More examples of hard-coded file descriptors

spec/hard-coded-descriptors.sh

@@ -9,6 +9,14 @@ set -o nounset
set -o pipefail
set -o errexit

# https://lobste.rs/s/bqftd6/avoid_directly_manipulating_file
#
# - "One thing that I have found non-{0,1,2} FDs useful for however is when
#   tools (e.g. gpg) take a --passphrase-fd argument, useful for when you are
#   also redirecting some other thing into stdin."
# - "Some protocols (like djb’s checkpassword or doit) rely on specific file
#   descriptors"

# https://www.reddit.com/r/bash/comments/6td8j2/avoid_directly_manipulating_file_descriptors_in/

interactive-stdin() {
@@ -42,7 +50,6 @@ tee-like() {
  cat $log
}

# Hm this one isn't working yet
pipe-stderr() {
  local log=_tmp/pipe-stderr.log
  set +o errexit
@@ -76,4 +83,38 @@ zip-demo() {
  _zip _tmp/{left,right}.txt 
}


_work() {
  local id=$1
  echo "Job $id"
  for i in 1 2 3; do
    echo "... $i ..."
    sleep 0.2
  done
}

# man flock
_flock() {
  (
    flock -n 9 || {
      echo "Another job is already running; aborting"
      exit 1
    }
    "$@"

  ) 9>_tmp/mylockfile
}

flock-demo() {
  _work A
  _work B

  # Instead of running
  $0 _flock _work C &
  $0 _flock _work D &  # One is already running
  wait
  wait
}


"$@"