A script to update an executable that has been installed to GOBIN with "go install"

gofre.sh

#!/bin/sh -e

## This Source Code Form is subject to the terms of the Mozilla Public
## License, v. 2.0. If a copy of the MPL was not distributed with this
## file, You can obtain one at https://mozilla.org/MPL/2.0/.

self=$(basename "$0")
usage=$(cat) <<***
Usage:  $self [OPTIONS] COMMAND [VERSION]

Update an executable that has been installed to GOBIN with "go install".
The executable must have been compiled in module-aware mode.

   -n       make no changes, only display current version
  --help	display this help and exit

COMMAND is the file base name (without the GOBIN path) of the targetted
executable in the GOBIN directory, i.e. the name one would type to run
the command when GOBIN is in PATH.

Optional VERSION can be specified to install that specific version of
the COMMAND instead of the latest.

Example:
  $self wire v0.5.0
***

main() {
	noop=
	parseOpts "$@"
	shift $((OPTIND - 1))

	[ "$1" ] || die 1 'COMMAND argument required'

	: "${GOBIN:=${GOPATH:-$HOME/go}/bin}"
	export GOBIN="$GOBIN"

	version=${2:-latest}
	ex=$GOBIN/$(basename "$1")
	[ -e "$ex" ] || die 2 '%s not found in GOBIN' "$1"

	v=$(getVer "$ex")
	p=$(extractPath "$v")

	if [ ! "$noop" ]; then
		go install "${p}@${version}"

		m=$(extractMod "$v")
		goV="$(extractGoVer "$ex" "$v")"
		printCmdV was "$p" "$m" "$goV"

		v=$(getVer "$ex")
		p=$(extractPath "$v")
	fi

	m=$(extractMod "$v")
	goV="$(extractGoVer "$ex" "$v")"
	printCmdV now "$p" "$m" "$goV"
}

parseOpts() { ## ($@)
	while getopts :-:n OPT "$@"; do
		case $OPT in
		n) noop=1 ;;
		-) case "$OPTARG" in
			help) die ;;
			*) die 1 'unrecognized option: --%s' "$OPTARG" ;;
			esac ;;
		?) die 1 'unrecognized short option: -%s' "$OPTARG" ;;
		esac
	done
}
die() { ## (code [msgFormat [msgParams...]])
	c=${1:-0}
	if [ "$2" ]; then
		f=$2\\n
		shift 2
		eprintf "$f" "$@"
	fi
	printf %s\\n "$usage"
	exit "$c"
}
getVer() { ## (executablePath)
	ex=$1 c="go version -m" v=$($c "$ex")
	[ "$v" ] || exit 2
	if [ "${v##"$ex: go"*}" ]; then
		eprintf 'unrecognized output from "%s"' "$c"
		return 3
	fi
	printf %s "$v"
}
extractGoVer() { ## (executablePath goVersionOutput)
	extract 'Go compiler version' "${2#"$1"}" ': (go\S+)' '\1'
}
extractPath() { ## (goVersionOutput)
	subExtract 'command path' "$1" path || return 4
}
extractMod() { ## (goVersionOutput)
	subExtract 'version info' "$1" mod '\s+(\S+)\s+.*' '@\2' || return 5
}
printCmdV() { ## (prefix cmdPath module@version goVersion)
	printf '%s:\t%s@%s\t%s\n' "$1" "$2" "${3#*@}" "$4"
}

subExtract() { ## (desc data prefix [patternSuffix [substitutionSuffix]])
	extract "$1" "$2" '[\t ]+'"$3"'\s+(\S+)'"$4" '\1'"$5"
}
extract() ( ## (desc data pattern substitution)
	v=$(printf %s "$2" | sed -E "s/^$3$/$4/;t;d")
	if [ ! "$v" ]; then
		eprintf 'failed extracting %s from the "go version -m" output:\n%s\n' \
			"$1" "$2"
		return 1
	fi
	printf %s "$v"
)
eprintf() { ## (format [parameters...])
	f="$self: $1"
	shift
	# shellcheck disable=SC2059
	printf "$f" "$@" >&2
}

main "$@"