Trailing whitespace in zsh commands

I am writing a zsh script that captures a hostname from file README and ensures that it exists on the network by pinging it. The following is my code:

HOSTNAME=$(cat README 2>/dev/null | grep -oP "^Host(name)*:[\s]+\K(.*)")
ping -w 5 -c 1 $HOSTNAME >/dev/null 2>&1
if [ $? != 0 ]; then
    # error
else
    # all good
fi

I noticed that if the line that contains the hostname in README has a trailing space, ping doesn't work. For example, the line could look like the following where I represent white space with an _ character.

Hostname:____bobscomputer_

Does zsh not get rid of extra whitespace in its commands like bash does?

Solution

You're thinking of word splitting of unquoted variables, which Bash does implicitly but Zsh doesn't. For example:

$ cat test.sh
var="foo bar"
printf '%s\n' $var
$ bash test.sh
foo
bar
$ zsh test.sh
foo bar

If you wanted to do word splitting in Zsh, use $=var.

BTW, here's an awk command that's simpler and avoids the problem (assuming hostnames can't contain whitespace):

HOSTNAME=$(awk '/^Host(name)?:/ {print $2}' README)