gb

#!/bin/bash

function writeLog() {
    echo "$(date +'%Y-%m-%d %H:%M:%S%z') $*"
}

# ${var%regex}: Delete everything after shortest match of regex
# ${var##regex}: Delete everything before longest match of regex
# ${var:-expr}: Use ${var} or 'expr' if $var is empty or not set
function getExecutableName {
   executableName="${PWD%"${PWD##*[!/]}"}" # Get all trailing '/' and remove them
   executableName="${executableName##*/}"  # Remove everything up to last / leaving only the last part after the last /
   executableName="${executableName:-/}"   # If the executable name is empty set it to '/'
}

function buildExecutable() {
   writeLog "Start build for ${GOOS}/${GOARCH}"

   realExecutableName=${executableName}
   # ${var,,}: Convert value of 'var' to lower case
   if [ "${GOOS,,}" == "windows" ]; then
      realExecutableName="${realExecutableName}.exe"
   fi

   # -s: Omit the symbol table and debug information
   # -w: Omit the DWARF symbol table
   # -trimpath: Remove all file system paths from the resulting executable
   go build -ldflags="-s -w" -trimpath
   rc=$?
   writeLog "Go build for ${GOOS}/${GOARCH} has error level ${rc}"

   if [ ${rc} -eq 0 ]; then
      if [ ${useCompression} -ne 0 ]; then
         ${upxPath} --best --lzma -v "${realExecutableName}"
      fi

      writeLog "Built ${GOOS}/${GOARCH} executable ${realExecutableName}"
   fi
}

thisProc="${0%"${0##*[!/]}"}" # extglob-free multi-trailing-/ trim
thisProc="${thisProc##*/}"  # remove everything before the last /

writeLog "Start ${thisProc}"

# Constants
upxPath="${HOME}/upx/upx"
export CGO_ENABLED=0
export GOARCH=amd64
export GOAMD64=v2

# Check parameter
useCompression=0
# ${var:+expr}: If var is empty or not set return an empty string, if it is set return 'expr'
# This ensures a consistent value to check if $1 is set to any value
if [ -n "${1:+x}" ]; then
   if [ -f "${upxPath}" ]; then
      useCompression=1
   else
      writeLog "UPX does not exist at ${upxPath}"
   fi
fi

getExecutableName

echo ""
export GOOS=windows
buildExecutable
echo ""

export GOOS=linux
buildExecutable
echo ""

writeLog "End ${thisProc}"