unlink.c

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// -*-Mode: C++;-*- // technically C99

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/*
 *  Function to recursively unlink a directory hierarchy.
 */

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

#include "unlink.h"


/*
 *  Unlink the tree hierarchy rooted at "path" (helper function).
 *  path_len = strlen(path),
 *  max_len = length of buffer for path.
 *
 *  Stevens describes this technique of using a single buffer for the
 *  path names in "Advanced Programming in the Unix Environment",
 *  Section 4.21 (Reading Directories).
 *
 *  Returns: 0 on success, or else the number of unlink() or rmdir()
 *  calls that failed.
 */
static int
do_unlink_tree(char *path, int path_len, int max_len)
{
    DIR *dirp;
    struct dirent *dent;
    struct stat sb;
    int len, num_failures;

    /*
     * Use unlink(2) for anything that's not a directory.
     */
    if (lstat(path, &sb) != 0)
        return (1);
    if (! S_ISDIR(sb.st_mode))
        return (unlink(path) ? 1 : 0);

    /*
     * Recursively unlink directory entries, except "." and "..".
     */
    dirp = opendir(path);
    if (dirp == NULL)
        return (1);
    num_failures = 0;
    path[path_len] = '/';
    while ((dent = readdir(dirp)) != NULL) {
        if (strncmp(dent->d_name, ".", 2) == 0 ||
            strncmp(dent->d_name, "..", 3) == 0)
            continue;
        len = strlen(dent->d_name);
        if (path_len + len + 2 >= max_len) {
            num_failures++;
        } else {
            strcpy(&path[path_len + 1], dent->d_name);
            num_failures += do_unlink_tree(path, path_len + len + 1, max_len);
        }
    }
    path[path_len] = 0;
    closedir(dirp);

    /*
     * Finally, rmdir(2) the directory.
     */
    if (rmdir(path) != 0)
        num_failures++;

    return (num_failures);
}

/*
 *  Unlink the file hierarchy rooted at "path".
 *
 *  Returns: 0 on success, or else the number of unlink() or rmdir()
 *  calls that failed.
 */
#define BUF_LEN  4096
int
unlink_tree(char *path)
{
    char buf[BUF_LEN];
    int len;

    len = strlen(path);
    if (len >= BUF_LEN)
        return (1);
    strcpy(buf, path);
    return do_unlink_tree(buf, len, BUF_LEN);
}