Re: reported nasty bash bug -- arithmetic problem, incorrect return code with ((var++)) when var is 0 before operation

26 Apr 2017

      Hi,

Below is the actual code that I am using FWIW, I don't claim it is
perfect, but it does the job of collecting the WinSCP files of a
release, as well as compiling checksum files from the release's readme file.

The format of the readme file has been constant for quite some time (if
not since it was first devised).  The files I want haven't changed either.

Of course it would be easier if they released proper md5sum, sha1sum and
sha256sum files so that I didn't need to construct them.

The download version is within the file name of the shell script.  I
could just as easily use the directory name to determine the version
though.  Basically I create a directory, copy in or hard link the file
from "last time", adjust it if necessary (name at least) and run it.

The script seems to be quite effective in getting all the files and
confirming they are valid according to the checksums provided in the readme.

I actually haven't used WinSCP itself for a while now as I only use
Windows for very few things these days (aside from when I am working on
other people's machines providing IT support services).

Cheers
A.

$ cat get-files--5.9.5.sh
#!/bin/bash

set -eu

get_files() {
    for TARGET_FILE in ${files_to_download}
    do
        while [ ! -f "${TARGET_FILE}" ]
        do
            FILE_URL="${URL_BASE}/download/${TARGET_FILE}"
            CURL_SAVE_FILE="${TARGET_FILE}--curl-ILs.out"
            curl -ILs "${FILE_URL}" | \
                tr -d "\r" | \
                tee "${CURL_SAVE_FILE}"
            FINAL_DOWNLOAD_URL=$(
                grep -i ^Location: "${CURL_SAVE_FILE}" | \
                    tail -1 | \
                    cut -d" " -f2
            )
            [[ -z "${FINAL_DOWNLOAD_URL}" ]] && \
                FINAL_DOWNLOAD_URL="${FILE_URL}"
            echo " -------------------------------------------"
            echo "          File URL: ${FILE_URL}"
            echo "Final Download URL: ${FINAL_DOWNLOAD_URL}"
            echo
            wget -c "${FINAL_DOWNLOAD_URL}"
            echo
        done
    done
    return 0
}

make_checksum_files() {
    declare -a files_with_checksums checksums
    files_with_checksums=(
        $(
            grep ^W "${README_FILE}" | tr -d "\r"
        )
    )
    for sum_type in MD5 SHA-1 SHA-256
    do
        checksums=(
            $(
                grep "${sum_type}" "${README_FILE}" | \
                    tr -d "\r" | \
                    cut -d" " -f4
            )
        )
        case "${sum_type}" in
            MD5)     OUT_FILE=md5sums    ;;
            SHA-1)   OUT_FILE=sha1sums   ;;
            SHA-256) OUT_FILE=sha256sums ;;
        esac
        for ((i=0;i<${#files_with_checksums[@]};i++))
        do
            printf "%s  %s\n" \
                "${checksums[${i}]}" \
                "${files_with_checksums[${i}]}"
        done | tee "${OUT_FILE}"
        touch -r "${README_FILE}" "${OUT_FILE}"
        echo
    done
    return 0
}

FN=$0
echo "${FN}"

# Strip prefix up to double dash
VER=${FN#*--}

URL_BASE=https://winscp.net/

# Strip suffix .sh
VER=${VER%%.sh}

files_to_download="
WinSCP-${VER}-Automation.zip
WinSCP-${VER}-Portable.zip
WinSCP-${VER}-ReadMe.txt
WinSCP-${VER}-Setup.exe
WinSCP-${VER}-Source.zip
"

(
echo
echo "WinSCP Website: ${URL_BASE}"
echo
echo "-- download version: $VER"
echo

get_files
echo " -------------------------------------------"

README_FILE=WinSCP-${VER}-ReadMe.txt
[ -f "${README_FILE}" ] || {
    echo Missing "${README_FILE}"
    exit
}

echo
cat "${README_FILE}"
echo
echo

make_checksum_files

echo
echo

for sum_file in md5sums sha1sums sha256sums
do
    [ -f "${sum_file}" ] || {
        echo missing "${sum_file}"
        exit
    }
    echo checking "${sum_file}" ....
    ${sum_file:0:(-1)} -c "${sum_file}"
    echo
done
echo

chown -R andrewm:andrewm .
ls -lart
) 2>&1 | tee "$(basename "$0")".out

Re: reported nasty bash bug -- arithmetic problem, incorrect return code with ((var++)) when var is 0 before operation

Andrew McGlashan