build: improve help.

This commit corrects linelength (this should have no functional impact)
and adds exit codes (sysexit.sh)

Signed-off-by: Denis 'GNUtoo' Carikli <GNUtoo@cyberdimension.org>
Acked-by: Adrien 'neox' Bourmault <neox@gnu.org>
neox: wrote the commit message

build

@@ -27,6 +27,8 @@ set -u -e
 
 projectname="$(cat projectname)"
 
+. resources/scripts/misc/sysexits.sh
+
 # This is for backward compatibility: before the list of "modes" was
 # auto-detected, but there isn't a 1:1 matching between modes and
 # packages tasks (build, clean, etc).
@@ -67,7 +69,9 @@ list_packages() {
 
 help() {
 	cat <<- EOF
-	USAGE:	./build <TASK> <PACKAGE>
+	Usage:
+	        ./build <TASK> <PACKAGE>
+	        ./build --help
 
 	possible values for 'task':
 	$(list_tasks)
@@ -82,12 +86,16 @@ help() {
 }
 
 die() {
+	ret="$1"
+	shift 1
+
 	printf 'Error: %s\n' "${@}" 1>&2
-	exit 1
+	exit "${ret}"
 }
 
 if [ $# -lt 1 ]; then
-	die "Wrong number of arguments specified. See './build help'."
+    die "${EX_USAGE}" \
+	"Wrong number of arguments specified. See './build --help'."
 fi
 
 task="${1}"
@@ -96,7 +104,7 @@ if [ "${task}" != "dependencies" ]; then
 	./resources/scripts/misc/versioncheck
 fi
 
-[ "${task}" = help ] && help && exit 0
+[ "${task}" = "--help" ] && help && exit 0
 
 if [ $# -gt 1 ]; then
 
@@ -107,8 +115,9 @@ if [ $# -gt 1 ]; then
 		list)
 			tasks_paths=$(list_tasks_paths "${task}")
 			if [ -z "${tasks_paths}" ] ; then
-				die "Invalid task '${task}'." \
+				die "${EX_USAGE}" \
-				    " See './build help'."
+				    "Invalid task '${task}'." \
+				    " See './build --help'."
 			else
 				printf "Available packages for task '%s':\n\n" \
 				   "${task}"
@@ -127,13 +136,15 @@ if [ $# -gt 1 ]; then
 					"${pkg_dir}"/"${task}" $@
 				else
 					help
-					die "Invalid package for '${task}'." \
+					die "${EX_USAGE}" \
+					    "Invalid package for '${task}'." \
 					    " See './build ${task} list'."
 				fi
 			else
 				help
-				die "Invalid task '${task}'." \
+				die "${EX_USAGE}" \
-				    " See './build help'."
+				    "Invalid task '${task}'." \
+				    " See './build --help'."
 			fi
 	esac
 else

resources/scripts/misc/sysexits.sh

@@ -0,0 +1,104 @@
+# Copyright (c) 1987, 1993
+#	The Regents of the University of California.  All rights reserved.
+# Copyright (c) 2023 Denis 'GNUtoo' Carikli <GNUtoo@cyberdimension.org>
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in the
+#    documentation and/or other materials provided with the distribution.
+# 4. Neither the name of the University nor the names of its contributors
+#    may be used to endorse or promote products derived from this software
+#    without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+# SUCH DAMAGE.
+#
+#	@(#)sysexits.h	8.1 (Berkeley) 6/2/93
+#	@(#)sysexits.sh 8.1 (GNUtoo) 27 November 2023: Adapted from sysexits.h
+
+#  sysexits.sh -- Exit status codes for system programs.
+#
+#	This include file attempts to categorize possible error
+#	exit statuses for system programs, notably delivermail
+#	and the Berkeley network.
+#
+#	Error numbers begin at EX__BASE to reduce the possibility of
+#	clashing with other exit statuses that random programs may
+#	already return.  The meaning of the codes is approximately
+#	as follows:
+#
+#	EX_USAGE -- The command was used incorrectly, e.g., with
+#		the wrong number of arguments, a bad flag, a bad
+#		syntax in a parameter, or whatever.
+#	EX_DATAERR -- The input data was incorrect in some way.
+#		This should only be used for user's data & not
+#		system files.
+#	EX_NOINPUT -- An input file (not a system file) did not
+#		exist or was not readable.  This could also include
+#		errors like "No message" to a mailer (if it cared
+#		to catch it).
+#	EX_NOUSER -- The user specified did not exist.  This might
+#		be used for mail addresses or remote logins.
+#	EX_NOHOST -- The host specified did not exist.  This is used
+#		in mail addresses or network requests.
+#	EX_UNAVAILABLE -- A service is unavailable.  This can occur
+#		if a support program or file does not exist.  This
+#		can also be used as a catchall message when something
+#		you wanted to do doesn't work, but you don't know
+#		why.
+#	EX_SOFTWARE -- An internal software error has been detected.
+#		This should be limited to non-operating system related
+#		errors as possible.
+#	EX_OSERR -- An operating system error has been detected.
+#		This is intended to be used for such things as "cannot
+#		fork", "cannot create pipe", or the like.  It includes
+#		things like getuid returning a user that does not
+#		exist in the passwd file.
+#	EX_OSFILE -- Some system file (e.g., /etc/passwd, /etc/utmp,
+#		etc.) does not exist, cannot be opened, or has some
+#		sort of error (e.g., syntax error).
+#	EX_CANTCREAT -- A (user specified) output file cannot be
+#		created.
+#	EX_IOERR -- An error occurred while doing I/O on some file.
+#	EX_TEMPFAIL -- temporary failure, indicating something that
+#		is not really an error.  In sendmail, this means
+#		that a mailer (e.g.) could not create a connection,
+#		and the request should be reattempted later.
+#	EX_PROTOCOL -- the remote system returned something that
+#		was "not possible" during a protocol exchange.
+#	EX_NOPERM -- You did not have sufficient permission to
+#		perform the operation.  This is not intended for
+#		file system problems, which should use NOINPUT or
+#		CANTCREAT, but rather for higher level permissions.
+
+EX_OK=0           # successful termination
+EX__BASE=64       # base value for error messages
+EX_USAGE=64       # command line usage error
+EX_DATAERR=65     # data format error
+EX_NOINPUT=66     # cannot open input
+EX_NOUSER=67      # addressee unknown
+EX_NOHOST=68      # host name unknown
+EX_UNAVAILABLE=69 # service unavailable
+EX_SOFTWARE=70    # internal software error
+EX_OSERR=71       # system error (e.g., can't fork)
+EX_OSFILE=72      # critical OS file missing
+EX_CANTCREAT=73   # can't create (user) output file
+EX_IOERR=74       # input/output error
+EX_TEMPFAIL=75    # temp failure; user is invited to retry
+EX_PROTOCOL=76    # remote error in protocol
+EX_NOPERM=77      # permission denied
+EX_CONFIG=78      # configuration error
+EX__MAX=78        # maximum listed value