New frontend demo skript frontend/sh_on_named_pipes.sh
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frontend/sh_on_named_pipes.sh
Executable file
304
frontend/sh_on_named_pipes.sh
Executable file
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#!/bin/bash
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#
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# Demo of a shell frontend that communicates with a xorriso slave via
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# two named pipes.
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#
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# This script creates two named pipes and starts xorriso with command
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# -named_pipes_loop cleanup /tmp/xorriso_stdin_pipe_$$ xorriso_stdin_pipe_$$ -
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# Its main loop prompts the user for commands, sends them to xorriso,
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# receives the replies, and parses them by xorriso command
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# -msg_op parse_silently. The resulting words are printed to stdout.
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#
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# xorriso removes the two pipes when it finishes execution of -named_pipes_loop
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# regularly. (E.g. because of commands -end or -rollback_end or because of
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# name loop control message "end_named_pipe_loop".)
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# The vanishing of the pipe files tells this script that xorriso is gone.
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#
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#
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# Copyright (C) 2013
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# Thomas Schmitt <scdbackup@gmx.net>, libburnia-project.org
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# Provided under BSD license: Use, modify, and distribute as you like.
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#
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# What xorriso program to use
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xorriso=xorriso
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if test o"$1" = o"-xorriso"
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then
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xorriso="$2"
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fi
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# Version of xorriso and minimum requirement by this script
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export xorriso_version=
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export xorriso_version_req=1.3.1
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# Info about the xorriso slave process
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export xorriso_is_running=0
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export xorriso_pid=0
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export xorriso_will_end=0
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# Will be set to 1 before this script ends normally
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export normal_end=0
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# ---------------- An interpreter for quoted xorriso replies ----------------
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# xorriso commands like -lsl wrap filenames into quotation marks in order
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# to unambigously represent any character byte except the 0-byte.
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# This piece of code parses input strings into words by letting xorriso
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# command -msg_op "parse_silently" do the hard work.
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# The input strings should be composed by concatenating input lines with
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# newline characters inbetween. Begin by submitting a single line (without
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# newline at its end) and retry with an appended further line, if
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# xorriso_parse
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# returns 1. See below xorriso_cmd_and_handle_result() for an example.
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# The parsed reply words.
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# Valid are reply_array[0] to reply_array[reply_count-1)]
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export reply_array
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export reply_count
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# Interpret reply of -msg_op parse
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xorriso_recv_parse_reply() {
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reply_count=0
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unset reply_array
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export reply_array
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ret=-1
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read ret
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if test "$ret" -lt 0 -o -z "$ret"
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then
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echo "Unexpected text as first reply line of -msg_op parse" >&2
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xorriso_is_running=0
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return 2
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fi
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test "$ret" = 0 && return "1"
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read num_strings
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string_count=0
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while true
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do
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test "$string_count" -ge "$num_strings" && break
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read num_lines
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line_count=0
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acc=
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while true
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do
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test "$line_count" -ge "$num_lines" && break
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read line
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test "$line_count" -gt 0 && acc="$acc"$'\n'
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acc="$acc""$line"
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line_count=$(($line_count + 1))
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done
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reply_array["$string_count"]="$acc"
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string_count=$(($string_count + 1))
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done
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reply_count="$num_strings"
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return 0
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}
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# Parse a quoted multi-line string into words
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xorriso_parse() {
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# $1 : The string which shall be parsed
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# $2 : The number of concatenated input lines (= number of newlines + 1)
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# return: 0= array is valid , 1= line incomplete , 2= other error
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test "$xorriso_is_running" = 0 && return 1
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xorriso_send_cmd "msg_op parse_silently "'"'"'' '' 0 0 $2"'"'$'\n'"$1" || \
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return 2
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xorriso_recv_parse_reply <"$result_pipe" || xorriso_is_running=0
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ret=$?
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test "$xorriso_is_running" = 0 && ret=2
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return "$ret"
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}
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# ------------- End of interpreter for quoted xorriso replies --------------
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# Send one or more command lines to xorriso
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xorriso_send_cmd() {
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# $1 : the lines to send
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# >>> is it possible to have a timeout on echo ?
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if test -p "$cmd_pipe"
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then
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echo -E "$1" >"$cmd_pipe"
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else
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xorriso_is_running=0
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return 1
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fi
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}
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# Make filenames safe for transport by wrapping them in quotes and
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# escaping quotes in their text
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xorriso_esc() {
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echo -n "'"
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echo -n "$1" | sed -e "s/'/'"'"'"'"'"'"'/g"
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echo -n "'"
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}
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# A handler function for xorriso_cmd_and_handle_result
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xorriso_reply_to_stdout() {
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echo "${reply_array[*]}"
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}
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# Let a handler inspect the result lines of a xorriso command line
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xorriso_cmd_and_handle_result() {
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# $1: handler command word and possibly argument words
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# $2: command line for xorriso
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if test "$xorriso_is_running" = 0
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then
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return 1
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fi
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handler="$1"
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xorriso_send_cmd "$2" || return 1
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res=$(cat "$result_pipe")
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ret=$?
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if test "$xorriso_will_end" = 1 -o "$xorriso_is_running" = 0 -o "$ret" -ne 0
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then
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test -n "$res" && echo -n "$res"
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xorriso_is_running=0
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test "$ret" = 0 || return 1
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return 0
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fi
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test -z "$res" && return 0
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echo "$res" | \
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while read line
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do
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line_count=1
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while true
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do
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xorriso_parse "$line" "$line_count"
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ret=$?
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test "$ret" = 0 && break
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if test "$ret" = 2
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then
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return 1
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fi
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read addon
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line="$line"$'\n'"$addon"
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line_count=$(expr "$line_count" + 1)
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done
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# One can now make use of reply_array[0...(reply_count-1)]
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$handler
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done
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return 0
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}
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# Execute -version and let xorriso_version_handler interpret reply
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xorriso_check_version() {
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lookfor='^xorriso version : '
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xorriso_version=$("$xorriso" -version 2>/dev/null | grep "$lookfor" | \
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sed -e "s/${lookfor}//")
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ret=$?
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if test "$ret" -ne 0 -o "$xorriso_version" = ""
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then
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echo "SORRY: Program run '${xorriso}' -version did not yield a result." >&2
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echo >&2
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exit 2
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fi
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smallest=$((echo "$xorriso_version_req" ; echo "$xorriso_version" ) | \
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sort | head -1)
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test "$smallest" = "$xorriso_version_req" && return 0
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echo "SORRY: xorriso version too old: ${xorriso_version} . Need at least xorriso-${xorriso_version_req} ." >&2
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echo >&2
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exit 2
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}
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# To be executed on exit
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xorriso_cleanup() {
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send_end_cmd=0
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if test -p "$cmd_pipe" -a "$xorriso_is_running" = 1
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then
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if test "$normal_end" = 0
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then
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echo "Checking whether xorriso is still running ..." >&2
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set -x
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# Give xorriso time to abort
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sleep 1
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if ps | grep '^'"$xorriso_pid" >/dev/null
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then
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# >>> try to further confirm xorriso identity
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send_end_cmd=1
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fi
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else
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send_end_cmd=1
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fi
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fi
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test "$normal_end" = 0 && set -x
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if test "$send_end_cmd" = 1
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then
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echo "Sending xorriso an -end command ..." >&2
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xorriso_send_cmd "end" && \
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test -p "$result_pipe" && cat "$result_pipe" >/dev/null
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fi
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test -p "$cmd_pipe" && rm "$cmd_pipe"
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test -p "$result_pipe" && rm "$result_pipe"
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}
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# ---------------------------------- main ---------------------------------
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# Choose pipe names
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export cmd_pipe=/tmp/xorriso_stdin_pipe_$$
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export result_pipe=/tmp/xorriso_stdout_pipe_$$
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# Check the program whether it is modern enough
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xorriso_check_version "$xorriso"
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# Prepare for then end of this script
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trap xorriso_cleanup EXIT
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# Create the pipes and start xorriso
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mknod "$cmd_pipe" p
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mknod "$result_pipe" p
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"$xorriso" -abort_on NEVER -for_backup \
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-named_pipe_loop cleanup:buffered "$cmd_pipe" "$result_pipe" "-" &
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xorriso_pid=$!
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xorriso_is_running=1
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# Get a sign of life from xorriso before issueing the loop prompt
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xorriso_cmd_and_handle_result xorriso_reply_to_stdout \
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"print_info 'xorriso process ${xorriso_pid} started by $0'"
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echo >&2
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# Now get commands from the user, send them to xorriso and display them
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# via the simple handler xorriso_reply_to_stdout()
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while test "$xorriso_is_running" = 1
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do
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if test -p "$cmd_pipe"
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then
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echo -n "xorriso> " >&2
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else
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echo "$0 : Lost contact to xorriso process $xorriso_pid" >&2
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xorriso_is_running=0
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break
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fi
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read line
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if echo "$line" | grep '^-*end$' >/dev/null
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then
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break
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fi
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if echo "$line" | grep '^-*rollback_end$' >/dev/null
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then
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xorriso_will_end=1
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fi
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xorriso_cmd_and_handle_result xorriso_reply_to_stdout "$line"
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done
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# Prevent set -x in the exit handler
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normal_end=1
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