pgcheckdir.c

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/*-------------------------------------------------------------------------
 *
 * pgcheckdir.c
 *
 * A simple subroutine to check whether a directory exists and is empty or not.
 * Useful in both initdb and the backend.
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *      src/port/pgcheckdir.c
 *-------------------------------------------------------------------------
 */
 
#include "c.h"
 
#include <dirent.h>
 
 
/*
 * Test to see if a directory exists and is empty or not.
 *
 * Returns:
 *      0 if nonexistent
 *      1 if exists and empty
 *      2 if exists and contains _only_ dot files
 *      3 if exists and contains a mount point
 *      4 if exists and not empty
 *      -1 if trouble accessing directory (errno reflects the error)
 */
int
pg_check_dir(const char *dir)
{
    int         result = 1;
    DIR        *chkdir;
    struct dirent *file;
    bool        dot_found = false;
    bool        mount_found = false;
    int         readdir_errno;
 
    chkdir = opendir(dir);
    if (chkdir == NULL)
        return (errno == ENOENT) ? 0 : -1;
 
    while (errno = 0, (file = readdir(chkdir)) != NULL)
    {
        if (strcmp(".", file->d_name) == 0 ||
            strcmp("..", file->d_name) == 0)
        {
            /* skip this and parent directory */
            continue;
        }
#ifndef WIN32
        /* file starts with "." */
        else if (file->d_name[0] == '.')
        {
            dot_found = true;
        }
        /* lost+found directory */
        else if (strcmp("lost+found", file->d_name) == 0)
        {
            mount_found = true;
        }
#endif
        else
        {
            result = 4;         /* not empty */
            break;
        }
    }
 
    if (errno)
        result = -1;            /* some kind of I/O error? */
 
    /* Close chkdir and avoid overwriting the readdir errno on success */
    readdir_errno = errno;
    if (closedir(chkdir))
        result = -1;            /* error executing closedir */
    else
        errno = readdir_errno;
 
    /* We report on mount point if we find a lost+found directory */
    if (result == 1 && mount_found)
        result = 3;
 
    /* We report on dot-files if we _only_ find dot files */
    if (result == 1 && dot_found)
        result = 2;
 
    return result;
}