Add echo

Makefile

@@ -1,4 +1,4 @@
-APPS=init hello sh ls terminal uname compositor drawlines background session kdebug cat yutani-test sysinfo hostname yutani-query env mount date
+APPS=init hello sh ls terminal uname compositor drawlines background session kdebug cat yutani-test sysinfo hostname yutani-query env mount date echo
 
 CC=i686-pc-toaru-gcc
 AR=i686-pc-toaru-ar

echo.c

@@ -0,0 +1,73 @@
+/* This file is part of ToaruOS and is released under the terms
+ * of the NCSA / University of Illinois License - see LICENSE.md
+ * Copyright (C) 2013-2014 Kevin Lange
+ */
+/* vim: tabstop=4 shiftwidth=4 noexpandtab
+ *
+ * echo
+ *
+ * Prints its arguments (with some processing, ask --help)
+ * to standard out.
+ */
+#include <stdio.h>
+#include <string.h>
+
+void usage() {
+	printf("echo [-n] [-e] [STRING]...\n"
+	       "  -n    do not output a new line at the end\n"
+	       "  -e    process escape sequences\n");
+}
+
+int main(int argc, char ** argv) {
+	int start           = 1;
+	int use_newline     = 1;
+	int process_escapes = 0;
+
+	for (int i = start; i < argc; ++i) {
+		if (argv[i][0] != '-') {
+			start = i;
+			break;
+		} else {
+			if (argv[i][1] == 'h') {
+				usage();
+				return 1;
+			} else if (argv[i][1] == 'n') {
+				use_newline = 0;
+			} else if (argv[i][1] == 'e') {
+				process_escapes = 1;
+			}
+		}
+	}
+
+	for (int i = start; i < argc; ++i) {
+		if (process_escapes) {
+			for (int j = 0; j < strlen(argv[i]) - 1; ++j) {
+				if (argv[i][j] == '\\') {
+					if (argv[i][j+1] == 'e') {
+						argv[i][j] = '\033';
+						for (int k = j + 1; k < strlen(argv[i]); ++k) {
+							argv[i][k] = argv[i][k+1];
+						}
+					}
+					if (argv[i][j+1] == 'n') {
+						argv[i][j] = '\n';
+						for (int k = j + 1; k < strlen(argv[i]); ++k) {
+							argv[i][k] = argv[i][k+1];
+						}
+					}
+				}
+			}
+		}
+		printf("%s",argv[i]);
+		if (i != argc - 1) {
+			printf(" ");
+		}
+	}
+
+	if (use_newline) {
+		printf("\n");
+	}
+
+	fflush(stdout);
+	return 0;
+}