How to check if bash input is being redirect to PHP script?

Question

I'm writing a PHP script and I would like to be able to optionally use a file as the script input. This way:

$ php script.php < file.txt

I'm, actually, able to do that using file_get_contents:

$data = file_get_contents('php://stdin');

However, if I don't pass a file to the input, the scripts hangs indefinetelly, waiting for an input.

I tried the following, but it didn't work:

$data = '';
$in = fopen('php://stdin', 'r');
do {
    $bytes = fread($in, 4096);
    // Maybe the input will be empty here?! But no, it's not :(
    if (empty($bytes)) {
        break;
    }
    $data .= $bytes;
} while (!feof($in));

The script waits for fread to return a value, but it never returns. I guess it waits for some input the same way file_get_contents does.

Another attempt was made by replacing the do { ... } while loop by a while { ... }, checking for the EOF before than trying to read the input. But that also didn't work.

Any ideas on how can I achieve that?

@JustOnUnderMillions maybe I'm asking too much from PHP client, but there are other non-PHP command-line programs that implement this logic – reads the input or ignores/exits. — Gustavo Straube
– Gustavo Straube, Commented Apr 7, 2017 at 14:18
yep, you are right. I was on the wrong lane. @Alex Howansky gots it. — JustOnUnderMillions
– JustOnUnderMillions, Commented Apr 7, 2017 at 14:20

Alex Howansky · Accepted Answer · 2017-04-07 14:14:39Z

3

You can set STDIN to be non-blocking via the stream_set_blocking() function.

function stdin()
{
    $stdin = '';
    $fh = fopen('php://stdin', 'r');
    stream_set_blocking($fh, false);
    while (($line = fgets($fh)) !== false) {
        $stdin .= $line;
    }
    return $stdin;
}

$stdin = stdin(); // returns the contents of STDIN or empty string if nothing is ready

Obviously, you can change the use of line-at-a-time fgets() to hunk-at-a-time fread() as per your needs.

edited Apr 7, 2017 at 14:14

answered Apr 7, 2017 at 14:10

Alex Howansky

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3 Comments

hassan Over a year ago

as i understood from the OP , i think it's not about blocking IO , it's about checking the input if isset or not , 'However, if I don't pass a file to the input, the scripts hangs indefinetelly, waiting for an input.'

Alex Howansky Over a year ago

Right -- this technique will alleviate that issue. If no input is available on STDIN, this function will immediately return an empty string.

Gustavo Straube Over a year ago

@AlexHowansky, it worked the way I wanted. I didn't know about stream_set_blocking function.

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