readdir not reading subdirectories properly

[Laharl]

My Operating Systems professor has assigned homework that basically boils down to implementing ls -lra, but with a different output format. In other words, list the files and subdirectories (and a bit of data about them, for the files) in the current directory and its subdirectories using system calls. Unfortunately, it isn't working quite right. It works fine in the current directory, but when it goes into subdirectories, the stat() function always returns -1 (failure, error message is No such file or directory), yet when I print out the path and cd to the directory, the file is there. This is all occurring on FreeBSD 6.3 with gcc 3.4.6.

/* <name and email removed to protect the (sort of) innocent>
 * This program lists all files and directories contained within the present working directory and its subdirectories.
 * The following information is printed about each file: <filename> <size in bytes> <date and time last modified>
 */
 
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <dirent.h>
#include <errno.h>
#include <string.h>
#include <time.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/param.h>
 
extern int errno;
 
void read_directory(const char* dirpath, int numspaces);
void print_file(struct dirent* file, struct stat* sb, int numspaces, char isdir);
 
int main(){
    read_directory("./", 0);
    return 0;
}
 
void read_directory(const char* dirpath, int numspaces){
    struct dirent* entry;
    DIR* dir = opendir(dirpath);
    if (dir == NULL){
        perror("Error reading directory: ");
        return;
    }
    while ((entry = readdir(dir))){ //keep reading as long as there's something to read
        if (entry == NULL) //all done or an error
            return;
        else if ((strcmp(entry->d_name, ".") == 0) || (strcmp(entry->d_name, "..") == 0)) //need to avoid infinite recursion!
            continue;
        struct stat* sb = (struct stat*) (malloc(sizeof(struct stat*)));
        if (sb == NULL){
            printf("Error allocating for stat pointer!\n");
            return;
        }
        int i = stat(entry->d_name, sb); //This is the problematic call
        if (i == -1){
            printf("Attempting to read %s, but %s\n", entry->d_name, strerror(errno));
            return;
        }
        else if (S_ISDIR(sb->st_mode)){
            char* cwd = (char*)(malloc(MAXPATHLEN)); //gives 1023B
            cwd = getcwd(cwd, MAXPATHLEN);
            if (cwd == NULL){
                printf("Error allocating absolute pathname!\n");
                return;
            }
            sprintf(cwd, "%s/%s", cwd, entry->d_name);
            print_file(entry, sb, numspaces, 1);
            read_directory(cwd, numspaces+4);
            free(cwd);
        }
        else if (S_ISREG(sb->st_mode)){
            print_file(entry, sb, numspaces, 0);
        }
        free(sb);
    }
}
 
void print_file(struct dirent* file, struct stat* sb, int numspaces, char isdir){
    int i; //gcc 3.4 doesn't support bools as a builtin, seemingly
    char spaces[numspaces+1];
    spaces[numspaces] = '\0';
    for (i = 0; i < numspaces * sizeof(char); i++)
        spaces[i] = ' ';
    if (!isdir){
        char* clock = (char*)(malloc(27));
        if (clock == NULL){
            printf("Error allocating for clock characters!\n");
            return;
        }
        ctime_r(&(sb->st_mtime), clock);
        printf("%s%s %d %s", spaces, file->d_name, (unsigned int)(sb->st_size), clock);
        free(clock);
    }
    else
        printf("%s%s\n", spaces, file->d_name);
}

I have no idea what causes this, also when it goes into the subdirectories, it only looks at the first file if there's multiple. My only guess is that it might be an issue with how I obtain the absolute path...

[JosAH]

struct stat* sb = (struct stat*) (malloc(sizeof(struct stat*)));
 

The line above is line #39 in your program; you should allocate enough room for
an entire struct stat, not just enough room for a struct stat pointer.

kind regards,

Jos

[Laharl]

Whoops! Good catch on that one. Unfortunately, that doesn't fix the main problem.

[JosAH]

Then print out that dirpath parameter when you (recursively) enter that function
and see the constructed path names ...

kind regards,

Jos

edit: also the stat() function needs an absolute path name, not a relative one.

[Laharl]

Thanks a ton, Jos! It turned out to be a pathname issue to stat() after all.