_isatty

Determines whether a file descriptor is associated with a character device.

Syntax

int _isatty( int fd );

Parameters

fd
File descriptor that refers to the device to be tested.

Return value

_isatty returns a nonzero value if the descriptor is associated with a character device. Otherwise, _isatty returns 0.

Remarks

The _isatty function determines whether fd is associated with a character device (a terminal, console, printer, or serial port).

This function validates the fd parameter. If fd is a bad file pointer, the invalid parameter handler is invoked, as described in Parameter validation. If execution is allowed to continue, the function returns 0 and sets errno to EBADF.

By default, this function's global state is scoped to the application. To change this behavior, see Global state in the CRT.

Requirements

Routine	Required header
_isatty	<io.h>

For more compatibility information, see Compatibility.

Libraries

All versions of the C run-time libraries.

Example

// crt_isatty.c
/* This program checks to see whether
* stdout has been redirected to a file.
*/

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

int main( void )
{
   if( _isatty( _fileno( stdout ) ) )
      printf( "stdout has not been redirected to a file\n" );
   else
      printf( "stdout has been redirected to a file\n");
}

Sample output

stdout has not been redirected to a file

See also

File handling