.\" $OpenBSD: opendir.3,v 1.3 2024/03/23 16:30:01 guenther Exp $ .\" .\" Copyright (c) 1983, 1991, 1993 .\" The Regents of the University of California. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .Dd $Mdocdate: March 23 2024 $ .Dt OPENDIR 3 .Os .Sh NAME .Nm opendir , .Nm fdopendir , .Nm readdir , .Nm readdir_r , .Nm telldir , .Nm seekdir , .Nm rewinddir , .Nm closedir , .Nm dirfd .Nd directory operations .Sh SYNOPSIS .In sys/types.h .In dirent.h .Ft DIR * .Fn opendir "const char *filename" .Ft DIR * .Fn fdopendir "int fd" .Ft struct dirent * .Fn readdir "DIR *dirp" .Ft int .Fn readdir_r "DIR *dirp" "struct dirent *entry" "struct dirent **result" .Ft long .Fn telldir "const DIR *dirp" .Ft void .Fn seekdir "DIR *dirp" "long loc" .Ft void .Fn rewinddir "DIR *dirp" .Ft int .Fn closedir "DIR *dirp" .Ft int .Fn dirfd "DIR *dirp" .Sh DESCRIPTION The .Fn opendir function opens the directory named by .Fa filename , associates a directory stream with it, and returns a pointer to be used to identify the directory stream in subsequent operations. On failure, .Dv NULL is returned and .Va errno is set to indicate the error. .Pp The .Fn fdopendir function is equivalent to .Fn opendir except that the directory is specified by file descriptor rather than by name. The file offset associated with the file descriptor at the time of the call determines which entries are returned. .Pp Upon successful return from .Fn fdopendir , the file descriptor is under the control of the system, and if any attempt is made to close the file descriptor or to modify the state of the associated directory, other than by means of .Fn closedir , .Fn readdir , .Fn readdir_r , or .Fn rewinddir , the behavior is undefined. Upon calling .Fn closedir the file descriptor shall be closed. .Pp The .Fn readdir function returns a pointer to the next directory entry in the named directory stream .Fa dirp . It returns .Dv NULL upon reaching the end of the directory or detecting an invalid .Fn seekdir operation. .Pp The .Fn readdir_r function is a deprecated variant of .Fn readdir . Like .Fn readdir , it initializes the .Vt dirent structure referenced by .Fa entry to represent the next directory entry in the named directory stream .Fa dirp , and stores a pointer to this structure at the location referenced by .Fa result . The storage pointed to by .Fa entry must be large enough for a dirent with a .Fa d_name array member containing at least .Dv NAME_MAX plus one elements. .Fn readdir_r returns 0 on success, or an error number if an error occurs; see .Sx ERRORS . On successful return, the pointer returned at .Fa "*result" will have the same value as the argument .Fa entry . Upon reaching the end of the directory stream, this pointer shall have the value .Dv NULL . .Pp The .Fn telldir function returns the current location associated with the named directory stream .Fa dirp . On failure, \-1 is returned and .Va errno is set to indicate the error. .Pp The .Fn seekdir function sets the position of the next .Fn readdir operation on the named directory stream .Fa dirp . The new position reverts to the one associated with the directory stream when the .Fn telldir operation was performed. Values returned by .Fn telldir are good only for the lifetime of the .Dv DIR pointer, .Fa dirp , from which they are derived. If the directory is closed and then reopened, the .Fn telldir value may be invalidated due to undetected directory compaction. .Pp The .Fn rewinddir function resets the position of the named directory stream .Fa dirp to the beginning of the directory. .Pp The .Fn closedir function closes the named directory stream and frees the structure associated with the .Fa dirp pointer, returning 0 on success. On failure, \-1 is returned and the global variable .Va errno is set to indicate the error. .Pp The .Fn dirfd function returns the integer file descriptor associated with the named directory stream .Fa dirp (see .Xr open 2 ) . .Sh EXAMPLES Sample code which searches a directory for entry .Dq name is: .Bd -literal -offset indent len = strlen(name); dirp = opendir("."); if (dirp) { while ((dp = readdir(dirp)) != NULL) if (dp->d_namlen == len && !strcmp(dp->d_name, name)) { closedir(dirp); return FOUND; } closedir(dirp); } return NOT_FOUND; .Ed .Sh ERRORS The .Fn opendir function will fail if: .Bl -tag -width Er .It Bq Er ENOTDIR The supplied .Fa filename is not a directory. .El .Pp The .Fn opendir function may also fail and set .Va errno for any of the errors specified for the routines .Xr fcntl 2 , .Xr fstat 2 , .Xr open 2 , and .Xr malloc 3 . .Pp The .Fn fdopendir function will fail if: .Bl -tag -width Er .It Bq Er EBADF The .Fa fd argument is not a valid file descriptor open for reading. .It Bq Er ENOTDIR The descriptor .Fa fd is not associated with a directory. .El .Pp The .Fn readdir and .Fn readdir_r functions may also fail and set .Va errno for any of the errors specified for the routine .Xr getdents 2 . .Pp The .Fn telldir function may also fail and set .Va errno for any of the errors specified for the routine .Xr realloc 3 . .Pp The .Fn closedir function may also fail and set .Va errno for any of the errors specified for the routine .Xr close 2 . .Sh SEE ALSO .Xr close 2 , .Xr getdents 2 , .Xr lseek 2 , .Xr open 2 , .Xr dir 5 .Sh STANDARDS The .Fn opendir , .Fn fdopendir , .Fn readdir , .Fn readdir_r , .Fn telldir , .Fn seekdir , .Fn rewinddir , .Fn closedir , and .Fn dirfd functions conform to .St -p1003.1-2008 . .Sh HISTORY The .Fn opendir , .Fn readdir , .Fn telldir , .Fn seekdir , .Fn rewinddir , .Fn closedir , and .Fn dirfd functions appeared in .Bx 4.2 . The .Fn fdopendir function appeared in .Ox 5.0 . .Sh CAVEATS The .Fn readdir_r function was intended to provide a thread-safe version of .Fn readdir . However, it was later found to be both unnecessary in the typical usage and unportable due to insufficient buffer sizing guidance. It was therefore officially deprecated in issue 8.