Lazy script to run ag and entr in conjunction with a series of commands.

agentr

#!/usr/bin/env bash

prog="$(basename "$0")"

want() {
  for bin; do
    if ! hash "$bin" 1>/dev/null 2>&1; then
      echo "$bin: not installed" 1>&2
      exit 1
    fi
  done
}

want ag entr

usage() {
  exec 1>&2
  cat 1>&2 <<EOF
${prog} [TYPE...] :: CMD[, CMD...]

TYPE
  One of the type names understood by ag (e.g., go, c, md, erl). May
  also be used to pass long arguments to ag (such as 'erl
  skip-vcs-ignores') as these are passed directly to ag with '--'
  prefixes.

  If no type is given, then all files will be listed.

CMD
  One or more comma-and-space separated commands to execute if a file is
  changed. Commands are executed in a new shell.
  Comma-separated commands such as 'CMD1, CMD2, CMD3' are executed as
  'CMD1 && CMD2 && CMD3'.
  Strings are passed verbatim (after expansion from the shell) to the
  subshell for commands, so special characters will require
  double-quoting to escape them (e..g, "'>'" to pass a > as text).
  Commas can be escaped by writing a second comma (e.g., 'x,,').
EOF
  exit 2
}

entrargs=()
agargs=()

case "$1" in
-h|-help|--help) usage;;
esac

while [ $# -gt 0 ]; do
  if [[ "$1" =~ ^-[cdnprs]+$ ]]; then
    entrargs[${#entrargs[@]}]="$1"
    shift
    continue
  fi

  case "$1" in
  ::)
    break
    ;;
  '')
    shift
    ;;
  --*)
    agargs[${#agargs[@]}]="$1"
    shift
    ;;
  [a-z0-9]*)
    agargs[${#agargs[@]}]="--$1"
    shift
    ;;
  esac
done

if [ $# -eq 1 ]; then
  echo "$prog: no command(s) found after separator (::)" 1>&2
  exit 1
elif [ $# -eq 0 ]; then
  echo "$prog: no separator (::) found" 1>&2
  exit 1
fi
shift

argv=()
for arg; do
  case "$arg" in
  *,,) argv=("${argv[@]}" "${arg%,}");;
  ,)   argv=("${argv[@]}" '&&');;
  *,)  argv=("${argv[@]}" "${arg%,}" '&&');;
  *)   argv=("${argv[@]}" "${arg}");;
  esac
done

# Default to bash is no shell set
: "${SHELL:=bash}"
while :; do
  ag "${agargs[@]}" -l | entr "${entrargs[@]}" "$SHELL" -c "${argv[*]}" "$SHELL"
  sleep 1 || break
done

Quick examples:

# Run go tests and build(s)
$ agentr go :: go test ./..., go build ./cmd/foo

# Run eunit and dialyzer when erlang sources change (uses comma escaping)
$ agentr erl :: rebar3 do eunit,, dialyzer

# Rebuild HTML for markdown
$ agentr md :: kramdown README.md \> README.html