slice.sh

#!/usr/bin/env bash
#
# slice.sh - split stdin lines into chunks and run given commands
#
# Examples: Run given commands once per 2 lines
#
# ```sh
# { echo foo
#   echo bar
#   echo baz
# } | ./slice.sh -n2 sh -c 'echo $$; cat'
# 94245
# foo
# bar
# 94251
# baz
# ```
#

set -e -o pipefail

n=1

while [ "$#" -gt 0 ]; do
  case "$1" in
  "-n"* )
    if [[ "$1" == "-n" ]]; then
      n="$2"
      shift 1
    else
      n="${1#-n}"
    fi
    ;;
  * )
    break
    ;;
  esac
  shift 1
done

TMPDIR="$(mktemp -d "${TMP:-/tmp}/${0##*/}.XXXXXXXX")"
on_exit() { rm -fr "${TMPDIR}"; }
trap on_exit EXIT

cat > "${TMPDIR}/stdin"

total="$(cat "${TMPDIR}/stdin" | wc -l)"

for slice in $(seq 1 "${n}" "${total}"); do
  cat "${TMPDIR}/stdin" | tail -n "+${slice}" | head -n "${n}" > "${TMPDIR}/slice${slice}"
  cat "${TMPDIR}/slice${slice}" | "$@"
done

# vim:set ft=sh :