_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