how to make a shell script function able to either specify arguments in command line or get them from a pipe?

Question

For example, I want to write a function called fooFun , which will do some process on a PDF file. I'd like to make it able to run on both of the ways as following:

  $ fooFun foo.pdf
  $ ls *.pdf | fooFun

Any ideas? Thanks.

Answer 1

I don't think you can easily do this with a shell function. A better idea is to make it a script, let it take command line arguments, and achieve the second style with xargs :

 ls *.pdf | xargs fooFun

Answer 2

I agree with @larsmans, better to stick with passing arguments as parameters. However, here's how to achieve what you're asking:

foofun() {
  local args arg 
  if [[ $# -eq 0 ]]; then
    args=()
    # consume stdin
    while IFS= read -r arg; do args+=($arg); done
  else
    args=("$@")
  fi
  # do something with "${args[@]}"
}