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Diffstat (limited to 'lib/libc/gen/directory.3')
| -rw-r--r-- | lib/libc/gen/directory.3 | 309 |
1 files changed, 309 insertions, 0 deletions
diff --git a/lib/libc/gen/directory.3 b/lib/libc/gen/directory.3 new file mode 100644 index 0000000000000..6fdb96ad97603 --- /dev/null +++ b/lib/libc/gen/directory.3 @@ -0,0 +1,309 @@ +.\" 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. +.\" +.\" @(#)directory.3 8.1 (Berkeley) 6/4/93 +.\" $FreeBSD$ +.\" +.Dd May 22, 2017 +.Dt DIRECTORY 3 +.Os +.Sh NAME +.Nm opendir , +.Nm fdopendir , +.Nm readdir , +.Nm readdir_r , +.Nm telldir , +.Nm seekdir , +.Nm rewinddir , +.Nm closedir , +.Nm fdclosedir , +.Nm dirfd +.Nd directory operations +.Sh LIBRARY +.Lb libc +.Sh SYNOPSIS +.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 "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 fdclosedir "DIR *dirp" +.Ft int +.Fn dirfd "DIR *dirp" +.Sh DESCRIPTION +.Bf -symbolic +The +.Fn readdir_r +interface is deprecated +because it cannot be used correctly unless +.Brq Va NAME_MAX +is a fixed value. +.Ef +.Pp +The +.Fn opendir +function +opens the directory named by +.Fa filename , +associates a +.Em directory stream +with it +and +returns a pointer to be used to identify the +.Em directory stream +in subsequent operations. +The pointer +.Dv NULL +is returned if +.Fa filename +cannot be accessed, or if it cannot +.Xr malloc 3 +enough memory to hold the whole thing. +.Pp +The +.Fn fdopendir +function is equivalent to the +.Fn opendir +function except that the directory is specified by a file descriptor +.Fa fd +rather than by a 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 description 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 is closed. +The +.Dv FD_CLOEXEC +flag is set on the file descriptor by a successful call to +.Fn fdopendir . +.Pp +The +.Fn readdir +function +returns a pointer to the next directory entry. +The directory entry remains valid until the next call to +.Fn readdir +or +.Fn closedir +on the same +.Em directory stream . +The function returns +.Dv NULL +upon reaching the end of the directory or on error. +In the event of an error, +.Va errno +may be set to any of the values documented for the +.Xr getdirentries 2 +system call. +.Pp +The +.Fn readdir_r +function +provides the same functionality as +.Fn readdir , +but the caller must provide a directory +.Fa entry +buffer to store the results in. +The buffer must be large enough for a +.Vt struct dirent +with a +.Va d_name +array with +.Brq Va NAME_MAX ++ 1 elements. +If the read succeeds, +.Fa result +is pointed at the +.Fa entry ; +upon reaching the end of the directory +.Fa result +is set to +.Dv NULL . +The +.Fn readdir_r +function +returns 0 on success or an error number to indicate failure. +.Pp +The +.Fn telldir +function +returns a token representing the current location associated with the named +.Em directory stream . +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, prior values returned by +.Fn telldir +will no longer be valid. +Values returned by +.Fn telldir +are also invalidated by a call to +.Fn rewinddir . +.Pp +The +.Fn seekdir +function +sets the position of the next +.Fn readdir +operation on the +.Em directory stream . +The new position reverts to the one associated with the +.Em directory stream +when the +.Fn telldir +operation was performed. +.Pp +The +.Fn rewinddir +function +resets the position of the named +.Em directory stream +to the beginning of the directory. +.Pp +The +.Fn closedir +function +closes the named +.Em 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 fdclosedir +function is equivalent to the +.Fn closedir +function except that this function returns directory file descriptor instead of +closing it. +.Pp +The +.Fn dirfd +function +returns the integer file descriptor associated with the named +.Em directory stream , +see +.Xr open 2 . +.Pp +Sample code which searches a directory for entry ``name'' is: +.Bd -literal -offset indent +dirp = opendir("."); +if (dirp == NULL) + return (ERROR); +len = strlen(name); +while ((dp = readdir(dirp)) != NULL) { + if (dp->d_namlen == len && strcmp(dp->d_name, name) == 0) { + (void)closedir(dirp); + return (FOUND); + } +} +(void)closedir(dirp); +return (NOT_FOUND); +.Ed +.Sh SEE ALSO +.Xr close 2 , +.Xr lseek 2 , +.Xr open 2 , +.Xr read 2 , +.Xr dir 5 +.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 +.Fx 8.0 . +.Fn fdclosedir +function appeared in +.Fx 10.0 . +.Sh BUGS +The behaviour of +.Fn telldir +and +.Fn seekdir +is likely to be wrong if there are parallel unlinks happening +and the directory is larger than one page. +There is code to ensure that a +.Fn seekdir +to the location given by a +.Fn telldir +immediately before the last +.Fn readdir +will always set the correct location to return the same value as that last +.Fn readdir +performed. +This is enough for some applications which want to +"push back the last entry read", e.g., Samba. +Seeks back to any other location, +other than the beginning of the directory, +may result in unexpected behaviour if deletes are present. +It is hoped that this situation will be resolved with changes to +.Fn getdirentries +and the VFS. |