Question

In my .bash_profile I have the following lines:

PATHDIRS="
/usr/local/mysql/bin
/usr/local/share/python
/opt/local/bin
/opt/local/sbin
$HOME/bin"
for dir in $PATHDIRS
do
    if [ -d $dir ]; then
        export PATH=$PATH:$dir
    fi
done

However I tried copying this to my .zshrc, and the $PATH is not being set.

First I put echo statements inside the “if directory exists” function and I found that the if statement was evaluating to false, even for directories that clearly existed.

Then I removed the directory-exists check, and the $PATH was being set incorrectly like this:

/usr/bin:/bin:/usr/sbin:/sbin:
/usr/local/bin
/opt/local/bin
/opt/local/sbin
/Volumes/Xshare/kburke/bin
/usr/local/Cellar/ruby/1.9.2-p290/bin
/Users/kevin/.gem/ruby/1.8/bin
/Users/kevin/bin

None of the programs in the bottom directories were being found or executed.
What am I doing wrong?

Answer 1

Unlike other shells, zsh does not perform word splitting or globbing after variable substitution. Thus $PATHDIRS expands to a single string containing exactly the value of the variable, and not to a list of strings containing each separate whitespace-delimited piece of the value.

Using an array is the best way to express this (not only in zsh, but also in ksh and bash).

pathdirs=(
    /usr/local/mysql/bin
    …
    ~/bin
)
for dir in $pathdirs; do
    if [ -d $dir ]; then
        path+=$dir
    fi
done

Since you probably aren’t going to refer to pathdirs later, you might as well write it inline:

for dir in \
  /usr/local/mysql/bin \
  … \
  ~/bin
; do
  if [[ -d $dir ]]; then path+=$dir; fi
done

There’s even a shorter way to express this: add all the directories you like to the path array, then select the ones that exist.

path+=/usr/local/mysql/bin
…
path=($^path(N))

The N glob qualifier selects only the matches that exist. Add the -/ to the qualifier list (i.e. (-/N) or (N-/)) if you’re worried that one of the elements may be something other than a directory or a symbolic link to one (e.g. a broken symlink). The ^ parameter expansion flag ensures that the glob qualifier applies to each array element separately.

You can also use the N qualifier to add an element only if it exists. Note that you need globbing to happen, so path+=/usr/local/mysql/bin(N) wouldn’t work.

path+=(/usr/local/bin/mysql/bin(N-/))