From 5e90292fcb70670916844210d2f6248c78a1d870 Mon Sep 17 00:00:00 2001
From: Alan Potteiger <alanpotteiger@gmail.com>
Date: Tue, 22 Nov 2022 23:09:54 +0100
Subject: [PATCH] `pwd` implemented

---
 Makefile |  2 +-
 pwd.c    | 78 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 79 insertions(+), 1 deletion(-)
 create mode 100644 pwd.c

diff --git a/Makefile b/Makefile
index b96096d..3de3641 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-BIN=sleep cat
+BIN=cat pwd sleep
 CFLAGS=-std=c99
 all: $(BIN)
 clean:
diff --git a/pwd.c b/pwd.c
new file mode 100644
index 0000000..308a57a
--- /dev/null
+++ b/pwd.c
@@ -0,0 +1,78 @@
+/* `pwd.c` - return working directory name
+   Copyright (c) 2022, Alan Potteiger
+   See `LICENSE` for copyright and license details */
+
+#define _POSIX_C_SOURCE 200809L
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+static const char *usage = {
+	"usage: pwd [-L|-P]\n"
+};
+
+int
+main(int argc, char *argv[])
+{
+	char c;
+	char *wd, *p;
+	int flag;
+
+	/* 0 == -L
+	   1 == -P */
+	flag = 0;
+
+	while ((c = getopt(argc, argv, "LP")) != -1) {
+		switch (c) {
+		case 'L':
+			flag = 0;
+			break;
+		case 'P':
+			flag = 1;
+			break;
+		case '?':
+		default:
+			fputs(usage, stderr);
+			return 1;
+		}
+	}
+
+	if (flag)
+		goto pflag;
+
+	/* -L */
+	wd = getenv("PWD");
+	if (wd == NULL)
+		goto pflag;
+
+	/* test pathname from $PWD for ./ or ../
+	   if they exist, jump to the -P option */
+	p = wd;
+	for (; *p != '\0'; p++) {
+		if (*p == '/')
+			continue;
+		if (*p == '.') {
+			if (*(p+1) == '.' && *(p+1) == '/')
+				goto pflag;
+			if (*(p+1) == '/')
+				goto pflag;
+		}
+	}
+
+	printf("%s\n", wd);
+	return 0;
+
+pflag:	/* -P */
+	wd = getcwd(NULL, 0);
+	if (wd == NULL) {
+		perror("pwd");
+		return 1;
+	}
+
+	printf("%s\n", wd);
+
+	free(wd);
+	return 0;
+}
+
-- 
2.11.4.GIT