PHP - detect STDIO input

Question

What I want is being able to optionally pipe STDIO to a PHP script. If not, it'll take input from a file instead. So sometimes I'll simply run the script, other times I'll do something like

grep text logfile | php parseLog.php

I have a loop very much like this and it works fine when STDIO exists:

while (FALSE !== ($line = fgets(STDIN)))
{
        $customLogArr[]=$line;
}

When there's no STDIO though it halts waiting for some, it doesn't even enter the loop.

What I'd like to do is be able to detect if I have STDIO input or not. Is there a way to do that?

KEINOS · Accepted Answer · 2021-01-08 11:44:04Z

3

Using posix_isatty() function might be a little simpler.

posix_isatty | Manual @ PHP.net

<?php

/**
 * parseLog.php
 */

echo (posix_isatty(STDIN)) ? 'no stdin' . PHP_EOL : file_get_contents('php://stdin');

$ echo 'foo' > ./logfile.txt

$ cat logfile.txt | php parseLog.php
foo

$ php parseLog.php
no stdin

posix_isatty(STDIN) determines if the STDIN is open AND connected to a terminal. Thus, while receiving data from the STDIN, it will return false.

REF: https://qiita.com/m_norii/items/cd2d66e5a82c11cac758 @ Qiita (in Japanese)

edited Jan 8, 2021 at 11:44

answered Jan 8, 2021 at 11:05

KEINOS

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Comments

MrMesees · Accepted Answer · 2017-10-16 13:15:07Z

2

looks like something has changed or none of these answers were ever correct. You cannot simply ftell(STDIN) to see if there is data passed from STDIN

<?php

$stdin = fopen('php://stdin', 'r');
var_dump(ftell($stdin));

outputs

-:4:
bool(false)

This is from php -v with output

PHP 7.0.22-0ubuntu0.16.04.1 (cli) ( NTS )
Copyright (c) 1997-2017 The PHP Group
Zend Engine v3.0.0, Copyright (c) 1998-2017 Zend Technologies
    with Zend OPcache v7.0.22-0ubuntu0.16.04.1, Copyright (c) 1999-2017, by Zend Technologies
    with Xdebug v2.4.0, Copyright (c) 2002-2016, by Derick Rethans

when I try to use STDIN constant I get

PHP Notice:  Use of undefined constant STDIN - assumed 'STDIN' in - on line 3

answered Oct 16, 2017 at 13:15

MrMesees

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Comments

AbraCadaver · Accepted Answer · 2015-02-17 21:46:51Z

1

if(FALSE !== ftell(STDIN))
{
    while (FALSE !== ($line = fgets(STDIN)))
    {
        $customLogArr[]=$line;
    }
}

For STDIN, if nothing can be read, ftell() will return false.

edited Feb 17, 2015 at 21:46

AbraCadaver

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answered Feb 17, 2015 at 21:35

grant sun

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4 Comments

DeDee Over a year ago

Last time I checked STDIN position never zeroed on read from STDIN and it was always a non-negative integer so ftell always returns integer.

grant sun Over a year ago

@DeDee Yes,you are right. So false only mean No STDIN for current process.

DeDee Over a year ago

Correct, until STDIN is closed.

MrMesees Over a year ago

php7 @ version 7 PHP 7.0.22-0ubuntu0.16.04.1 (cli) ( NTS ) seems to complain there is no STDIN defined. PHP Notice: Use of undefined constant STDIN - assumed 'STDIN' in - on line 3

DeDee · Accepted Answer · 2015-02-17 21:40:37Z

1

Is this what you're looking for? Forgive me if I misunderstood, this should not hold you when there's no input on STDIN.

stream_set_blocking(STDIN, 1);

function CheckSTDIN() {
    $read = array(STDIN);
    $wrte = NULL;
    $expt = NULL;
    $a = stream_select($read, $wrte, $expt, 0);
    if ($a && in_array(STDIN, $read)) {
        // you can read from STDIN now, it'll only be available if there is anything in STDIN
        // you can return the value or pass it to global or class variable
        return fread(STDIN, 255); // set your desired string length
    } else return false;
}

while (FALSE !== ($line = CheckSTDIN())) {
        $customLogArr[]=$line;
}

edited Feb 17, 2015 at 21:40

answered Feb 17, 2015 at 21:30

DeDee

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6 Comments

DeDee Over a year ago

Strange it does not work for you, I extracted it from my OOP project for which it works the way I described.

AbraCadaver Over a year ago

I reran, yes but: fread() expects exactly 2 parameters, 1 given

DeDee Over a year ago

Oh, I assumed second one is some default, I use 1 in my case, it's an example though of how the stream content can be retrieved. EDIT: fixed fread.

DeDee Over a year ago

@ErickRobertson In the comment above I said I extracted it from my own project. It was a Windows Apache project. It sure worked.

Erick Robertson Over a year ago

I don't have Apache. I just have Windows. It doesn't work on Windows. You need either Apache or Linux.

|

helvete · Accepted Answer · 2021-01-04 15:39:55Z

Consider a script like this:

#!/usr/bin/env php                                                              
<?php                                                                           
                                                                                
$fhandle = fopen("php://stdin", 'r');                                           
$stdinData = ftell($fhandle) === false // strict comparison required                             
    ? null                                                                      
    : stream_get_contents($fhandle);                                            
var_dump($stdinData);

The sript outputs this when no stdin data provided:

$ ./test.php 
NULL

The sript outputs this when stdin data provided:

$ ./test.php < ./test.php 
string(173) "#!/usr/bin/env php
<?php

$fhandle = fopen("php://stdin", 'r');
$stdinData = ftell($fhandle) === false // strict comparison required
    ? null
    : stream_get_contents($fhandle);
var_dump($stdinData);
"

The important part is to use strict comparison (===) as ftell returns pointer position that has a value of 0 in case the handle has just been initialized.

For PHP 7.3 and earlier slightly different approach has to be utilized:

#!/usr/bin/env php
<?php

stream_set_blocking(STDIN, 0);
$stdinData = ftell(STDIN) === false // strict comparison required
    ? null
    : stream_get_contents(STDIN);
var_dump($stdinData);

Kuti Imre · Accepted Answer · 2015-02-17 21:32:44Z

-1

The above solution didn't work for me. This is one that works.

if ($args = stream_get_contents(fopen("php://stdin", "r"))) {

    var_dump($args);

} else {
    echo 'No input';
}

Note: This will read the data piped to the script as a string: echo "Hello World" | php test.php will output string(12) "Hello World" (+ the new line at the end...) So you need to further process the data to an array if that is required. explode() seems to be a simple approach.

answered Feb 17, 2015 at 21:32

Kuti Imre

11 bronze badge

3 Comments

AbraCadaver Over a year ago

But it hangs when nothing is one STDIN. That's what OP is trying to get around.

Arkandel Over a year ago

Correct, this won't work when there's no STDIN unfortunately. I wish. :)

MrMesees Over a year ago

The problem is trying to get contents without ftell($resource) first. Most of the code on this page works if you just know what you are doing and why.

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