CoreUtil* structs to facilitate common behavior

common/common.v

@@ -4,6 +4,19 @@ import flag
 
 pub const version = '0.0.1'
 
+pub struct CoreutilInfo {
+pub:
+	name        string
+	description string
+}
+
+pub struct CoreutilExitDetail {
+	message string
+mut:
+	return_code      int = 1
+	show_help_advice bool // defaults to false
+}
+
 // coreutils_version returns formatted coreutils tool version
 pub fn coreutils_version() string {
 	return '(V coreutils) ${common.version}'
@@ -46,3 +59,28 @@ pub fn exit_with_error_message(tool_name string, error string) {
 	eprintln("Try '${tool_name} --help' for more information.")
 	exit(1)
 }
+
+// A common way to exit with a custom error code (default: 1)
+// and the ability to direct the user to help (default: false)
+// to make it easier to match the output of the GNU coreutils
+@[noreturn]
+pub fn (app CoreutilInfo) quit(detail CoreutilExitDetail) {
+	eprintln('${app.name}: ${detail.message}')
+	if detail.show_help_advice {
+		eprintln("Try '${app.name} --help' for more information.")
+	}
+	exit(detail.return_code)
+}
+
+// flag_parser returns a flag.FlagParser, with the common
+// options already set, reducing the boilerplate code in
+// each individual utility.
+pub fn (app CoreutilInfo) make_flag_parser(args []string) &flag.FlagParser {
+	mut fp := flag.new_flag_parser(args)
+	fp.version(coreutils_version())
+	fp.footer(coreutils_footer())
+	fp.skip_executable()
+	fp.application(app.name)
+	fp.description(app.description)
+	return fp
+}