Implementation status: to be implemented

Synopsis

#include <dirent.h>

int alphasort(const struct dirent **d1, const struct dirent **d2);

int scandir(const char *dir, struct dirent ***namelist, int (*sel)(const struct dirent *), int (*compar)(const struct dirent **, const struct dirent **));

Description

The alphasort() function can be used as the comparison function for the scandir() function to sort the directory entries, d1 and d2, into alphabetical order. Sorting happens as if by calling the strcoll() function on the d_name element of the dirent structures passed as the two parameters. If the strcoll() function fails, the return value of alphasort() is unspecified.

Arguments:

For alphasort():
d1, d2 - directory entries to be compared.

For scandir():
dir - the directory to be scanned,
namelist - a resulting array which is allocated as if by a call to malloc(),
sel - a pointer to the function to be called on each directory entry,
compar - the comparison function.

If sel is a null pointer, all entries are selected.
If the comparison function compar does not provide total ordering, the order in which the directory entries are stored is unspecified.

Return value

Upon successful completion, the alphasort() function returns greater than, equal to, or less than 0, according to whether the name of the directory entry pointed to by d1 is lexically greater than, equal to, or less than the directory pointed to by d2 when both are interpreted as appropriate to the current locale. There is no return value reserved to indicate an error.

Upon successful completion, the scandir() function returns the number of entries in the array and a pointer to the array through the parameter namelist. Otherwise, the scandir() function returns -1.

Errors

No errors are defined for the alphasort() function.

The scandir() function fails if
[EACCES] - search permission is denied for the component of the path prefix of dir or read permission is denied for dir.
[ELOOP] - a loop exists in symbolic links encountered during resolution of the dir argument.
[ENAMETOOLONG] - The length of a component of a pathname is longer than {NAME_MAX}.
[ENOENT] - A component of dir does not name an existing directory or dir is an empty string.
[ENOMEM] - Insufficient storage space is available.
[ENOTDIR] - A component of dir names an existing file that is neither a directory nor a symbolic link to a directory.
[EOVERFLOW] - One of the values to be returned or passed to a callback function cannot be represented correctly.
[ELOOP] - More than {SYMLOOP_MAX} symbolic links were encountered during resolution of the dir argument.
[EMFILE] - All file descriptors available to the process are currently open.
[ENAMETOOLONG] - The length of a pathname exceeds {PATH_MAX}, or pathname resolution of a symbolic link produced an intermediate result with a length that exceeds {PATH_MAX}.
[ENFILE] - Too many files are currently open in the system.

Comments

The alphasort() function does not change the setting of errno if successful. Since no return value is reserved to indicate an error, an application wishing to check for error situations should set errno to 0, then call alphasort(), then check errno.