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All Rights Reserved. .\" Copyright (c) 2007, Sun Microsystems, Inc. All Rights Reserved. .\" .TH READDIR 3C "Jun 26, 2007" .SH NAME readdir, readdir_r \- read directory .SH SYNOPSIS .LP .nf #include #include \fBstruct dirent *\fR\fBreaddir\fR(\fBDIR *\fR\fIdirp\fR); .fi .LP .nf \fBstruct dirent *\fR\fBreaddir_r\fR(\fBDIR *\fR\fIdirp\fR, \fBstruct dirent *\fR\fIentry\fR); .fi .SS "Standard conforming" .LP .nf cc [ \fIflag\fR... ] \fIfile\fR... \fB-D_POSIX_PTHREAD_SEMANTICS\fR [ \fIlibrary\fR... ] \fBint\fR \fBreaddir_r\fR(\fBDIR *restrict\fR \fIdirp\fR, \fBstruct dirent *restrict\fR \fIentry\fR, \fBstruct dirent **restrict\fR \fIresult\fR); .fi .SH DESCRIPTION .sp .LP The type \fBDIR\fR, which is defined in the header <\fBdirent.h\fR>, represents a \fIdirectory stream\fR, which is an ordered sequence of all the directory entries in a particular directory. Directory entries represent files. Files can be removed from a directory or added to a directory asynchronously to the operation of \fBreaddir()\fR and \fBreaddir_r()\fR. .SS "\fBreaddir()\fR" .sp .LP The \fBreaddir()\fR function returns a pointer to a structure representing the directory entry at the current position in the directory stream specified by the argument \fIdirp\fR, and positions the directory stream at the next entry. It returns a null pointer upon reaching the end of the directory stream. The structure \fBdirent\fR defined by the \fB\fR header describes a directory entry. .sp .LP The \fBreaddir()\fR function will not return directory entries containing empty names. If entries for . (dot) or .. (dot-dot) exist, one entry will be returned for dot and one entry will be returned for dot-dot; otherwise they will not be returned. .sp .LP The pointer returned by \fBreaddir()\fR points to data that can be overwritten by another call to \fBreaddir()\fR on the same directory stream. These data are not overwritten by another call to \fBreaddir()\fR on a different directory stream. .sp .LP If a file is removed from or added to the directory after the most recent call to \fBopendir\fR(3C) or \fBrewinddir\fR(3C), whether a subsequent call to \fBreaddir()\fR returns an entry for that file is unspecified. .sp .LP The \fBreaddir()\fR function can buffer several directory entries per actual read operation. It marks for update the \fBst_atime\fR field of the directory each time the directory is actually read. .sp .LP After a call to \fBfork\fR(2), either the parent or child (but not both) can continue processing the directory stream using \fBreaddir()\fR, \fBrewinddir()\fR or \fBseekdir\fR(3C). If both the parent and child processes use these functions, the result is undefined. .sp .LP If the entry names a symbolic link, the value of the \fBd_ino\fR member is unspecified. .SS "\fBreaddir_r()\fR" .sp .LP Unless the end of the directory stream has been reached or an error occurred, the \fBreaddir_r()\fR function initializes the \fBdirent\fR structure referenced by \fBentry\fR to represent the directory entry at the current position in the directory stream referred to by \fIdirp\fR, and positions the directory stream at the next entry. .sp .LP The caller must allocate storage pointed to by \fIentry\fR to be large enough for a \fBdirent\fR structure with an array of \fBchar\fR \fBd_name\fR member containing at least \fBNAME_MAX\fR (that is, \fBpathconf(directory, _PC_NAME_MAX\fR)) plus one elements. (\fB_PC_NAME_MAX\fR is defined in <\fBunistd.h\fR>.) .sp .LP The \fBreaddir_r()\fR function will not return directory entries containing empty names. It is unspecified whether entries are returned for . (dot) or .. (dot-dot). .sp .LP If a file is removed from or added to the directory after the most recent call to \fBopendir()\fR or \fBrewinddir()\fR, whether a subsequent call to \fBreaddir_r()\fR returns an entry for that file is unspecified. .sp .LP The \fBreaddir_r()\fR function can buffer several directory entries per actual read operation. It marks for update the \fBst_atime\fR field of the directory each time the directory is actually read. .sp .LP The standard-conforming version (see \fBstandards\fR(5)) of the \fBreaddir_r()\fR function performs all of the actions described above and sets the pointer pointed to by \fIresult\fR. If a directory entry is returned, the pointer will be set to the same value as the \fIentry\fR argument; otherwise, it will be set to \fINULL\fR. .SH RETURN VALUES .sp .LP Upon successful completion, \fBreaddir()\fR and the default \fBreaddir_r()\fR return a pointer to an object of type \fBstruct dirent\fR. When an error is encountered, a null pointer is returned and \fBerrno\fR is set to indicate the error. When the end of the directory is encountered, a null pointer is returned and \fBerrno\fR is not changed. .sp .LP The standard-conforming \fBreaddir_r()\fR returns \fB0\fR if the end of the directory is encountered or a directory entry is stored in the structure referenced by \fIentry\fR. Otherwise, an error number is returned to indicate the failure. .SH ERRORS .sp .LP The \fBreaddir()\fR and \fBreaddir_r()\fR functions will fail if: .sp .ne 2 .na \fB\fBEOVERFLOW\fR\fR .ad .RS 13n One of the values in the structure to be returned cannot be represented correctly. .RE .sp .LP The \fBreaddir()\fR and \fBreaddir_r()\fR functions may fail if: .sp .ne 2 .na \fB\fBEBADF\fR\fR .ad .RS 10n The \fIdirp\fR argument does not refer to an open directory stream. .RE .sp .ne 2 .na \fB\fBENOENT\fR\fR .ad .RS 10n The current position of the directory stream is invalid. .RE .SH USAGE .sp .LP The \fBreaddir()\fR and \fBreaddir_r()\fR functions should be used in conjunction with \fBopendir()\fR, \fBclosedir()\fR, and \fBrewinddir()\fR to examine the contents of the directory. Since \fBreaddir()\fR and the default \fBreaddir_r()\fR return a null pointer both at the end of the directory and on error, an application wanting to check for error situations should set \fBerrno\fR to 0 before calling either of these functions. If \fBerrno\fR is set to non-zero on return, an error occurred. .sp .LP It is safe to use \fBreaddir()\fR in a threaded application, so long as only one thread reads from the directory stream at any given time. The \fBreaddir()\fR function is generally preferred over the \fBreaddir_r()\fR function. .sp .LP The standard-conforming \fBreaddir_r()\fR returns the error number if an error occurred. It returns 0 on success (including reaching the end of the directory stream). .sp .LP The \fBreaddir()\fR and \fBreaddir_r()\fR functions have transitional interfaces for 64-bit file offsets. See \fBlf64\fR(5). .SH EXAMPLES .LP \fBExample 1 \fRSearch the current directory for the entry \fIname\fR. .sp .LP The following sample program will search the current directory for each of the arguments supplied on the command line: .sp .in +2 .nf #include #include #include #include #include static void lookup(const char *arg) { DIR *dirp; struct dirent *dp; if ((dirp = opendir(".")) == NULL) { perror("couldn't open '.'"); return; } do { errno = 0; if ((dp = readdir(dirp)) != NULL) { if (strcmp(dp->d_name, arg) != 0) continue; (void) printf("found %s\en", arg); (void) closedir(dirp); return; } } while (dp != NULL); if (errno != 0) perror("error reading directory"); else (void) printf("failed to find %s\en", arg); (void) closedir(dirp); return; } int main(int argc, char *argv[]) { int i; for (i = 1; i < argc; i++) lookup(argv[i]); return (0); } .fi .in -2 .SH ATTRIBUTES .sp .LP See \fBattributes\fR(5) for descriptions of the following attributes: .sp .sp .TS box; c | c l | l . ATTRIBUTE TYPE ATTRIBUTE VALUE _ Interface Stability Standard _ MT-Level See below. .TE .sp .LP The \fBreaddir()\fR function is Unsafe. The \fBreaddir_r()\fR function is Safe. .SH SEE ALSO .sp .LP \fBfork\fR(2), \fBlstat\fR(2), \fBsymlink\fR(2), \fBIntro\fR(3), \fBclosedir\fR(3C), \fBopendir\fR(3C), \fBrewinddir\fR(3C), \fBscandir\fR(3C), \fBseekdir\fR(3C), \fBattributes\fR(5), \fBlf64\fR(5), \fBstandards\fR(5) .SH NOTES .sp .LP When compiling multithreaded programs, see the \fBMULTITHREADED APPLICATIONS\fR section of \fBIntro\fR(3). .sp .LP Solaris 2.4 and earlier releases provided a \fBreaddir_r()\fR interface as specified in POSIX.1c Draft 6. The final POSIX.1c standard changed the interface as described above. Support for the Draft 6 interface is provided for compatibility only and might not be supported in future releases. New applications and libraries should use the standard-conforming interface. .sp .LP For POSIX.1c-conforming applications, the \fB_POSIX_PTHREAD_SEMANTICS\fR and \fB_REENTRANT\fR flags are automatically turned on by defining the \fB_POSIX_C_SOURCE\fR flag with a value >= 199506L.