### isatty -- Test Handle for Character Device

Format

>     #include <io.h>
>     int isatty(int handle);

Language Level: XPG4, Extension
isatty determines whether the given handle is associated with a character device (a keyboard, display, or printer or serial port).

Note: In earlier releases of the C/C++ run-time library, isatty began with an underscore (_isatty). Because it is defined by the X/Open standard, the underscore has been removed. For compatibility, IBM C and C++ Compilers will map _isatty to isatty for you.

Return Value
isatty returns a nonzero value if the device is a character device. Otherwise, the return value is 0.

Example
This example opens the console and determines if it is a character device:

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

    int main(void)
    {
       int fh;

       if (-1 == (fh = fileno(stdin))) {
          perror("Error getting file handle from stdin.\n");
          return EXIT_FAILURE;
       }

       if (0 != isatty(fh))
          printf("stdin is a character device.\n");
       else
          printf("stdin is not a character device.\n");

       return 0;

       /***************************************************
          The output should be:

          stdin is a character device.
       ***************************************************/
    }

_inp -- Read Byte from Input Port
_inpd -- Read Doubleword from Input Port
_inpw -- Read Unsigned Short from Input Port
_outp -- Write Byte to Output Port
_outpd -- Write Double Word to Output Port
_outpw -- Write Word to Output Port
<io.h>