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.Dd $Mdocdate: June 17 2021 $ .Dt SCANDIR 3 .Os .Sh NAME .Nm scandir , .Nm scandirat , .Nm alphasort .Nd scan a directory .Sh SYNOPSIS n sys/types.h n dirent.h .Ft int .Fo scandir .Fa "const char *dirname" .Fa "struct dirent ***namelist" .Fa "int (*select)(const struct dirent *)" .Fa "int (*compar)(const struct dirent **, const struct dirent **)" .Fc .Ft int .Fo scandirat .Fa "int dirfd" .Fa "const char *dirname" .Fa "struct dirent ***namelist" .Fa "int (*select)(const struct dirent *)" .Fa "int (*compar)(const struct dirent **, const struct dirent **)" .Fc .Ft int .Fn alphasort "const struct dirent **d1" "const struct dirent **d2" .Sh DESCRIPTION The .Fn scandir function reads the directory .Fa dirname and builds an array of pointers to directory entries using .Xr 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 .Fa namelist .
p The .Fa select parameter is a pointer to a user-supplied subroutine which is called by .Fn 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 .Fa select is .Dv NULL , then all directory entries will be included.
p The .Fa compar parameter is a pointer to a user-supplied subroutine which is passed to .Xr qsort 3 to sort the completed array. If this pointer is .Dv NULL , the array is not sorted.
p The .Fn alphasort function is a routine which can be used for the .Fa compar parameter to sort the array alphabetically.
p The memory allocated for the array can be deallocated with .Xr free 3 , by freeing each pointer in the array and then the array itself.
p The .Fn scandirat function is similar to .Fn scandir , but takes an additional .Fa dirfd argument. If .Fa dirname is relative, .Fa dirfd must be a valid file descriptor referencing a directory, in which case the .Fa dirname lookup is performed relative to the directory referenced by .Fa dirfd . If .Fa dirfd has the special value .Va AT_FDCWD , then the current process directory is used as the base for relative lookups. See .Xr openat 2 for additional details. .Sh DIAGNOSTICS Returns -1 if the directory cannot be opened for reading or if .Xr malloc 3 cannot allocate enough memory to hold all the data structures. .Sh SEE ALSO .Xr malloc 3 , .Xr opendir 3 , .Xr qsort 3 , .Xr dir 5 .Sh STANDARDS The .Fn scandir and .Fn alphasort functions conform to .St -p1003.1-2008 . .Sh HISTORY The .Fn scandir and .Fn alphasort functions appeared in x 4.2 .
p The argument types for .Fn alphasort and for the .Fa compar argument to .Fn scandir were originally .Vt "void *" , then changed to .Vt "const void *" , and then finally changed by .St -p1003.1-2008 to their current form of .Vt "const struct dirent **" . Similarly, the .Fn select argument to .Fn scandir was originally .Vt "struct dirent *" until it was changed to its current form of .Vt "const struct dirent *" .