posix_isatty

(PHP 4, PHP 5, PHP 7, PHP 8)

posix_isatty — Determine if a file descriptor is an interactive terminal

Description

posix_isatty(resource|int $file_descriptor): bool

Determines if the file descriptor file_descriptor refers to a valid terminal type device.

Parameters

file_descriptor: The file descriptor, which is expected to be either a file resource or an int. An int will be assumed to be a file descriptor that can be passed directly to the underlying system call.

Return Values

Returns true if file_descriptor is an open descriptor connected to a terminal and false otherwise.

Changelog

Version	Description
8.4.0	Set errno (error number) to `EBADF` when the file descriptor/stream passed is invalid.
8.3.0	Type error `E_WARNING`s are now raised for integer coercions following the usual PHP type coercion semantics.

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User Contributed Notes

hfuecks at phppatterns dot com

20 years ago

Can be useful to determine whether output is being piped elsewhere, for PHP shell scripts, for example;

#!/usr/local/bin/php
<?php
if ( !posix_isatty(STDOUT) ) {
    fwrite(STDOUT, "Invalid TTY\n");
    exit(2);
}
fwrite(STDOUT, "Enter you name\n");
$name = fgets(STDIN);
fwrite(STDOUT,"Hello $name\n");
exit(0);
?>

If this script is like:

script.php > outfile

outfile will contain "Invalid TTY"

KEINOS

4 years ago

It's quite complicated to understand its movements. But it determines if the file_descriptor is open AND connected to a terminal.

Thus, while receiving data from the STDIN, for example, it will return false.

This move is useful to optionally pipe STDIN to a PHP script, to avoid hanging when nothing is from STDIN.

<?php

// Simply echoes the contents from STDIN if any
// and "no stdin" if not.
echo (posix_isatty(STDIN)) ? 'no stdin' . PHP_EOL : file_get_contents('php://stdin');
?>