A strange, but probably simple, shell_exec issue

Question

If I run this command on the command line (on my Mac OS X):

echo -n "hello" > foo-cmd.txt

I get the expected result, namely a file foo-cmd.txt containing "hello" without any newline at the end.

However, if I run this PHP code:

<?php
shell_exec("echo -n \"hello\" > foo-php.txt");
?>

I get a file foo-php.txt containing the text "-n hello" followed by a newline! In other words, the argument -n sneaks in as output, instead of being treated as an argument!

How can I resolve this issue?

Answer 1

Your command is using the shell's built-in version of echo which doesn't support the -n option.

Try /bin/echo instead.

• Enchilada: How do you figure out (from system to system, or from one PHP version to another) whether shell_exec is using its own built-in version of a particular command?
• Alnitak: @Enchilada it's not shell_exec that has the problem - it's the system shell that shell_exec invokes that has the built-ins. The simple answer is, don't use shell_exec for something that could have been trivially done with a few lines of PHP code.

Answer 2

Try this:

shell_exec("echo\ -n \"hello\" > foo-php.txt");