funny pwd

pwd.c

@@ -0,0 +1,132 @@
+#include <sys/stat.h>
+#include <dirent.h>
+#include <limits.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <mntent.h>
+
+#define ROOTINO     (2)
+#define BUFSZ       (128)
+
+typedef struct _mntdef{
+	char *mntpoint;
+	struct _mntdef *next;
+} mntdef;
+
+mntdef *mntlist = NULL;
+
+void addmntdef(char *name){
+	mntdef *m, *last = NULL;
+	last = mntlist;
+	if(last){
+		do{
+			if(strcmp(last->mntpoint, name) == 0) return;
+			if(last->next) last = last->next;
+			else break;
+		}while(1);
+	}
+	m = calloc(1, sizeof(mntdef));
+	m->mntpoint = strdup(name);
+	if(!last) mntlist = m;
+	else last->next = m;
+}
+
+
+void push_dir(char **old, char* new, size_t *len, size_t *L){
+	size_t dlen = strlen(new) + 2;
+	size_t plen = strlen(*old);
+	if(plen + dlen < *L){
+		*old = realloc(*old, plen + dlen);
+		*L = plen + dlen;
+	}
+	if(len)
+		memmove(*old + dlen - 1, *old, plen+1);
+	memcpy(*old + 1, new, dlen-2);
+	if(plen == 0) *(*old + dlen - 1) = 0;
+	**old = '/';
+}
+
+struct stat original_st;
+char *chkmounted(char *path){
+	mntdef *m = mntlist;
+	char p[1024];
+	struct stat st;
+	do{
+		snprintf(p, 1023, "%s%s", m->mntpoint, path);
+		stat(p, &st);
+		if(st.st_ino == original_st.st_ino){
+			if(strcmp("/", m->mntpoint))
+				return m->mntpoint + 1;
+			else
+				return NULL;
+		}
+		if(m->next) m = m->next;
+		else break;
+	}while(1);
+	return NULL;
+}
+
+char *pwd(char **path, size_t *len){
+	size_t L = 0;
+	struct dirent *dp;
+	struct stat st;
+	stat(".", &st);
+	if(!path) return NULL;
+	if(!*path){
+		*path = malloc(BUFSZ + 1);
+		**path = 0;
+		L = BUFSZ;
+		if(len) *len = BUFSZ;
+	}else{
+		if(len) L = *len;
+		else return NULL;
+	}
+	if(st.st_ino == ROOTINO){
+		char *m = NULL;
+		if((m = chkmounted(*path))) push_dir(path, m, len, &L);
+		if(**path != '/'){
+			**path = '/';
+			*(*path+1) = 0;
+		}
+		return *path;
+	}
+	DIR *dirp = opendir("..");
+	while((dp = readdir(dirp))){
+			if(strcmp(dp->d_name, ".") == 0 || strcmp(dp->d_name, "..") == 0)
+				continue;
+			if(st.st_ino == dp->d_ino){
+					push_dir(path, dp->d_name, len, &L);
+					chdir("..");
+					return pwd(path, &L);
+			}
+	}
+	chdir("..");
+	return pwd(path, &L);
+	closedir(dirp);
+	return *path;
+}
+
+
+int main(int argc, char **argv){
+	char *path = NULL;
+	struct stat st;
+	struct mntent *m;
+	FILE *f;
+	f = setmntent(_PATH_MOUNTED, "r");
+	while((m = getmntent(f))){
+		stat(m->mnt_dir, &st);
+		addmntdef(m->mnt_dir);
+	}
+	endmntent(f);
+	if(argc == 2){
+		if(chdir(argv[1])){
+			perror("chdir()");
+			return -1;
+		}
+	}
+	stat(".", &original_st);
+	puts(pwd(&path, NULL));
+	return 0;
+}