Mini Shell

# Use the original STDIN STDOUT and STDERR when rear was launched by the user
# to get input from the user and to show output to the user (cf. _input-output-functions.sh).
####################### BEGIN Progress Indicator
# Call StartProgressSubsystem to get more detailed progress reports:
if tty -s <&7 ; then
    # There is a tty on the original STDOUT.
    if test "plain" = "$PROGRESS_MODE" ; then
        # The 'plain' progress mode outputs the same content
        # as below but without ANSI escape sequences:
        function ProgressStart () {
            echo "${MESSAGE_PREFIX}$*" 1>&7
        }
        function ProgressStop () {
            echo "${MESSAGE_PREFIX}OK" 1>&7
        }
        function ProgressError () {
            echo "${MESSAGE_PREFIX}FAILED" 1>&7
        }
        function ProgressInfo () {
            echo "${MESSAGE_PREFIX}$*" 1>&7
        }
    else
        # If the 'plain' progress mode is not explicitly requested
        # (default/fallback behaviour when there is a tty on stdout)
        # do progress animated display via ANSI escape sequences,
        # see http://ascii-table.com/ansi-escape-sequences-vt-100.php
        # for the ANSI escape sequences as they appear below:
        #   Esc[2K : Clear entire line
        #   Esc7   : Save cursor position and attributes
        #   Esc8   : Restore cursor position and attributes
        #   Esc[K  : Clear line from cursor right
        function ProgressStart () {
            echo -en "\e[2K\r${MESSAGE_PREFIX}$*\e7" 1>&7
        }
        function ProgressStop () {
            echo -e "\e8\e[K${MESSAGE_PREFIX}OK" 1>&7
        }
        function ProgressError () {
            echo -e "\e8\e[K${MESSAGE_PREFIX}FAILED" 1>&7
        }
        function ProgressInfo () {
            echo -en "\e[2K\r${MESSAGE_PREFIX}$*\e7" 1>&7
        }
    fi
else
    # No tty on the original STDOUT, disable progress animated display altogether.
    # The main difference to the 'plain' progress mode above is that
    # there is no ProgressInfo when there is no tty the original STDOUT:
    function ProgressStart () {
        echo -n "${MESSAGE_PREFIX}$*" 1>&7
    }
    function ProgressStop () {
        echo -e "${MESSAGE_PREFIX}OK" 1>&7
    }
    function ProgressError () {
        echo -e "${MESSAGE_PREFIX}FAILED" 1>&7
    }
fi
####################### END Progress Indicator