I am trying to sort file names according to their sizes using a system call in c.

I tried this...

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

int main() {
    DIR *dir1, *dir2;
    int fd, cur_size, min_size;
    struct dirent *dirent1, *dirent2;
    struct stat st1, st2;
    char min_file_name[1000];
    char filename[1000];
    dir1 = opendir(".");
    while ((dirent1 = readdir(dir1)) != NULL) {
        min_size = INT_MAX;
        dir2 = opendir(".");
        while ((dirent2 = readdir(dir2)) != NULL) {
            stat(dirent2->d_name, &st1);
            cur_size = st1.st_size;
            strcpy(filename, dirent2->d_name);
            if (cur_size <= min_size && strcmp(min_file_name, filename) != 0) {
                min_size = cur_size;
                strcpy(min_file_name, dirent2->d_name);
            }
        }
        printf("File name = %s || size = %d \n", min_file_name, min_size);
    }
}

Output

amol@amol-Ideapad-320:~/AOS$ gcc q3.c
amol@amol-Ideapad-320:~/AOS$ ./a.out

File name =  || size = 0 
File name =  || size = 0 
File name =  || size = 0 
File name =  || size = 0 

CodePudding user response：

I'm afraid I don't understand the logic in your nested loop approach.

To produce a list in a given order, you can construct a sorted list of the entries in the directory and print that.

Here is a modified version using a simplistic quadratic insertion sort on a linked list:

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

struct entry {
    char *name;
    long long int size;
    struct entry *next;
};

int main() {
    DIR *dir;
    struct dirent *dp;
    struct stat st;
    struct entry *head = NULL, *ep, **npp;

    dir = opendir(".");
    if (dir == NULL) {
        perror("cannot open directory");
        return 1;
    }
    while ((dp = readdir(dir)) != NULL) {
        ep = calloc(sizeof(*ep), 1);
        if (ep == NULL) {
            perror("cannot allocate memory");
            return 1;
        }
        ep->name = strdup(dp->d_name);
        if (ep->name == NULL) {
            perror("cannot allocate memory");
            return 1;
        }
        if (!stat(dp->d_name, &st)) {
            ep->size = st.st_size;
        }
        for (npp = &head; *npp && (*npp)->size <= ep->size; npp = &(*npp)->next)
            continue;
        ep->next = *npp;
        *npp = ep;
    }
    closedir(dir);
    for (ep = head; ep; ep = ep->next) {
        printf("%s\n", ep->name);
    }
    while ((ep = head) != NULL) {
        head = ep->next;
        free(ep->name);
        free(ep);
    }
    return 0;
}