how to get the size of a dir programatically in linux?

问题

I want to get the exact size of a particular dir in linux through a C program. I tried using statfs(path,struct statfs &) but it doesn't give exact size. I also tried with stat() but it returns size as 4096 for any dir !

Please suggest me the way through which I can get the exact size of dir just like we get after "du -sh dirPath" command.

Also I dont wanna use du through system().

Thanks in advance.

回答1:

Typical Solution

If you want the size of a directory, similar in fashion to du, create a recursive function. It is possible to solve the problem iteratively, but the solution lends itself to recursion.

Information

Here is a link to get you started:

http://www.cs.utk.edu/~plank/plank/classes/cs360/360/notes/Prsize/lecture.html

Search

Search Google with 'stat c program recursive directory size'

Example

Directly from Jim Plank's website, serving as an example to get you started.

#include <stdio.h>
#include <dirent.h>
#include <sys/stat.h>

main()
{
  DIR *d;
  struct dirent *de;
  struct stat buf;
  int exists;
  int total_size;

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

  total_size = 0;

  for (de = readdir(d); de != NULL; de = readdir(d)) {
    exists = stat(de->d_name, &buf);
    if (exists < 0) {
      fprintf(stderr, "Couldn't stat %s\n", de->d_name);
    } else {
      total_size += buf.st_size;
    }
  }
  closedir(d);
  printf("%d\n", total_size);
}

回答2:

You need to stat() all the files in the current directory and sub directories and add them up.

Consider using a recursive algorithm for this.

回答3:

If you do not want to use 'system', but are ok to use 'pipe', 'fork', 'execlp' and 'du', you could build a pipe, fork a new process, redirect 'STDOUT' of the child in the pipe, exec 'du' in the child, and read the result in the parent. A sample code would be:

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int main(void) {
  int pfd[2], n;
  char str[1000];

  if (pipe(pfd) < 0) {
    printf("Oups, pipe failed.  Exiting\n");
    exit(-1);
  }

  n = fork();

  if (n < 0) {
    printf("Oups, fork failed.  Exiting\n");
    exit(-2);
  } else if (n == 0) {
    close(pfd[0]);

    dup2(pfd[1], 1);
    close(pfd[1]);

    execlp("du", "du", "-sh", "/tmp", (char *) 0);
    printf("Oups, execlp failed.  Exiting\n"); /* This will be read by the  parent. */
    exit(-1); /* To avoid problem if execlp fails, especially if in a loop. */
  } else {
    close(pfd[1]);

    n = read(pfd[0], str, 1000); /* Should be done in a loop until read return 0, but I am lazy. */
    str[n] = '\0';

    close(pfd[0]);
    wait(&n); /* To avoid the zombie process. */

    if (n == 0) {
       printf("%s", str);
    } else {
       printf("Oups, du or execlp failed.\n");
    }
  }
}

回答4:

I guess the solution may be useful for those who still may encounter the problem.

Here's the function that was written to imitate linux du program. It recursively goes through all directories and adds up file sizes.

Note, that this function is still incomplete, since it behaves incorrectly on hard links. One should add a container to store file descriptors that point to the same inode entity and use that to get rid of multiple counts of the very same file. lstat() is used to handle symlinks (aka soft links), hard links is an issue here.

size_t countDiskUsage(const char* pathname)
{
  if (pathname == NULL) {
    printf("Erorr: pathname is NULL\n");
  }

  struct stat stats;

  if (lstat(pathname, &stats) == 0) {
    if (S_ISREG(stats.st_mode)){
      return stats.st_size;
    }
  } else {
    perror("lstat\n");
  }

  DIR* dir = opendir(pathname);

  if (dir == NULL) {
    perror("Error");
    return 0;
  }

  struct dirent *dirEntry;
  size_t totalSize = 4096;

  for (dirEntry = readdir(dir); dirEntry != NULL; dirEntry =   readdir(dir)) {
    long pathLength = sizeof(char) * (strlen(pathname) + strlen(dirEntry->d_name) + 2);
    char* name = (char*)malloc(pathLength);
    strcpy(name, pathname);
    strcpy(name + strlen(pathname), "/");
    strcpy(name + strlen(pathname) + 1, dirEntry->d_name);

    if (dirEntry->d_type == DT_DIR) {
      if (strcmp(dirEntry->d_name, ".") != 0 && strcmp(dirEntry->d_name, "..") != 0) {
        totalSize += countDiskUsage(name);
      }
    } else {
      int status = lstat(name, &stats);
      if (status == 0) {
        totalSize += stats.st_size;
      } else {
        perror("lstat\n");
      }
    }
    free(name);
  }

  closedir(dir);

  return totalSize;
}

来源：https://stackoverflow.com/questions/1129499/how-to-get-the-size-of-a-dir-programatically-in-linux