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28.\" @(#)scandir.3 8.1 (Berkeley) 6/4/93
29.\" $FreeBSD: src/lib/libc/gen/scandir.3,v 1.9 2007/01/09 00:27:55 imp Exp $
30.\"
31.Dd May 20, 2008
32.Dt SCANDIR 3
33.Os
34.Sh NAME
35.Nm scandir ,
36#ifdef UNIFDEF_BLOCKS
37.Nm scandir_b ,
38#endif
39.Nm alphasort
40.Nd scan a directory
41.Sh SYNOPSIS
42.In sys/types.h
43.In dirent.h
44.Ft int
45.Fn scandir "const char *dirname" "struct dirent ***namelist" "int \\*(lp*select\\*(rp\\*(lpstruct dirent *\\*(rp" "int \\*(lp*compar\\*(rp\\*(lpconst void *, const void *\\*(rp"
46.Ft int
47.Fn alphasort "const void *d1" "const void *d2"
48#ifdef UNIFDEF_BLOCKS
49.Ft int
50.Fn scandir_b "const char *dirname" "struct dirent ***namelist" "int \\*(lp^select\\*(rp\\*(lpstruct dirent *\\*(rp" "int \\*(lp^compar\\*(rp\\*(lpconst void *, const void *\\*(rp"
51#endif
52.Sh DESCRIPTION
53The
54.Fn scandir
55function
56reads the directory
57.Fa dirname
58and builds an array of pointers to directory
59entries using
60.Xr malloc 3 .
61It returns the number of entries in the array.
62A pointer to the array of directory entries is stored in the location
63referenced by
64.Fa namelist .
65.Pp
66The
67.Fa select
68argument is a pointer to a user supplied subroutine which is called by
69.Fn scandir
70to select which entries are to be included in the array.
71The select routine is passed a
72pointer to a directory entry and should return a non-zero
73value if the directory entry is to be included in the array.
74If
75.Fa select
76is null, then all the directory entries will be included.
77.Pp
78The
79.Fa compar
80argument is a pointer to a user supplied subroutine which is passed to
81.Xr qsort 3
82to sort the completed array.
83If this pointer is null, the array is not sorted.
84Note that from within the
85.Fa compar
86subroutine, the two arguments are of type
87.Ft const struct dirent ** ,
88so that a double-dereference is needed to access the fields in the
89.Ft dirent
90structure.
91.Pp
92The
93.Fn alphasort
94function
95is a routine which can be used for the
96.Fa compar
97argument to sort the array alphabetically.
98.Pp
99The memory allocated for the array can be deallocated with
100.Xr free 3 ,
101by freeing each pointer in the array and then the array itself.
102#ifdef UNIFDEF_BLOCKS
103.Pp
104The
105.Fn scandir_b
106function works the same way as the
107.Fn scandir
108function, except that
109.Fa select
110and
111.Fa compar
112are blocks instead of subroutines.
113#endif
114.Sh DIAGNOSTICS
115Returns \-1 if the directory cannot be opened for reading or if
116.Xr malloc 3
117cannot allocate enough memory to hold all the data structures.
118.Sh SEE ALSO
119.Xr directory 3 ,
120.Xr malloc 3 ,
121.Xr qsort 3 ,
122.Xr dir 5
123.Sh HISTORY
124The
125.Fn scandir
126and
127.Fn alphasort
128functions appeared in
129.Bx 4.2 .
130#ifdef UNIFDEF_BLOCKS
131The
132.Fn scandir_b
133function appeared in Mac OS X 10.6.
134#endif