zsh vs bash difference in for loop, what is the zsh way?

Question

Suppose there is a simple script. ``` for file in `hadoop classpath | tr ':' ' ' | sort | uniq`; do echo $file; done ``` and the original output of `hadoop classpath` looks like this (the list of folders where to look for the jars): ``` zsh %> hadoop classpath /usr/local/hadoop/etc/hadoop:/usr/local/hadoop/share/hadoop/common/lib/*:/usr/local/hadoop/share/hadoop/common/*:/usr/local/hadoop/share/hadoop/hdfs:/usr/local/hadoop/share/hadoop/hdfs/lib/*:/usr/local/hadoop/share/hadoop/hdfs/*:/usr/local/hadoop/share/hadoop/yarn/lib/*:/usr/local/hadoop/share/hadoop/yarn/*:/usr/local/hadoop/share/hadoop/mapreduce/lib/*:/usr/local/hadoop/share/hadoop/mapreduce/*:/usr/local/hadoop/contrib/capacity-scheduler/*.jar ``` If I run the above script in Bourne shell, the results will be like this (which will give the unique list of all jars contained in the specified classpath): ``` bash-4.1$ for file in `hadoop classpath | tr ':' ' ' | sort | uniq`; do echo $file; done /usr/local/hadoop/etc/hadoop /usr/…

Accepted Answer

Unlike Bourne shell, zsh does not perform filename generation after expanding a parameter. I.e. `$x` means exactly what it says, the value of the variable `x` passed on as one argument without splitting or filename expansion. To force whitespace splitting, use `${=x}` or invoke `setopt sh_word_split`. To force filename expansion, use `${~x}` or invoke `setopt glob_subst`. To prevent zsh from complaining when a directory contains no files, use the `(N)` modifier that sets the `NULL_GLOB` option for the duration of the pattern.

Combining all these results in:

```
classpath=$(hadoop classpath | tr ':' ' ' | sort | uniq)
for file in ${=~classpath}(N); do
  echo $file
done
```

Note that `sort | uniq` can be shortened to `sort -u` if you're using GNU sort (the default on Linux).

zsh vs bash difference in for loop, what is the zsh way?

Solution

Problem