src/port/pgcheckdir.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * pgcheckdir.c
   4  *
   5  * A simple subroutine to check whether a directory exists and is empty or not.
   6  * Useful in both initdb and the backend.
   7  *
   8  * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
   9  * Portions Copyright (c) 1994, Regents of the University of California
  10  *
  11  * IDENTIFICATION
  12  *              src/port/pgcheckdir.c
  13  *-------------------------------------------------------------------------
  14  */
  15
  16 #include "c.h"
  17
  18 #include <dirent.h>
  19
  20
  21 /*
  22  * Test to see if a directory exists and is empty or not.
  23  *
  24  * Returns:
  25  *              0 if nonexistent
  26  *              1 if exists and empty
  27  *              2 if exists and contains _only_ dot files
  28  *              3 if exists and contains a mount point
  29  *              4 if exists and not empty
  30  *              -1 if trouble accessing directory (errno reflects the error)
  31  */
  32 int
  33 pg_check_dir(const char *dir)
  34 {
  35         int                     result = 1;
  36         DIR                *chkdir;
  37         struct dirent *file;
  38         bool            dot_found = false;
  39         bool            mount_found = false;
  40         int                     readdir_errno;
  41
  42         chkdir = opendir(dir);
  43         if (chkdir == NULL)
  44                 return (errno == ENOENT) ? 0 : -1;
  45
  46         while (errno = 0, (file = readdir(chkdir)) != NULL)
  47         {
  48                 if (strcmp(".", file->d_name) == 0 ||
  49                         strcmp("..", file->d_name) == 0)
  50                 {
  51                         /* skip this and parent directory */
  52                         continue;
  53                 }
  54 #ifndef WIN32
  55                 /* file starts with "." */
  56                 else if (file->d_name[0] == '.')
  57                 {
  58                         dot_found = true;
  59                 }
  60                 /* lost+found directory */
  61                 else if (strcmp("lost+found", file->d_name) == 0)
  62                 {
  63                         mount_found = true;
  64                 }
  65 #endif
  66                 else
  67                 {
  68                         result = 4;                     /* not empty */
  69                         break;
  70                 }
  71         }
  72
  73         if (errno)
  74                 result = -1;                    /* some kind of I/O error? */
  75
  76         /* Close chkdir and avoid overwriting the readdir errno on success */
  77         readdir_errno = errno;
  78         if (closedir(chkdir))
  79                 result = -1;                    /* error executing closedir */
  80         else
  81                 errno = readdir_errno;
  82
  83         /* We report on mount point if we find a lost+found directory */
  84         if (result == 1 && mount_found)
  85                 result = 3;
  86
  87         /* We report on dot-files if we _only_ find dot files */
  88         if (result == 1 && dot_found)
  89                 result = 2;
  90
  91         return result;
  92 }