#! @SHELL@
# tangle-sh: shell script to invoke tangle (or ctangle, etc).
#
#   Copyright (C) 2009 Peter Breitenlohner <tex-live@tug.org>
#
#   This file is free software; the copyright holder
#   gives unlimited permission to copy and/or distribute it,
#   with or without modifications, as long as this notice is preserved.
#
# Tangle may create several files, e.g., tex.p and tex.pool from tex.web
# and tex.ch.  The naive rule
#	tex.p tex.pool: tex.web tex.ch tangle$(EXEEXT)
#		$(tangle) tex tex
# could run 'tangle tex tex' twice in parallel and fail.  To avoid this
# and yet recover from removal of tex.p and/or tex.pool, we use an
# auxiliary stamp file tex-tangle and the two rules
#	tex.p tex.pool: tex-tangle
#		WEBINPUTS=.:$(srcdir) $(SHELL) ./tangle-sh $@ $(TANGLE) tex tex
#	tex-tangle: tex.web tex.ch tangle$(EXEEXT) tangle-sh
#		WEBINPUTS=.:$(srcdir) $(SHELL) ./tangle-sh $@ $(TANGLE) tex tex
# Compare Automake manual (info Automake) 27.9: Multiple Outputs
#
TEXMFCNF=@srcdir@/../kpathsea; export TEXMFCNF

env="TEXMFCNF=$TEXMFCNF"
test "x$WEBINPUTS" = x || env="WEBINPUTS=$WEBINPUTS $env"
test "x$CWEBINPUTS" = x || env="CWEBINPUTS=$CWEBINPUTS $env"

target=$1; shift
tangle=$1; shift
base=$1
stamp=$base-tangle
case $target in
  $stamp)
    # Normal build.
    rm -f $stamp.tmp
    echo timestamp >$stamp.tmp
    echo "$env $tangle $@"
    $tangle "$@" || exit 1
    mv -f $stamp.tmp $stamp
  ;;
  *)
    # Recover from removal of $target
    test -f $target && exit 0
    trap "rm -rf $stamp $stamp.lock" 1 2 13 15
    if mkdir $stamp.lock 2>/dev/null; then
      # Code executed by the first process.
      rm -f $stamp $stamp.tmp
      echo timestamp >$stamp.tmp
      echo "$env $tangle $@"
      $tangle "$@" || exit 1
      mv -f $stamp.tmp $stamp
      rmdir $stamp.lock
    else
      # Code executed by the follower processes.
      # Wait until the first process is done.
      while test -d $stamp.lock; do sleep 1; done
      # Succeed if and only if the first process succeeded.
      test -f $stamp; exit $?
    fi
  ;;
esac

exit 0
