ece282/lab05/spwd.c

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <dirent.h>
#include <string.h>
#include <unistd.h>

ino_t get_inode(char *);
void printpathto(ino_t);
void inum_to_name(ino_t, char *, int);

int main() {
    printpathto(get_inode(".")); /* Print path to current directory */
    putchar('\n');               /* Newline after path */
    return 0;
}

void printpathto(ino_t this_inode) {
    ino_t parent_inode;
    char its_name[BUFSIZ];

    parent_inode = get_inode("..");

    if (this_inode == parent_inode) { 
        /* Base case: we are at the root directory */
        printf("/");
        return;
    }

    chdir("..");  /* Move up one directory */
    inum_to_name(this_inode, its_name, BUFSIZ); /* Get directory name */

    printpathto(parent_inode); /* Recursive call */

    /* Ensure correct formatting: No extra slash */
    if (strcmp(its_name, "/") != 0) {
        if (parent_inode != this_inode) { /* Avoid leading double slash */
            printf("%s%s", (parent_inode == get_inode(".")) ? "" : "/", its_name);
        }
    }
}

void inum_to_name(ino_t inode_to_find, char *namebuf, int buflen) {
    DIR *dir_ptr;
    struct dirent *direntp;

    dir_ptr = opendir(".");
    if (dir_ptr == NULL) {
        perror("opendir");
        exit(1);
    }

    while ((direntp = readdir(dir_ptr)) != NULL) {
        if (direntp->d_ino == inode_to_find) {
            strncpy(namebuf, direntp->d_name, buflen);
            namebuf[buflen - 1] = '\0';  /* Ensure null termination */
            closedir(dir_ptr);
            return;
        }
    }

    fprintf(stderr, "Error: inode %lu not found in directory\n", (unsigned long)inode_to_find);
    closedir(dir_ptr);
    exit(1);
}

ino_t get_inode(char *fname) {
    struct stat info;

    if (stat(fname, &info) == -1) {
        fprintf(stderr, "Cannot stat ");
        perror(fname);
        exit(1);
    }
    return info.st_ino;
}