NAME

       scandir, scandirat, alphasort, versionsort - scan a directory for matching entries

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

       #include <dirent.h>

       int scandir(const char *restrict dirp,
                   struct dirent ***restrict namelist,
                   int (*filter)(const struct dirent *),
                   int (*compar)(const struct dirent **,
                                 const struct dirent **));

       int alphasort(const struct dirent **a, const struct dirent **b);
       int versionsort(const struct dirent **a, const struct dirent **b);

       #include <fcntl.h>          /* Definition of AT_* constants */
       #include <dirent.h>

       int scandirat(int dirfd, const char *restrict dirp,
                   struct dirent ***restrict namelist,
                   int (*filter)(const struct dirent *),
                   int (*compar)(const struct dirent **,
                                 const struct dirent **));

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       scandir(), alphasort():
           /* Since glibc 2.10: */ _POSIX_C_SOURCE >= 200809L
               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

       versionsort():
           _GNU_SOURCE

       scandirat():
           _GNU_SOURCE

DESCRIPTION

       The scandir() function scans the directory dirp, calling filter() on each directory entry.
       Entries for which filter() returns nonzero are stored in strings allocated via  malloc(3),
       sorted  using  qsort(3)  with  the  comparison  function  compar(), and collected in array
       namelist which is allocated via malloc(3).  If filter is NULL, all entries are selected.

       The alphasort() and versionsort()  functions  can  be  used  as  the  comparison  function
       compar().   The  former  sorts  directory  entries  using  strcoll(3),  the  latter  using
       strverscmp(3) on the strings (*a)->d_name and (*b)->d_name.

   scandirat()
       The scandirat() function operates in exactly the same way as  scandir(),  except  for  the
       differences described here.

       If  the  pathname  given  in  dirp  is  relative,  then  it is interpreted relative to the
       directory referred to by the file descriptor dirfd (rather than relative  to  the  current
       working  directory  of  the  calling  process,  as  is  done  by  scandir() for a relative
       pathname).

       If dirp is relative and dirfd is the special value  AT_FDCWD,  then  dirp  is  interpreted
       relative to the current working directory of the calling process (like scandir()).

       If dirp is absolute, then dirfd is ignored.

       See openat(2) for an explanation of the need for scandirat().

RETURN VALUE

       The  scandir() function returns the number of directory entries selected.  On error, -1 is
       returned, with errno set to indicate the error.

       The alphasort() and versionsort() functions return an integer  less  than,  equal  to,  or
       greater  than zero if the first argument is considered to be respectively less than, equal
       to, or greater than the second.

ERRORS

       EBADF  (scandirat()) dirp is relative but dirfd is  neither  AT_FDCWD  nor  a  valid  file
              descriptor.

       ENOENT The path in dirp does not exist.

       ENOMEM Insufficient memory to complete the operation.

       ENOTDIR
              The path in dirp is not a directory.

       ENOTDIR
              (scandirat())  dirp is a relative pathname and dirfd is a file descriptor referring
              to a file other than a directory.

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).

       ┌────────────────────────────────────────────────────────┬───────────────┬────────────────┐
       │Interface                                               │ Attribute     │ Value          │
       ├────────────────────────────────────────────────────────┼───────────────┼────────────────┤
       │scandir(), scandirat()                                  │ Thread safety │ MT-Safe        │
       ├────────────────────────────────────────────────────────┼───────────────┼────────────────┤
       │alphasort(), versionsort()                              │ Thread safety │ MT-Safe locale │
       └────────────────────────────────────────────────────────┴───────────────┴────────────────┘

STANDARDS

       alphasort()
       scandir()
              POSIX.1-2008.

       versionsort()
       scandirat()
              GNU.

HISTORY

       alphasort()
       scandir()
              4.3BSD, POSIX.1-2008.

       versionsort()
              glibc 2.1.

       scandirat()
              glibc 2.15.

NOTES

       Since glibc 2.1, alphasort() calls strcoll(3); earlier it used strcmp(3).

       Before glibc 2.10, the two arguments of alphasort() and versionsort() were typed as  const
       void *.   When  alphasort()  was  standardized  in  POSIX.1-2008,  the  argument  type was
       specified as the type-safe const struct dirent **, and glibc 2.10 changed  the  definition
       of alphasort() (and the nonstandard versionsort()) to match the standard.

EXAMPLES

       The program below prints a list of the files in the current directory in reverse order.

   Program source

       #define _DEFAULT_SOURCE
       #include <dirent.h>
       #include <stdio.h>
       #include <stdlib.h>

       int
       main(void)
       {
           struct dirent **namelist;
           int n;

           n = scandir(".", &namelist, NULL, alphasort);
           if (n == -1) {
               perror("scandir");
               exit(EXIT_FAILURE);
           }

           while (n--) {
               printf("%s\n", namelist[n]->d_name);
               free(namelist[n]);
           }
           free(namelist);

           exit(EXIT_SUCCESS);
       }

SEE ALSO

       closedir(3),  fnmatch(3),  opendir(3),  readdir(3),  rewinddir(3),  seekdir(3), strcmp(3),
       strcoll(3), strverscmp(3), telldir(3)