add head function

clite/commands.js

@@ -1293,6 +1293,90 @@ Options:
 	return main(args);
 });
 
+clite.commands.load('head',function(args,env,io) {
+	var stdio = io.include('stdio');
+	var clite = io.include('clite');
+	var lines = 10;
+
+	function help() {
+		stdio.printf(`
+head - copy the first part of files
+Usage: head [OPTION] <FILE>
+
+Options:
+-n	the number of lines to print (default 10)
+-?	Print this help information
+		`);
+	}
+
+	function writeFile(fd) {
+		if (!fd) {
+			stdio.fprintf(io.stderr,'could not open file\n');
+			io.exit(1);
+			return;
+		}
+
+		var l;
+		for (var i=0; i<lines && (l = stdio.readLine(fd)) != null; i++) {
+			stdio.printf('%s\n',l);
+		}
+
+		stdio.close(fd);
+		io.exit(0);
+	}
+
+	function main(args) {
+		var lnext = false;
+		var short = null;
+		var file = null;
+		for (var i=1; i<args.length; i++) {
+			if (args[i][0] == '-') {
+				for (var j=1; j<args[i].length; j++) {
+					switch (args[i][j]) {
+					case '?':
+						help();
+						return 0;
+						break;
+					case 'n':
+						lnext = true;
+						break;
+					default:
+						stdio.fprintf(io.stderr,'unknown argument: -%c\n',args[i][j]);
+					}
+				}
+			}else if (lnext) {
+				lines = parseInt(args[i]);
+				if (lines < 1) {
+					stdio.fprintf(io.stderr,'invalid lines count "%d"\n',lines);
+					return 1;
+				}
+				lnext = false;
+			}else if (file == null) {
+				short = args[i];
+				file = clite.resolvePath(args[i]);
+			}else{
+				stdio.fprintf(io.stderr,'unknown argument: %s\n',args[i]);
+			}
+		}
+
+		if (file == null) {
+			stdio.write(io.stderr,'no file specified\n');
+			return 1;
+		}
+
+		var fd = stdio.open(file,stdio.flags.O_RDONLY,writeFile);
+		if (!fd) {
+			stdio.fprintf(io.stderr,'could not open file: %s\n',short);
+			return 1;
+		}
+
+		return null;
+	}
+
+
+	return main(args);
+});
+
 if (window.location.protocol == 'file:')
 clite.commands.load('test',function(args,env,io) {
 	var stdio = io.include('stdio');