1 files changed, 141 insertions, 0 deletions
diff --git a/tools/shld.sh b/tools/shld.sh
new file mode 100755
index 0000000..14335da
--- /dev/null
+++ b/tools/shld.sh
@@ -0,0 +1,141 @@
+#!/bin/sh
+#
+# Shell command language linker
+#
+# Copyright (C) 2015  Patrick "P. J." McDermott
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+set -u
+
+VERSION='0.1.0'
+
+output='out.sh'
+make_executable=true
+interpreter='/bin/sh'
+entry_point='main'
+
+die()
+{
+	local fmt="${1}"
+	shift 1
+
+	printf "shld: ${fmt}\n" "${@}"
+	exit 2
+}
+
+link()
+{
+	local input=
+
+	# Open output file.
+	if ! exec 3>"${output}~"; then
+		die 'Cannot open file "%s"' "${output}~"
+	fi
+
+	# Write magic number and interpreter path.
+	if ${make_executable}; then
+		printf '#!%s\n' "${interpreter}" >&3
+	fi
+
+	# Read input files.
+	for input in "${@}"; do
+		if ! cat "${input}" >&3; then
+			die 'Cannot read file "%s"' "${input}"
+		fi
+	done
+
+	# Add call to entry point.
+	if ${make_executable}; then
+		printf '\n%s "${@}"\n' "${entry_point}" >&3
+	fi
+
+	# Close output file, make it executable, and set its name.
+	exec 3>&-
+	if ${make_executable}; then
+		if ! chmod a+x "${output}~"; then
+			die 'Cannot set mode of file "%s"' "${output}~"
+		fi
+	fi
+	if ! mv "${output}~" "${output}"; then
+		die 'Cannot rename file to "%s"' "${output}"
+	fi
+}
+
+usage()
+{
+	printf 'Usage: %s [option ...] <file>...\n' "${0}"
+}
+
+help()
+{
+	usage
+	cat <<EOF
+Options:
+  -h           Display this information
+  -V           Display linker version information
+  -I <interp>  Use <interp> as the the interpreter for your program, instead of
+               the default of "/bin/sh"
+  -e <entry>   Use <entry> as the function for beginning execution of your
+               program, instead of the default of "main"
+  -o <output>  Use <output> as the name of the program produced by shld, instead
+               of the default of "out.sh"
+EOF
+}
+
+version()
+{
+	cat <<EOF
+shld ${VERSION}
+Copyright (C) 2015  Patrick "P. J." McDermott
+License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
+This is free software: you are free to change and redistribute it.
+There is NO WARRANTY, to the extent permitted by law.
+EOF
+}
+
+main()
+{
+	while getopts 'hVI:e:o:' opt; do
+		case "${opt}" in
+			'h')
+				help
+				exit
+				;;
+			'V')
+				version
+				exit
+				;;
+			'I')
+				interpreter="${OPTARG}"
+				;;
+			'e')
+				entry_point="${OPTARG}"
+				;;
+			'o')
+				output="${OPTARG}"
+				;;
+		esac
+	done
+	shift $(($OPTIND - 1))
+
+	if [ ${#} -lt 1 ]; then
+		usage >&2
+		exit 1
+	fi
+
+	link "${@}"
+}
+
+main "${@}"