Manpages - scandir.3
Table of Contents
NAME
scandir, scandirat, alphasort, versionsort - scan a directory for matching entries
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.
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 *attributes*(7).
| Interface | Attribute | Value |
| *scandir*(), *scandirat*() | Thread safety | MT-Safe |
| *alphasort*(), *versionsort*() | 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 *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)
COLOPHON
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