# PHP output piped to ‘less’ is requiring after every command

lessphp-clipipe

Piping PHP output to the linux 'less' command causes 'less' to really act up. (CentOS 6.2, didn't happen with CentOS 5.)

When I pipe output from php into 'less', it requires the enter key be pressed after every command, even after the 'j' command (the command to scroll down one line). In addition, the command key is showing up on-screen, and 'less' isn't cleaning up the screen.

So, after running:

$php -r 'for ($i=0; $i<300;$i++) { print "$i\n";}' | less  and then typing j (which usually scrolls down one line), I see a 'j' character showing up at the bottom of the screen after the ':' character. Pressing enter causes less to finally "take" the j command, and it does indeed scroll, but now I see the ":j" between two adjacent lines of the output: 10 :j 11  When using less with the equivalent output from python, everything is fine and less acts normally: $ python -c 'for i in xrange(1, 300): print i' | less


What's going on and how do I fix it?

$less --version less 436 Copyright (C) 1984-2009 Mark Nudelman less comes with NO WARRANTY, to the extent permitted by law. For information about the terms of redistribution, see the file named README in the less distribution. Homepage: http://www.greenwoodsoftware.com/less$ php --version
PHP 5.3.27 (cli) (built: Aug 26 2013 11:46:37)
Copyright (c) 1997-2013 The PHP Group
Zend Engine v2.3.0, Copyright (c) 1998-2013 Zend Technologies


I'm using Terminal.app on Mac OS X to ssh to the box, then running the php command.

Edit:

Found the solution: You need to do a < /dev/null after the PHP command:

php -r 'for ($i=0;$i<300; $i++) { print "$i\n";}' < /dev/null | less


Apparently PHP behaves differently because it still expects input from stdin.
With the < /dev/null you force PHP into thinking there is no further input.

Edit 2:

If you don't want to (keep) typing the < /dev/null you can create an alias for php2 or something:

alias php2="php < /dev/null


You can make this permanent if you add it in your ~/.bashrc.

Now you can do:

php2 -r 'for ($i=0;$i<300; $i++) { print "$i\n";}' | less


You could alias php to itself but then you'll never have the ability to pipe something into php.
You could of course shorten it to p (for less typing).

The bug is also present in CentOS 6.5.

A newly installed CentOS 6.5 has it too (in a VM). A ... | cat | less does not work.
A ... > a && cat a | less does work. Go figure.

Cursor keys also don't work in php --help | less. They do work in python --help | less. So it must be something in the PHP executable. I think this is a longstanding bug in PHP.

I found a reference to this bug here.

Until it is fixed you need to do a redirect:

php -r 'for ($i=0;$i<300; $i++) { print "$i\n";}' > /tmp/php.txt && cat /tmp/php.txt | less
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