From 56cc5da9fb86ff4e610732b62934b131650f86a4 Mon Sep 17 00:00:00 2001
From: Bananymous <oskari.alaranta@bananymous.com>
Date: Thu, 5 Dec 2024 08:14:45 +0200
Subject: [PATCH] userspace: Implement `ln` utility

---
 userspace/programs/CMakeLists.txt    |  1 +
 userspace/programs/ln/CMakeLists.txt |  8 ++++
 userspace/programs/ln/main.cpp       | 65 ++++++++++++++++++++++++++++
 3 files changed, 74 insertions(+)
 create mode 100644 userspace/programs/ln/CMakeLists.txt
 create mode 100644 userspace/programs/ln/main.cpp

diff --git a/userspace/programs/CMakeLists.txt b/userspace/programs/CMakeLists.txt
index 6e49c53f..dabff242 100644
--- a/userspace/programs/CMakeLists.txt
+++ b/userspace/programs/CMakeLists.txt
@@ -14,6 +14,7 @@ set(USERSPACE_PROGRAMS
 	id
 	image
 	init
+	ln
 	loadfont
 	loadkeys
 	ls
diff --git a/userspace/programs/ln/CMakeLists.txt b/userspace/programs/ln/CMakeLists.txt
new file mode 100644
index 00000000..496e74ef
--- /dev/null
+++ b/userspace/programs/ln/CMakeLists.txt
@@ -0,0 +1,8 @@
+set(SOURCES
+	main.cpp
+)
+
+add_executable(ln ${SOURCES})
+banan_link_library(ln libc)
+
+install(TARGETS ln OPTIONAL)
diff --git a/userspace/programs/ln/main.cpp b/userspace/programs/ln/main.cpp
new file mode 100644
index 00000000..11e7647f
--- /dev/null
+++ b/userspace/programs/ln/main.cpp
@@ -0,0 +1,65 @@
+#include <libgen.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+int usage(const char* argv0, int ret)
+{
+	FILE* fout = ret ? stderr : stdout;
+	fprintf(fout, "usage: %s [OPTION]... TARGET [LINK_NAME]\n", argv0);
+	fprintf(fout, "  -s, --symbolic   create symbolic link instead of hard link\n");
+	fprintf(fout, "  -h, --help       show this message and exit\n");
+	return ret;
+}
+
+int main(int argc, const char* argv[])
+{
+	bool do_symlink = false;
+
+	int i = 1;
+	for (; i < argc; i++)
+	{
+		if (argv[i][0] != '-')
+			break;
+
+		if (strcmp(argv[i], "-s") == 0 || strcmp(argv[i], "--symbolic") == 0)
+			do_symlink = true;
+		else if (strcmp(argv[i], "-h") == 0 || strcmp(argv[i], "--help") == 0)
+			return usage(argv[0], 0);
+		else
+		{
+			fprintf(stderr, "unrecognized option '%s'\n", argv[i]);
+			return usage(argv[0], 1);
+		}
+	}
+
+	if (i == argc)
+	{
+		fprintf(stderr, "missing target\n");
+		return usage(argv[0], 1);
+	}
+
+	const char* target = argv[i++];
+
+	struct stat st;
+	if (stat(target, &st) == -1)
+	{
+		perror("stat");
+		return 1;
+	}
+
+	const char* link_name = (i == argc)
+		? basename(const_cast<char*>(target))
+		: argv[i];
+
+	int (*link_func)(const char*, const char*) = do_symlink ? &symlink : &link;
+
+	if (link_func(target, link_name) == -1)
+	{
+		perror(do_symlink ? "symlink" : "link");
+		return 1;
+	}
+
+	return 0;
+}