

  • isblank()

    Test a character to see if it's a blank character

  • iscntrl()

    Test a character to see if it's a control character

  • isdigit()

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

  • isgraph()

    Test a character to see if it's any printable character except a space

  • islower()

    Test a character to see if it's a lowercase letter

  • isprint()

    Test a character to see if it's any printable character, including a space

  • ispunct()

    Test a character to see if it's any punctuation character

  • isspace()

    Test a character to see if it's a whitespace character

  • isupper()

    Test a character to see if it's an uppercase letter

  • iswalpha()

    Test a wide character to see if it's alphabetic

  • isxdigit()

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

  • tolower()

    Convert a character to lowercase

  • toupper()

    Convert a character to uppercase