SCANDIR(3) Library Functions Manual SCANDIR(3)

scandir, fdscandir, scandirat, scandir_b, fdscandir_b, fdscandirat_b, alphasort — scan a directory

Standard C Library (libc, -lc)

#include <dirent.h>

int
scandir(const char *dirname, struct dirent ***namelist, int (*select)(const struct dirent *), int (*compar)(const struct dirent **, const struct dirent **));

int
fdscandir(int dirfd, struct dirent ***namelist, int (*select)(const struct dirent *), int (*compar)(const struct dirent **, const struct dirent **));

int
scandirat(int dirfd, const char *dirname, struct dirent ***namelist, int (*select)(const struct dirent *), int (*compar)(const struct dirent **, const struct dirent **));

int
scandir_b(const char *dirname, struct dirent ***namelist, int (^select)(const struct dirent *), int (^compar)(const struct dirent **, const struct dirent **));

int
fdscandir_b(int dirfd, struct dirent ***namelist, int (^select)(const struct dirent *), int (^compar)(const struct dirent **, const struct dirent **));

int
scandirat_b(int dirfd, const char *dirname, struct dirent ***namelist, int (^select)(const struct dirent *), int (^compar)(const struct dirent **, const struct dirent **));

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

The () function reads the directory dirname and builds an array of pointers to directory entries using malloc(3). It returns the number of entries in the array. A pointer to the array of directory entries is stored in the location referenced by namelist (even if no entries were selected).

The select argument is a pointer to a user supplied subroutine which is called by () to select which entries are to be included in the array. The select routine is passed a pointer to a directory entry and should return a non-zero value if the directory entry is to be included in the array. If select is null, then all the directory entries will be included.

The compar argument is a pointer to a user supplied subroutine which is passed to qsort(3) to sort the completed array. If this pointer is null, the array is not sorted.

The () function is a routine which can be used for the compar argument to sort the array alphabetically using strcoll(3).

The memory allocated for the array can be deallocated with free(3), by freeing each pointer in the array and then the array itself.

The () function is similar to scandir(), but takes a file descriptor referencing a directory instead of a path. The file descriptor is left open on return, regardless of outcome.

The () function is similar to scandir(), but takes an additional dirfd argument. If the supplied dirname is absolute, the function's behavior is identical to that of scandir(), the dirfd argument is unused. If dirname is relative, dirfd must be a valid file descriptor referencing a directory, in which case the dirname lookup is performed relative to the directory referenced by dirfd. If dirfd has the special value AT_FDCWD, then the current process directory is used as the base for relative lookups. See openat(2) for additional details.

The (), (), and () functions behave in the same way as scandir(), fdscandir(), and scandirat(), respectively, but take blocks as arguments instead of function pointers and call () rather than ().

The scandir(), fdscandir(), scandirat(), scandir_b(), fdscandir_b(), and scandirat_b() functions return the number of directory entries found on succes. If the directory cannot be opened for reading, an error occurs while reading the directory, or malloc(3) cannot allocate enough memory to hold all the directory entries, they return -1 and set errno to an appropriate value.

The scandir(), scandirat(), scandir_b(), and scandirat_b() functions may fail and set errno for any of the errors specified for the opendir(3), malloc(3), readdir(3), and closedir(3) functions.

The fdscandir() and fdscandir_b() functions may fail and set errno for any of the errors specified for the fdopendir(3), malloc(3), readdir(3), and closedir(3) functions.

openat(2), directory(3), malloc(3), qsort(3), strcoll(3), dir(5)

The alphasort() and scandir() functions are expected to conform to IEEE Std 1003.1-2008 (“POSIX.1”). The scandirat() function is a GNU extension and conforms to no standard. The fdscandir(), scandir_b(), fdscandir_b(), and scandirat_b() functions are FreeBSD extensions.

The scandir() and alphasort() functions appeared in 4.2BSD. The scandir_b() function was added in FreeBSD 11.0. The scandirat() function was added in FreeBSD 13.2. The fdscandir(), fdscandir_b(), and scandirat_b() functions were added in FreeBSD 15.0.

June 25, 2025 Mac OS X 13