SCANDIR(3) | Library Functions Manual | SCANDIR(3)

# NAME

`scandir`, `alphasort` —
scan a directory

# LIBRARY

Standard C Library (libc, -lc)

# 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
`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 the 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.

# 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

directory(3), dirent(3), malloc(3), qsort(3)

# STANDARDS

The `scandir`() and `alphasort`() functions conform to IEEE Std 1003.1-2008 (“POSIX.1”).

# HISTORY

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

They were changed in NetBSD 8.0 to use “struct dirent **” instead of “void *” for the comparison function, including `alphasort`().

December 15, 2016 | NetBSD 9.5