add tail command

clite/commands.js

@@ -1304,7 +1304,7 @@ head - copy the first part of files
 Usage: head [OPTION] <FILE>
 
 Options:
--n	the number of lines to print (default 10)
+-n N	the number of lines to print (default 10)
 -?	Print this help information
 		`);
 	}
@@ -1377,6 +1377,120 @@ Options:
 	return main(args);
 });
 
+clite.commands.load('tail',function(args,env,io) {
+	var stdio = io.include('stdio');
+	var clite = io.include('clite');
+	var lines = 10;
+	var chars = 0;
+
+	function help() {
+		stdio.printf(`
+tail - copy the last part of a file
+Usage: tail [OPTION] <FILE>
+
+Options:
+-n N	the number of lines to print (default 10)
+-c N	instead of lines, print the last N characters
+-?	Print this help information
+		`);
+	}
+
+	function writeFile(fd) {
+		if (!fd) {
+			stdio.fprintf(io.stderr,'could not open file\n');
+			io.exit(1);
+			return;
+		}
+
+		var d = stdio.readAll(fd);
+
+		if (chars > 0) {
+			if (d.length < chars) {
+				stdio.write(io.stdout,d);
+			}else{
+				stdio.write(io.stdout,d.substring(d.length-chars));
+			}
+		}else{
+			var ls = d.split('\n');
+			if (ls[ls.length-1] == '')
+				ls.pop();
+
+			while (ls.length > lines) {
+				ls.shift();
+			}
+
+			ls.forEach(function(l) {
+				stdio.printf('%s\n',l);
+			});
+		}
+
+		stdio.close(fd);
+		io.exit(0);
+	}
+
+	function main(args) {
+		var lnext = false;
+		var cnext = 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 'c':
+						cnext = true;
+						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 (cnext) {
+				chars = parseInt(args[i]);
+				if (chars < 1) {
+					stdio.fprintf(io.stderr,'invalid characters count "%d"\n',chars);
+					return 1;
+				}
+				cnext = 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');