Simplest method to convert file-size with suffix to bytes

Question

Title says it all really, but I'm currently using a simple function with a case statement to convert human-readable file size strings into a size in bytes. It works well enough, but it's a bit unwieldy for porting into other code, so I'm curious to know if there are any widely available commands that a shell script could use instead?

Basically I want to take strings such as "100g" or "100gb" and convert them into bytes.

I'm currently doing the following:

to_bytes() {
    value=$(echo "$1" | sed 's/[^0123456789].*$//g')
    units=$(echo "$1" | sed 's/^[0123456789]*//g' | tr '[:upper:]' '[:lower:]')

    case "$units" in
        t|tb)   let 'value *= 1024 * 1024 * 1024 * 1024'    ;;
        g|gb)   let 'value *= 1024 * 1024 * 1024'   ;;
        m|mb)   let 'value *= 1024 * 1024'  ;;
        k|kb)   let 'value *= 1024' ;;
        b|'')   let 'value += 0'    ;;
        *)
                value=
                echo "Unsupported units '$units'" >&2
        ;;
    esac

    echo "$value"
}

It seems a bit overkill for something I would have thought was fairly common for scripts working with files; common enough that something might exist to do this more quickly.

If there are no widely available solutions (i.e - majority of unix and linux flavours) then I'd still appreciate any tips for optimising the above function as I'd like to make it smaller and easier to re-use.

Answer 1

See man numfmt.

# numfmt --from=iec 42 512K 10M 7G 3.5T
42
524288
10485760
7516192768
3848290697216

# numfmt --to=iec 42 524288 10485760 7516192768 3848290697216
42
512K
10M
7.0G
3.5T