scandir

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 **));

Status

Implemented

Conformance

IEEE Std 1003.1-2017

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.

The alphasort() function shall 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.

The scandir() function shall scan the directory dir, calling the function referenced by sel on each directory entry. Entries for which the function referenced by sel returns non-zero shall be stored in strings allocated as if by a call to malloc(), and sorted as if by a call to qsort() with the comparison function compar, except that compar need not provide total ordering. The strings are collected in array namelist which shall be allocated as if by a call to malloc(). If sel is a null pointer, all entries shall be selected. If the comparison function compar does not provide total ordering, the order in which the directory entries are stored is unspecified. If compar is a null pointer, the entries are not sorted.

Return value

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

Errors

The scandir() function shall fail 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 path name is longer than the name length limit of the filesystem, which may differ from NAME_MAX (see POSIX deviations).

  • 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.

The scandir() function may fail if:

  • 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 path name exceeds {PATH_MAX}, or path name 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.

POSIX deviations

The length of a path name component is not checked against NAME_MAX by libphoenix, but by the filesystem server, against the name length limit of the filesystem, which may differ from NAME_MAX. The error reported for a too long component of the path name therefore depends on the filesystem (see the deviations of open()).