examples/functions/coproc.bash

   1 # coprocess.bash
   2 #
   3 # vi:set sts=2 sw=2 ai:
   4 #
   5
   6 coprocess_pid=
   7
   8 #
   9 # coprocess - Start, control, and end coprocesses.
  10 #
  11 function coprocess ()
  12 {
  13   while (( $# > 0 )) ; do
  14     case "$1" in
  15       #
  16       # coprocess close
  17       #
  18       c|cl|clo|clos|close)
  19         shift
  20         exec 61>&- 62<&-
  21         coprocess_pid=
  22         if [ "$1" = "-SIGPIPE" ] ; then
  23           # Only print message in an interactive shell
  24           case "$-" in
  25             *i*)
  26               echo 'SIGPIPE' >&2
  27               ;;
  28           esac
  29           return 1
  30         fi
  31         return 0
  32         ;;
  33
  34       #
  35       # coprocess open
  36       #
  37       o|op|ope|open)
  38         shift
  39         local fifo="/var/tmp/coprocess.$$.$RANDOM"
  40
  41         local cmd="/bin/bash"
  42         if (( $# > 0 )) ; then
  43           cmd="$@"
  44         fi
  45
  46         mkfifo "$fifo.in" || return $?
  47         mkfifo "$fifo.out" || {
  48           ret=$?
  49           rm -f "$fifo.in"
  50           return $?
  51         }
  52
  53         ( "$@" <$fifo.in >$fifo.out ; rm -f "$fifo.in" "$fifo.out" ) &
  54         coprocess_pid=$!
  55         exec 61>$fifo.in 62<$fifo.out
  56         return 0
  57         ;;
  58
  59       #
  60       # coprocess print - write to the coprocess
  61       #
  62       p|pr|pri|prin|print)
  63         shift
  64         local old_trap=$(trap -p SIGPIPE)
  65         trap 'coprocess close -SIGPIPE' SIGPIPE
  66         if [ $# -eq 1 -a "$1" = "--stdin" ] ; then
  67           cat >&61
  68         else
  69           echo "$@" >&61
  70         fi
  71         local ret=$?
  72         eval "$old_trap"
  73         return $ret
  74         ;;
  75
  76       #
  77       # coprocess read - read from the coprocess
  78       #
  79       r|re|rea|read)
  80         shift
  81         local old_trap=$(trap -p SIGPIPE)
  82         trap '_coprocess_close -SIGPIPE' SIGPIPE
  83         builtin read "$@" <&62
  84         local ret=$?
  85         eval "$old_trap"
  86         return $ret
  87         ;;
  88
  89       s|st|sta|stat|statu|status)
  90         if [ -z "$coprocess_pid" ] ; then
  91           echo 'no active coprocess'
  92           return 1
  93         else
  94           echo "  coprocess is active [$coprocess_pid]"
  95           return 0
  96         fi
  97         ;;
  98
  99       *)
 100         coprocess print "$@"
 101         return $?
 102         ;;
 103     esac
 104     shift
 105   done
 106   coprocess status
 107   return $?
 108 }
 109