A script to update shellcheck when using the precompiled binary

upgrade_shellcheck

#!/bin/bash

# A quick script to automate upgrading the shellcheck binary

# Terse assign our default proxy settings if required
#: "${http_proxy:=http://proxy.company.org:3128}"
#: "${https_proxy:=$http_proxy}"

trap "rm -rf /tmp/shellcheck-latest*" EXIT

die() {
  tput setaf 1
  printf '%s\n' "$@" >&2
  tput sgr0
  exit 1
}

# Function to convert a semantic version number to an integer
# This zero-pads the second and third number, just in case
# either of those numbers goes into double digits
# This allows comparisons between e.g. 2.5.5 and 2.10.1 (i.e. 20505 < 21001)
sem_to_int() {
  awk -F '.' '{printf "%i%02i%02i" , $1, $2, $3 }'
}

# If an existing version is in PATH, get its version and path
if command -v shellcheck >/dev/null 2>&1; then
  curVersion=$(shellcheck -V | awk -F ': ' '/^version/{print $2}')
  curVersionInt=$(sem_to_int <<< "${curVersion}")
  # The following isn't used, the idea is to potentially deal with install paths
  # that aren't /usr/bin e.g. /usr/local/bin or /bin or anything really...
  # In this case, we're expecting /usr/bin for a quick script,
  # so we don't need to build this extra logic and handling
  #curLocation=$(command -v shellcheck)
fi

# Open a subshell to contain our filesystem moves
(
  cd /tmp || die "[ERROR]: Could not cd into '/tmp'"

  # Remove any existing copy (i.e. prior download) of the latest binary
  rm -f shellcheck-latest.linux.x86_64.tar.xz 2>/dev/null

  # Grab the latest version
  wget https://shellcheck.storage.googleapis.com/shellcheck-latest.linux.x86_64.tar.xz ||
    die "[ERROR]: Unable to download latest tar.xz file, please investigate"

  # Extract it
  tar -xf shellcheck-latest.linux.x86_64.tar.xz

  cd shellcheck-latest || die "[ERROR]: Could not cd into './shellcheck-latest'"

  # Get the latest version
  newVersion=$(./shellcheck -V | awk -F ': ' '/^version/{print $2}')
  newVersionInt=$(sem_to_int <<< "${newVersion}")

  # If there is a current version, compare and act
  if (( newVersionInt == curVersionInt )); then
    printf -- '%s\n' "Latest version (${curVersion}) already installed, exiting..."
    exit 0
  elif (( newVersionInt > curVersionInt )); then
    printf -- '%s\n' "Older version (${curVersion}) found, upgrading to ${newVersion}..."

    printf -- '%s\n' "Copying /usr/bin/shellcheck to /usr/bin/shellcheck.${curVersion}"
    cp /usr/bin/shellcheck /usr/bin/shellcheck."${curVersion}"

    printf -- '%s\n' "Copying shellcheck (${curVersion}) to /usr/bin/shellcheck"
    install -o root -g root -m 755 shellcheck /usr/bin

    printf -- '%s\n' "Upgrade complete"
    exit 0
  # Otherwise, just copy the binary into /usr/bin
  else
    install -o root -g root -m 755 shellcheck /usr/bin
  fi
)