scandir, scandirat, alphasort, versionsort - scan a directory for matching
entries
Standard C library (
libc,
-lc)
#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 **));
scandir(),
alphasort():
/* Since glibc 2.10: */ _POSIX_C_SOURCE >= 200809L
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
versionsort():
_GNU_SOURCE
scandirat():
_GNU_SOURCE
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.
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().
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.
- 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.
versionsort() was added in glibc 2.1.
scandirat() was added in glibc 2.15.
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 |
alphasort(),
scandir(): 4.3BSD, POSIX.1-2008.
versionsort() and
scandirat() are GNU extensions.
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.
The program below prints a list of the files in the current directory in reverse
order.
#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);
}
closedir(3),
fnmatch(3),
opendir(3),
readdir(3),
rewinddir(3),
seekdir(3),
strcmp(3),
strcoll(3),
strverscmp(3),
telldir(3)