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chrishiestand
Asked: 2013-04-12 14:11:15 +0800 CST

In zsh, how do you redirect stderr to /dev/null within a for or foreach loop?

  • 772

I am trying to accomplish something that is easy in bash: look for files in a folder and source them if they exist (and do not output if no files exist).

In bourne shells this is how to do it:

  if [ -d /etc/profile.d ]; then
      for f in `ls -1 /etc/profile.d/*.sh 2> /dev/null`; do
          . $f
      done
  fi

I am new to zsh and cannot get the equivalent working. What am I doing wrong?

if [[ -d "/etc/zsh.d" ]]; then
    for file in (ls -1 /etc/zsh.d/*.zsh 2> /dev/null); do
        source $file
    done
fi

fail: parse error near '>'.

I have tried many variations and cannot get it to be as smooth as the sh/bash equivalent. It's as if redirection does not always work within subshells.

shell-scripting

3 Answers

  1. Best Answer

    After a later email to the zsh users mailing list, I was given the nearly ideal solution to the problem:

    if [[ -d "/etc/zsh.d" ]]; then
  for f in /etc/zsh.d/*.zsh(N); do
    source $f
  done
fi

    The (N) tells zsh to set the NULL_GLOB option for that pattern. When no matches are found, the glob expands to an empty string instead of throwing an error. In zsh a for loop over an empty expansion does nothing, which is the behavior we want here.

    • 4

  2. Parsing ls is a bad idea.

    Instead you can just use shell globbing to get a list of files:

    if [[ -d "/etc/zsh.d" ]]; then
  for f in /etc/zsh.d/*.zsh; do
    source $f
  done
fi

    As for the redirection, I'm not sure what the purpose of it is in your example, but if you use this method then it's the shell that might throw an error, not ls, so perform the redirection after done in the for loop.

    • 3

  3. I hope you understand that nearly all sh syntax works just fine in zsh?

    # Check dir exists then that there are files in it (silently!)
# If there are no .zsh files in /etc/zsh.d then an empty argument
# is passed to for, which then simply skips the loop

if [ -d /etc/zsh.d ]; then
    for file in $(find /etc/zsh.d/ -name '*.zsh'); do
        source $file
    done
fi

    I've tried to make it as fast as possible, since you're in a login script.

    This should work for the whole Bourne family.

    • 1