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versionsort(3)

SCANDIR(3)                 Linux Programmer's Manual                SCANDIR(3)

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

SYNOPSIS
       #include <dirent.h>

       int scandir(const char *dirp, struct dirent ***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 *dirp, struct dirent ***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 versions <= 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 se‐
       lected.

       The alphasort() and versionsort() functions can be used as the compari‐
       son function compar().  The former sorts directory entries  using  str‐
       coll(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 rela‐
       tive  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  se‐
       lected.  On error, -1 is returned, with errno set to indicate the cause
       of the error.

       The  alphasort()  and  versionsort()  functions  return an integer less
       than, equal to, or greater than zero if the first argument  is  consid‐
       ered  to  be respectively less than, equal to, or greater than the sec‐
       ond.

ERRORS
       ENOENT The path in dirp does not exist.

       ENOMEM Insufficient memory to complete the operation.

       ENOTDIR
              The path in dirp is not a directory.

       The following additional errors can occur for scandirat():

       EBADF  dirfd is not a valid file descriptor.

       ENOTDIR
              dirp is a relative path and dirfd is a file descriptor referring
              to a file other than a directory.

VERSIONS
       versionsort() was added to glibc in version 2.1.

       scandirat() was added to glibc in version 2.15.

ATTRIBUTES
       For an explanation of the terms  used  in  this  section,  see  attrib‐
       utes(7).   allbox;  lbw26  lb  lb  l l l.  Interface Attribute Value T{
       scandir(), scandirat() T}   Thread safety  MT-Safe T{ alphasort(), ver‐
       sionsort() T}   Thread safety  MT-Safe locale


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

       versionsort() and scandirat() are GNU extensions.

NOTES
       Since glibc 2.1, alphasort() calls strcoll(3);  earlier  it  used  str‐
       cmp(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.

EXAMPLE
       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)

COLOPHON
       This  page  is  part of release 5.02 of the Linux man-pages project.  A
       description of the project, information about reporting bugs,  and  the
       latest     version     of     this    page,    can    be    found    at
       https://www.kernel.org/doc/man-pages/.

GNU                               2017-09-15                        SCANDIR(3)
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