d2u (bashisms)

#!/bin/bash
# dos to unix converter
# changes dos line endings to unix line endings

# control eol chars
CR="\15"
LF="\32"
CRLF="\15\32"


DEBUG_MODE=

function check_stdin
{
    [[ -t 0 ]] && \
    echo 'STDIN is attached to TTY'

    [[ -p /dev/stdin ]] && \
    echo 'STDIN is attached to a pipe'

    [[ ! -t 0 && ! -p /dev/stdin ]] && \
    echo 'STDIN is attached to a redirection'
}


function check_stdout
{
    [[ -t 1 ]] && \
    echo 'STDOUT is attached to TTY'

    [[ -p /dev/stdout ]] && \
    echo 'STDOUT is attached to a pipe'

    [[ ! -t 1 && ! -p /dev/stdout ]] && \
    echo 'STDOUT is attached to a redirection'
}


[[ $DEBUG_MODE ]] && echo "DEBUG MODE" && check_stdin  &&  check_stdin  &&  exit

DONE=

TR=$(which tr)

if [[ ! "${TR}" ]]
then
    echo -e "ERROR -- can;t find tr binary in executable path."
    usage
    exit -1
fi

if [[ ! $TEMPDIR ]]
then
    TEMPDIR="/tmp"
fi




if [ -t 0 ]
then
#    echo "terminal input"
    TERMIN=1
fi

if [ -t 1 ]
then
#    echo "terminal output"
    TERMOUT=1
fi



# don't automatically overwrite files
check_overwrite()
{
    read -p "overwrite existing file ${1} ? [Y]" do_overwrite

    do_overwrite=${do_overwrite,,}    # tolower

    if [[ $do_overwrite =~ ^(yes|y)$ ]] ; then
    return 1
     else
    return 0
    fi
}


# help
usage()
{
    cat <<EOF
Usage:   d2u  <file>
                    if no outfile is specified,
                    <textfile> is overwritten.

         d2u  <inputfile> <outputfile>

         [file output] | d2u | [file input]
                    use d2u as a text filter

EOF

}



if [ "X${1}" == "Xhelp" ] ; then
    usage
    exit 0
fi


if [ $# -gt 2 ] ; then
    usage
    exit -1
fi


if [ ! -f "${1}" ]
then

    # filter just  tr <stdin> tr <stdout>
    if [[ ! $DONE ]] && [[ $TERMIN ]] && [[ $TERMOUT ]]
    then
    ${TR} -d '\15\32'
    DONE=1
    fi

    # translate a pipe
    if [[ ! $DONE ]] && [[ $TERMOUT ]] && [[ ! $TERMIN ]]
    then

    ${TR} -d '\15\32'

    DONE=1
    fi

fi



# translate a file
if [[ ! $DONE ]] && [[ $TERMIN ]] && [ -f "${1}" ]
then
    newfile="${TEMPDIR}/tr.temp"
    ${TR} -d '\15\32' < "${1}" > "${newfile}"

    if [ -e "${newfile}" ]; then
    mv "${1}"  "${1}.tr.old"
    mv "${newfile}"  "${1}"
    fi
    DONE=1
fi





# translate output from file
if [[ ! $DONE ]] && [ -f "${1}" ] && [[ $TERMOUT ]]
then
    newfile=
    ${TR} -d '\15\32' < "${1}"
    DONE=1
fi


# make separate translated file from a file
if [[ ! $DONE ]] && [ -f "${1}" ] && [ -f "${2}" ]
then
    newfile="${TEMPDIR}/tr.temp"
    ${TR} -d '\15\32' < "${1}" > "${newfile}"

    if [ -e "${newfile}" ]; then
    check_overwrite "${2}"
    result=$?  #result of last function
    if [[ $result -eq 1 ]] ; then
        mv "${newfile}"  "${2}"
    else
        echo "creating file ${2}.d2u"
        mv "${newfile}"  "${2}.d2u"
    fi

    fi
    DONE=1
fi


#END