SCANDIR(3)

NAME
scandir, scandirat, alphasort - scan a directory

SYNOPSIS
#include <sys/types.h>
#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
scandirat(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);

DESCRIPTION
The scandir() 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.

The select parameter is a pointer to a user-supplied subroutine which is called by scandir() 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 directory entries will be included.

The compar parameter 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 alphasort() function is a routine which can be used for the compar parameter to sort the array alphabetically.

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 scandirat() function is similar to scandir(), but takes an additional dirfd argument. 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.

DIAGNOSTICS
Returns -1 if the directory cannot be opened for reading or if malloc(3) cannot allocate enough memory to hold all the data structures.

SEE ALSO
malloc(3), opendir(3), qsort(3), dir(5)

STANDARDS
The scandir() and alphasort() functions conform to p1003.1-2008.

HISTORY
The scandir() and alphasort() functions appeared in 4.2BSD.

The argument types for alphasort() and for the compar argument to scandir() were originally void *, then changed to const void *, and then finally changed by p1003.1-2008 to their current form of const struct dirent **. Similarly, the select() argument to scandir() was originally struct dirent * until it was changed to its current form of const struct dirent *.