userspace: Implement `dirname` utility

This implementation now passes every musl-libc test :)

userspace/aoc2024/CMakeLists.txt

@@ -2,6 +2,8 @@ set(AOC2024_PROJECTS
 	day1
 	day2
 	day3
+	day4
+	day5
 	full
 )
 

userspace/aoc2024/day4/CMakeLists.txt

@@ -0,0 +1,9 @@
+set(SOURCES
+	main.cpp
+)
+
+add_executable(aoc2024_day4 ${SOURCES})
+banan_include_headers(aoc2024_day4 ban)
+banan_link_library(aoc2024_day4 libc)
+
+install(TARGETS aoc2024_day4 OPTIONAL)

userspace/aoc2024/day4/main.cpp

@@ -0,0 +1,132 @@
+#include <BAN/StringView.h>
+#include <BAN/Vector.h>
+
+#include <inttypes.h>
+#include <stdio.h>
+#include <string.h>
+
+using i8  = int8_t;
+using i16 = int16_t;
+using i32 = int32_t;
+using i64 = int64_t;
+
+using u8  = uint8_t;
+using u16 = uint16_t;
+using u32 = uint32_t;
+using u64 = uint64_t;
+
+struct Grid2D
+{
+	size_t width { 0 };
+	size_t height { 0 };
+	BAN::Vector<char> data;
+};
+
+static Grid2D read_grid2d(FILE* fp)
+{
+	size_t width { 0 };
+	size_t height { 0 };
+	BAN::Vector<char> data;
+
+	char buffer[1024];
+	while (fgets(buffer, sizeof(buffer), fp))
+	{
+		const size_t len = strlen(buffer);
+		if (len == 0 || buffer[0] == '\n')
+			break;
+		if (data.empty())
+			width = len - 1;
+		height++;
+
+		ASSERT(buffer[width] == '\n');
+
+		if (data.capacity() < height * width)
+			MUST(data.reserve(2 * height * width));
+
+		MUST(data.resize(height * width));
+		memcpy(&data[(height - 1) * width], buffer, width);
+	}
+
+	(void)data.shrink_to_fit();
+
+	return Grid2D {
+		.width = width,
+		.height = height,
+		.data = BAN::move(data),
+	};
+}
+
+static bool check_match(const Grid2D& puzzle, size_t x, size_t y, i32 step_x, i32 step_y, BAN::StringView target)
+{
+	if (i32 ex = (i32)x + step_x * (i32)(target.size() - 1); ex < 0 || ex >= (i32)puzzle.width)
+		return false;
+	if (i32 ey = (i32)y + step_y * (i32)(target.size() - 1); ey < 0 || ey >= (i32)puzzle.height)
+		return false;
+	for (size_t i = 0; i < target.size(); i++)
+		if (target[i] != puzzle.data[(y + i * step_y) * puzzle.width + (x + i * step_x)])
+			return false;
+	return true;
+}
+
+i64 part1(FILE* fp)
+{
+	i64 result = 0;
+
+	auto puzzle = read_grid2d(fp);
+	for (size_t y = 0; y < puzzle.height; y++) {
+		for (size_t x = 0; x < puzzle.width; x++) {
+			result += check_match(puzzle, x, y, 1,  0, "XMAS"_sv);
+			result += check_match(puzzle, x, y, 0,  1, "XMAS"_sv);
+			result += check_match(puzzle, x, y, 1,  1, "XMAS"_sv);
+			result += check_match(puzzle, x, y, 1, -1, "XMAS"_sv);
+
+			result += check_match(puzzle, x, y, 1,  0, "SAMX"_sv);
+			result += check_match(puzzle, x, y, 0,  1, "SAMX"_sv);
+			result += check_match(puzzle, x, y, 1,  1, "SAMX"_sv);
+			result += check_match(puzzle, x, y, 1, -1, "SAMX"_sv);
+		}
+	}
+
+	return result;
+}
+
+i64 part2(FILE* fp)
+{
+	i64 result = 0;
+
+	auto puzzle = read_grid2d(fp);
+	for (size_t y = 1; y < puzzle.height - 1; y++) {
+		for (size_t x = 1; x < puzzle.width - 1; x++) {
+			if (!check_match(puzzle, x - 1, y - 1, 1,  1, "MAS") && !check_match(puzzle, x - 1, y - 1, 1,  1, "SAM"))
+				continue;
+			if (!check_match(puzzle, x - 1, y + 1, 1, -1, "MAS") && !check_match(puzzle, x - 1, y + 1, 1, -1, "SAM"))
+				continue;
+			result++;
+		}
+	}
+
+	return result;
+}
+
+int main(int argc, char** argv)
+{
+	const char* file_path = "/usr/share/aoc2024/day4_input.txt";
+
+	if (argc >= 2)
+		file_path = argv[1];
+
+	FILE* fp = fopen(file_path, "r");
+	if (fp == nullptr)
+	{
+		perror("fopen");
+		return 1;
+	}
+
+	printf("part1: %" PRId64 "\n", part1(fp));
+
+	fseek(fp, 0, SEEK_SET);
+
+	printf("part2: %" PRId64 "\n", part2(fp));
+
+	fclose(fp);
+}

userspace/aoc2024/day5/CMakeLists.txt

@@ -0,0 +1,9 @@
+set(SOURCES
+	main.cpp
+)
+
+add_executable(aoc2024_day5 ${SOURCES})
+banan_include_headers(aoc2024_day5 ban)
+banan_link_library(aoc2024_day5 libc)
+
+install(TARGETS aoc2024_day5 OPTIONAL)

userspace/aoc2024/day5/main.cpp

@@ -0,0 +1,109 @@
+#include <BAN/Array.h>
+#include <BAN/Vector.h>
+#include <BAN/StringView.h>
+
+#include <ctype.h>
+#include <inttypes.h>
+#include <stdio.h>
+
+using i8  = int8_t;
+using i16 = int16_t;
+using i32 = int32_t;
+using i64 = int64_t;
+
+using u8  = uint8_t;
+using u16 = uint16_t;
+using u32 = uint32_t;
+using u64 = uint64_t;
+
+i64 part1(FILE* fp)
+{
+	bool requirements[100][100] {};
+	char buffer[128];
+
+	int a, b;
+	while (fgets(buffer, sizeof(buffer), fp) && sscanf(buffer, "%d|%d", &a, &b) == 2)
+		requirements[b][a] = true;
+
+	i64 result = 0;
+
+	while (fgets(buffer, sizeof(buffer), fp))
+	{
+		BAN::Vector<int> update;
+		for (size_t i = 0; isdigit(buffer[i]); i += 3)
+			MUST(update.push_back(atoi(&buffer[i])));
+
+		bool valid = true;
+		for (size_t i = 0; i < update.size() && valid; i++)
+			for (size_t j = i + 1; j < update.size() && valid; j++)
+				if (requirements[update[i]][update[j]])
+					valid = false;
+
+		if (valid)
+			result += update[update.size() / 2];
+	}
+
+	return result;
+}
+
+i64 part2(FILE* fp)
+{
+	bool requirements[100][100] {};
+	char buffer[128];
+
+	int a, b;
+	while (fgets(buffer, sizeof(buffer), fp) && sscanf(buffer, "%d|%d", &a, &b) == 2)
+		requirements[b][a] = true;
+
+	i64 result = 0;
+
+	while (fgets(buffer, sizeof(buffer), fp))
+	{
+		BAN::Vector<int> update;
+		for (size_t i = 0; isdigit(buffer[i]); i += 3)
+			MUST(update.push_back(atoi(&buffer[i])));
+
+		bool correct { true };
+		for (size_t i = 0; i < update.size(); i++)
+		{
+			for (size_t j = i + 1; j < update.size(); j++)
+			{
+				if (requirements[update[i]][update[j]])
+				{
+					BAN::swap(update[i], update[j]);
+					correct = false;
+					i--;
+					break;
+				}
+			}
+		}
+
+		if (!correct)
+			result += update[update.size() / 2];
+	}
+
+	return result;
+}
+
+int main(int argc, char** argv)
+{
+	const char* file_path = "/usr/share/aoc2024/day5_input.txt";
+
+	if (argc >= 2)
+		file_path = argv[1];
+
+	FILE* fp = fopen(file_path, "r");
+	if (fp == nullptr)
+	{
+		perror("fopen");
+		return 1;
+	}
+
+	printf("part1: %" PRId64 "\n", part1(fp));
+
+	fseek(fp, 0, SEEK_SET);
+
+	printf("part2: %" PRId64 "\n", part2(fp));
+
+	fclose(fp);
+}

userspace/libraries/LibC/stdio.cpp

@@ -529,11 +529,8 @@ int pclose(FILE* file)
 		return -1;
 	}
 
-	pid_t pid = file->pid;
-	(void)fclose(file);
-
 	int stat;
-	while (waitpid(pid, &stat, 0) != -1)
+	while (waitpid(file->pid, &stat, 0) == -1)
 	{
 		if (errno != EINTR)
 		{
@@ -541,6 +538,8 @@ int pclose(FILE* file)
 			break;
 		}
 	}
+
+	(void)fclose(file);
 	return stat;
 }
 

userspace/libraries/LibC/time.cpp

@@ -2,6 +2,7 @@
 #include <BAN/Math.h>
 
 #include <ctype.h>
+#include <errno.h>
 #include <string.h>
 #include <sys/syscall.h>
 #include <time.h>
@@ -64,11 +65,8 @@ char* ctime(const time_t* clock)
 	return ctime_r(clock, buf);
 }
 
-struct tm* gmtime_r(const time_t* timer, struct tm* __restrict result)
+static constexpr bool is_leap_year(uint64_t year)
 {
-	constexpr auto is_leap_year =
-		[](time_t year) -> bool
-		{
 	if (year % 400 == 0)
 		return true;
 	if (year % 100 == 0)
@@ -76,8 +74,63 @@ struct tm* gmtime_r(const time_t* timer, struct tm* __restrict result)
 	if (year % 4 == 0)
 		return true;
 	return false;
-		};
+}
 
+time_t mktime(struct tm* tm)
+{
+	if (tm->tm_year < 70)
+	{
+		errno = EOVERFLOW;
+		return -1;
+	}
+
+	tm->tm_min += tm->tm_sec / 60;
+	tm->tm_sec %= 60;
+
+	tm->tm_hour += tm->tm_min / 60;
+	tm->tm_min %= 60;
+
+	tm->tm_mday += tm->tm_hour / 24;
+	tm->tm_hour %= 24;
+
+	static constexpr int month_days[] { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
+
+	for (;;)
+	{
+		int days_in_month = month_days[tm->tm_mon];
+		if (tm->tm_mon == 1 && is_leap_year(tm->tm_year))
+			days_in_month++;
+
+		if (tm->tm_mday <= days_in_month)
+			break;
+
+		tm->tm_mday -= days_in_month;
+		tm->tm_mon++;
+	}
+
+	tm->tm_year += tm->tm_mon / 12;
+	tm->tm_mon %= 12;
+
+	tm->tm_yday = tm->tm_mday - 1;
+	if (tm->tm_mon > 0)
+		tm->tm_yday += month_days[tm->tm_mon - 1];
+
+	const time_t num_febs = (tm->tm_mon > 1) ? tm->tm_year + 1 : tm->tm_year;
+	const time_t leap_years = (num_febs - 69) / 4 - (num_febs - 1) / 100 + (num_febs + 299) / 400;
+
+	const time_t years = tm->tm_year - 70;
+	const time_t days = years * 365 + leap_years + tm->tm_yday;
+	const time_t hours = days * 24 + tm->tm_hour;
+	const time_t minutes = hours * 60 + tm->tm_min;
+	const time_t seconds = minutes * 60 + tm->tm_sec;
+
+	tm->tm_wday = (days + 4) % 7;
+
+	return seconds;
+}
+
+struct tm* gmtime_r(const time_t* timer, struct tm* __restrict result)
+{
 	constexpr uint64_t month_days[] { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 };
 
 	time_t time = *timer;
@@ -134,7 +187,7 @@ size_t strftime(char* __restrict s, size_t maxsize, const char* __restrict forma
 
 	struct conversion_t
 	{
-		char flag = '\0';
+		int flag = '\0';
 		int width = -1;
 		char modifier = '\0';
 	};
@@ -154,9 +207,9 @@ size_t strftime(char* __restrict s, size_t maxsize, const char* __restrict forma
 	};
 
 	const auto append_string =
-		[&](const char* string) -> bool
+		[&s, &len, &maxsize](const char* string) -> bool
 		{
-			size_t string_len = strlen(string);
+			const size_t string_len = strlen(string);
 			if (len + string_len >= maxsize)
 				return false;
 			strcpy(s + len, string);
@@ -165,7 +218,7 @@ size_t strftime(char* __restrict s, size_t maxsize, const char* __restrict forma
 		};
 
 	const auto append_string_from_list =
-		[&]<size_t LIST_SIZE>(int index, const char* const (&list)[LIST_SIZE]) -> bool
+		[&append_string]<size_t LIST_SIZE>(int index, const char* const (&list)[LIST_SIZE]) -> bool
 		{
 			const char* string = "INVALID";
 			if (index >= 0 && index < (int)LIST_SIZE)
@@ -174,15 +227,43 @@ size_t strftime(char* __restrict s, size_t maxsize, const char* __restrict forma
 		};
 
 	const auto append_value =
-		[&](const char* format, int value) -> bool
+		[&s, &len, &maxsize]<typename T>(const char* format, T value) -> bool
 		{
-			int written = snprintf(s + len, maxsize - len, format, value);
+			const int written = snprintf(s + len, maxsize - len, format, value);
 			if (len + written >= maxsize)
 				return false;
 			len += written;
 			return true;
 		};
 
+	const auto append_value_weird =
+		[&append_string, &append_value](long long value, int flag, int width) -> bool
+		{
+			char format[32];
+			char* ptr = format;
+			*ptr++ = '%';
+			if (flag == '+')
+				*ptr++ = '+';
+			*ptr++ = '0';
+			if (width != -1)
+				ptr += sprintf(ptr, "%d", width);
+			*ptr++ = 'l';
+			*ptr++ = 'l';
+			*ptr++ = 'd';
+			*ptr++ = '\0';
+
+			// idk why but musl libc test says that +4Y -> 2016 and +10F -> 2016-01-03
+			// i have no idea why the + is not printed in those cases :)
+			if (width < 11 && flag == '+')
+			{
+				char temp_buffer[12];
+				int nprint = sprintf(temp_buffer, format, value);
+				return append_string(temp_buffer + (nprint == width + 1));
+			}
+
+			return append_value(format, value);
+		};
+
 	while (*format && len < maxsize)
 	{
 		if (*format != '%')
@@ -194,20 +275,14 @@ size_t strftime(char* __restrict s, size_t maxsize, const char* __restrict forma
 		format++;
 
 		conversion_t conversion;
-		switch (*format)
-		{
-			case '+':
-			case '0':
-				conversion.flag = *format;
-				format++;
-				break;
-		}
+		if (*format == '0' || *format == '+')
+			conversion.flag = *format++;
 		if (isdigit(*format))
 		{
 			conversion.width = 0;
 			while (isdigit(*format))
 			{
-				conversion.width = (conversion.width * 10) + (*format + '0');
+				conversion.width = (conversion.width * 10) + (*format - '0');
 				format++;
 			}
 		}
@@ -247,16 +322,15 @@ size_t strftime(char* __restrict s, size_t maxsize, const char* __restrict forma
 				break;
 			case 'C':
 			{
-				if (conversion.flag == '\0')
-					conversion.flag = ' ';
-				if (conversion.flag == '+' && conversion.width <= 2)
-					conversion.flag = '0';
-				if (conversion.width < 2)
+				if (conversion.width == -1)
 					conversion.width = 2;
 
 				char new_format[32];
-				sprintf(new_format, "%%%c%dd", conversion.flag, conversion.width);
-				if (!append_value(new_format, timeptr->tm_year % 100))
+				if (conversion.flag == '+')
+					sprintf(new_format, "%%+0%dd", conversion.width);
+				else
+					sprintf(new_format, "%%0%dd", conversion.width);
+				if (!append_value(new_format, (1900 + timeptr->tm_year) / 100))
 					return 0;
 				break;
 			}
@@ -270,20 +344,24 @@ size_t strftime(char* __restrict s, size_t maxsize, const char* __restrict forma
 				else return 0;
 				break;
 			case 'e':
-				if (!append_value("% 2d", timeptr->tm_mday))
+				if (!append_value("%2d", timeptr->tm_mday))
 					return 0;
 				break;
 			case 'F':
 			{
-				if (conversion.flag == '\0')
-					conversion.flag = '+';
-				if (conversion.width == -1)
-					conversion.width = 10;
-				if (conversion.width < 6)
-					conversion.width = 6;
+				// remove trailing "-mm-dd" from width
+				if (conversion.width >= 6)
+					conversion.width -= 6;
 
 				char new_format[32];
-				sprintf(new_format, "%%%c%dY-%%m-%%d", conversion.flag, conversion.width - 6);
+				char* ptr = new_format;
+
+				*ptr++ = '%';
+				if (conversion.flag)
+					*ptr++ = conversion.flag;
+				if (conversion.width != -1)
+					ptr += sprintf(ptr, "%d", conversion.width);
+				strcpy(ptr, "Y-%m-%d");
 
 				if (size_t ret = strftime(s + len, maxsize - len, new_format, timeptr))
 					len += ret;
@@ -327,6 +405,13 @@ size_t strftime(char* __restrict s, size_t maxsize, const char* __restrict forma
 					len += ret;
 				else return 0;
 				break;
+			case 's':
+			{
+				struct tm tm_copy = *timeptr;
+				if (!append_value("%llu", mktime(&tm_copy)))
+					return 0;
+				break;
+			}
 			case 'S':
 				if (!append_value("%02d", timeptr->tm_sec))
 					return 0;
@@ -353,22 +438,10 @@ size_t strftime(char* __restrict s, size_t maxsize, const char* __restrict forma
 			{
 				// Adapted from GNU libc implementation
 
-				constexpr auto is_leap_year =
-					[](int year) -> bool
-					{
-						if (year % 400 == 0)
-							return true;
-						if (year % 100 == 0)
-							return false;
-						if (year % 4 == 0)
-							return true;
-						return false;
-					};
-
 				constexpr auto iso_week_days =
 					[](int yday, int wday) -> int
 					{
-						return yday - (wday + 382) % 7 + 3;
+						return yday - (yday - wday + 382) % 7 + 3;
 					};
 
 				int year = timeptr->tm_year + 1900;
@@ -396,20 +469,13 @@ size_t strftime(char* __restrict s, size_t maxsize, const char* __restrict forma
 							return 0;
 						break;
 					case 'G':
-					{
-						if (conversion.flag == '\0')
-							conversion.flag = ' ';
-						if (conversion.flag == '+' && conversion.width <= 4)
-							conversion.flag = '0';
+						if (conversion.flag == '\0' && 1900 + year > 9999)
+							conversion.flag = '+';
 						if (conversion.width == -1)
-							conversion.width = 0;
-
-						char new_format[32];
-						sprintf(new_format, "%%%c%dd", conversion.flag, conversion.width);
-						if (!append_value(new_format, year))
+							conversion.width = 4;
+						if (!append_value_weird(year, conversion.flag, conversion.width))
 							return 0;
 						break;
-					}
 					case 'V':
 						if (!append_value("%02d", days / 7 + 1))
 							return 0;
@@ -436,24 +502,17 @@ size_t strftime(char* __restrict s, size_t maxsize, const char* __restrict forma
 				else return 0;
 				break;
 			case 'y':
-				if (!append_value("%d", timeptr->tm_yday % 100))
+				if (!append_value("%02d", timeptr->tm_year % 100))
 					return 0;
 				break;
 			case 'Y':
-			{
-				if (conversion.flag == '\0')
-					conversion.flag = ' ';
-				if (conversion.flag == '+' && conversion.width <= 4)
-					conversion.flag = '0';
+				if (conversion.flag == '\0' && timeptr->tm_year > 9999 - 1900)
+					conversion.flag = '+';
 				if (conversion.width == -1)
-					conversion.width = 0;
-
-				char new_format[32];
-				sprintf(new_format, "%%%c%dd", conversion.flag, conversion.width);
-				if (!append_value(new_format, 1900 + timeptr->tm_year))
+					conversion.width = 4;
+				if (!append_value_weird(1900ll + timeptr->tm_year, conversion.flag, conversion.width))
 					return 0;
 				break;
-			}
 			case 'z':
 				// FIXME: support timezones
 				break;
@@ -483,8 +542,3 @@ void tzset()
 {
 	ASSERT_NOT_REACHED();
 }
-
-time_t mktime(struct tm*)
-{
-	ASSERT_NOT_REACHED();
-}

userspace/programs/CMakeLists.txt

@@ -1,11 +1,13 @@
 set(USERSPACE_PROGRAMS
 	bananfetch
+	basename
 	cat
 	cat-mmap
 	chmod
 	cp
 	dd
 	dhcp-client
+	dirname
 	DynamicLoader
 	echo
 	env
@@ -14,6 +16,7 @@ set(USERSPACE_PROGRAMS
 	id
 	image
 	init
+	ln
 	loadfont
 	loadkeys
 	ls

userspace/programs/basename/CMakeLists.txt

@@ -0,0 +1,8 @@
+set(SOURCES
+	main.cpp
+)
+
+add_executable(basename ${SOURCES})
+banan_link_library(basename libc)
+
+install(TARGETS basename OPTIONAL)

userspace/programs/basename/main.cpp

@@ -0,0 +1,30 @@
+#include <libgen.h>
+#include <stdio.h>
+#include <string.h>
+
+int usage(const char* argv0, int ret)
+{
+	FILE* fout = ret ? stderr : stdout;
+	fprintf(fout, "usage: %s STRING [SUFFIX]\n", argv0);
+	return ret;
+}
+
+int main(int argc, const char* argv[])
+{
+	if (argc != 2 && argc != 3)
+		return usage(argv[0], 1);
+
+	const char* result = basename(const_cast<char*>(argv[1]));
+	int result_len = strlen(result);
+
+	if (argc == 3)
+	{
+		int suffix_len = strlen(argv[2]);
+		if (result_len >= suffix_len && strcmp(result - suffix_len, argv[2]) == 0)
+			result_len -= suffix_len;
+	}
+
+	printf("%.*s\n", result_len, result);
+
+	return 0;
+}

userspace/programs/dirname/CMakeLists.txt

@@ -0,0 +1,8 @@
+set(SOURCES
+	main.cpp
+)
+
+add_executable(dirname ${SOURCES})
+banan_link_library(dirname libc)
+
+install(TARGETS dirname OPTIONAL)

userspace/programs/dirname/main.cpp

@@ -0,0 +1,18 @@
+#include <libgen.h>
+#include <stdio.h>
+
+int usage(const char* argv0, int ret)
+{
+	FILE* fout = ret ? stderr : stdout;
+	fprintf(fout, "usage: %s STRING\n", argv0);
+	return ret;
+}
+
+int main(int argc, const char* argv[])
+{
+	if (argc != 2)
+		return usage(argv[0], 1);
+	const char* result = dirname(const_cast<char*>(argv[1]));
+	printf("%s\n", result);
+	return 0;
+}

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)

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;
+}