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isatty
NAME
isatty - Is a file descriptor a TTY ?
SYNOPSIS
int r = isatty(fd);
int fd;
FUNCTION
Returns TRUE (1) if the file descriptor is associated with a
console, FALSE (0) if not, or -1 if an error condition occurs
(such as illegal file descriptor).
NOTE
the standard input (0), standard output (1), and standard error (2)
can all return different values for isatty() depending on how the
program is redirected. A program whos standard in and standard out
is redirected may still have a standard error that is connected to
the console.
refer to the file_descriptor manual page for general information
Unlike file pointers and file handles, the file descriptor is
checked for validity and will simply return an error if illegal.
EXAMPLE
#include <stdio.h>
main()
{
if (isatty(1)) {
puts("input is a TTY");
} else {
puts("input is not a TTY");
}
}
1> testprg
input is a TTY
1> echo >t:x ; create dummy file
1> testprg <t:x
input is not a TTY
1>
INPUTS
int fd; file descriptor
RESULTS
int r; result, 1 if a tty, 0 if not, or -1 if error