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int _isatty(
   int fd 


File descriptor referring to device to be tested.

Return Value

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


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


Routine Required header Compatibility
_isatty <io.h> Win 98, Win Me, Win NT, Win 2000, Win XP

For additional compatibility information, see Compatibility in the Introduction.


All versions of the C run-time libraries.


// 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" );
      printf( "stdout has been redirected to a file\n");

Sample Output

stdout has not been redirected to a file

See Also

File Handling Routines | Run-Time Routines and .NET Framework Equivalents

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