read in bash on whitespace-delimited file without empty fields collapsing

Question

I\'m trying to read a multi-line tab-separated file in bash. The format is such that empty fields are expected. Unfortunately, the shell is collapsing together field separat

Answer 1

I've written a function which works around this issue. This particular implementation is particular about tab-separated columns and newline-separated rows, but that limitation could be removed as a straightforward exercise:

read_tdf_line() {
    local default_ifs=$' \t\n'
    local n line element at_end old_ifs
    old_ifs="${IFS:-${default_ifs}}"
    IFS=$'\n'

    if ! read -r line ; then
        return 1
    fi
    at_end=0
    while read -r element; do
        if (( $# > 1 )); then
            printf -v "$1" '%s' "$element"
            shift
        else
            if (( at_end )) ; then
                # replicate read behavior of assigning all excess content
                # to the last variable given on the command line
                printf -v "$1" '%s\t%s' "${!1}" "$element"
            else
                printf -v "$1" '%s' "$element"
                at_end=1
            fi
        fi
    done < <(tr '\t' '\n' <<<"$line")

    # if other arguments exist on the end of the line after all
    # input has been eaten, they need to be blanked
    if ! (( at_end )) ; then
        while (( $# )) ; do
            printf -v "$1" '%s' ''
            shift
        done
    fi

    # reset IFS to its original value (or the default, if it was
    # formerly unset)
    IFS="$old_ifs"
}

Usage as follows:

# read_tdf_line one two three rest <<<$'one\t\tthree\tfour\tfive'
# printf '<%s> ' "$one" "$two" "$three" "$rest"; printf '\n'
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