What Do You Give Readdir for Path if You Want to Read Current Directoy
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Name
readdir, readdir_r - read directory
SYNOPSIS
#include <sys/types.h> #include <dirent.h> struct dirent * readdir(DIR * dirp);
struct dirent * readdir_r(DIR * dirp, struct dirent * entry);
Standard conforming
cc [ flag... ] file... -D_POSIX_PTHREAD_SEMANTICS [ library... ] int readdir_r(DIR *restrict dirp, struct dirent *restrict entry, struct dirent **restrict result);
DESCRIPTION
The type DIR, which is divers in the header <dirent.h>, represents a directory stream, which is an ordered sequence of all the directory entries in a particular directory. Directory entries stand for files. Files can be removed from a directory or added to a directory asynchronously to the operation of readdir() and readdir_r().
readdir()
The readdir() function returns a pointer to a structure representing the directory entry at the electric current position in the directory stream specified by the argument dirp, and positions the directory stream at the next entry. Information technology returns a null pointer upon reaching the finish of the directory stream. The structure dirent defined by the <dirent.h> header describes a directory entry.
The readdir() part will not return directory entries containing empty names. If entries for . (dot) or .. (dot-dot) exist, i entry volition be returned for dot and ane entry will be returned for dot-dot; otherwise they will not be returned.
The arrow returned by readdir() points to data that can exist overwritten by another call to readdir() on the same directory stream. These data are not overwritten by another call to readdir() on a different directory stream.
If a file is removed from or added to the directory afterwards the most recent call to opendir(3C) or rewinddir(3C), whether a subsequent call to readdir() returns an entry for that file is unspecified.
The readdir() office can buffer several directory entries per actual read functioning. It marks for update the st_atime field of the directory each time the directory is really read.
After a call to fork(2), either the parent or child (but not both) can go along processing the directory stream using readdir(), rewinddir() or seekdir(3C). If both the parent and child processes use these functions, the result is undefined.
If the entry names a symbolic link, the value of the d_ino member is unspecified.
readdir_r()
Unless the end of the directory stream has been reached or an error occurred, the readdir_r() function initializes the dirent construction referenced by entry to stand for the directory entry at the current position in the directory stream referred to past dirp, and positions the directory stream at the next entry.
The caller must classify storage pointed to past entry to be big plenty for a dirent structure with an array of char d_name fellow member containing at to the lowest degree NAME_MAX (that is, pathconf(directory, _PC_NAME_MAX)) plus one elements. (_PC_NAME_MAX is defined in <unistd.h>.)
The readdir_r() function will not return directory entries containing empty names. It is unspecified whether entries are returned for . (dot) or .. (dot-dot).
If a file is removed from or added to the directory after the virtually recent call to opendir() or rewinddir(), whether a subsequent call to readdir_r() returns an entry for that file is unspecified.
The readdir_r() function can buffer several directory entries per actual read performance. It marks for update the st_atime field of the directory each time the directory is actually read.
The standard-conforming version (come across standards(5)) of the readdir_r() function performs all of the actions described above and sets the pointer pointed to by result. If a directory entry is returned, the pointer will be prepare to the same value equally the entry argument; otherwise, it will be ready to Zilch.
Render VALUES
Upon successful completion, readdir() and the default readdir_r() return a pointer to an object of type struct dirent. When an fault is encountered, a null pointer is returned and errno is set to betoken the error. When the cease of the directory is encountered, a null arrow is returned and errno is not inverse.
The standard-conforming readdir_r() returns 0 if the cease of the directory is encountered or a directory entry is stored in the construction referenced by entry. Otherwise, an fault number is returned to indicate the failure.
ERRORS
The readdir() and readdir_r() functions will fail if:
EOVERFLOW
- One of the values in the structure to be returned cannot be represented correctly.
The readdir() and readdir_r() functions may fail if:
EBADF
- The dirp statement does not refer to an open directory stream.
ENOENT
- The current position of the directory stream is invalid.
USAGE
The readdir() and readdir_r() functions should be used in conjunction with opendir(), closedir(), and rewinddir() to examine the contents of the directory. Since readdir() and the default readdir_r() return a null arrow both at the end of the directory and on mistake, an application wanting to check for error situations should set errno to 0 before calling either of these functions. If errno is prepare to non-zero on return, an error occurred.
It is safe to use readdir() in a threaded awarding, so long as only one thread reads from the directory stream at any given time. The readdir() function is by and large preferred over the readdir_r() function.
The standard-conforming readdir_r() returns the mistake number if an fault occurred. It returns 0 on success (including reaching the end of the directory stream).
The readdir() and readdir_r() functions accept transitional interfaces for 64-bit file offsets. See lf64(5).
EXAMPLES
Example 1 Search the current directory for the entry name.
The following sample program will search the electric current directory for each of the arguments supplied on the command line:
#include <sys/types.h> #include <dirent.h> #include <errno.h> #include <stdio.h> #include <strings.h> static void lookup(const char *arg) { DIR *dirp; struct dirent *dp; if ((dirp = opendir(".")) == Naught) { perror("couldn't open '.'"); return; } do { errno = 0; if ((dp = readdir(dirp)) != NULL) { if (strcmp(dp->d_name, arg) != 0) continue; (void) printf("institute %south\due north", arg); (void) closedir(dirp); return; } } while (dp != NULL); if (errno != 0) perror("error reading directory"); else (void) printf("failed to notice %south\n", arg); (void) closedir(dirp); return; } int main(int argc, char *argv[]) { int i; for (i = ane; i < argc; i++) lookup(argv[i]); return (0); } ATTRIBUTES
Come across attributes(5) for descriptions of the post-obit attributes:
| ATTRIBUTE Type | Attribute VALUE |
| | |
| Interface Stability | Standard |
| | |
| MT-Level | |
The readdir() part is Unsafe. The readdir_r() function is Safe.
Run across Also
fork(2), lstat(two), symlink(two), Intro(3), closedir(3C), opendir(3C), rewinddir(3C), scandir(3C), seekdir(3C), attributes(5), lf64(5), standards(v)
NOTES
When compiling multithreaded programs, run into the MULTITHREADED APPLICATIONS department of Intro(iii).
Solaris 2.4 and before releases provided a readdir_r() interface equally specified in POSIX.1c Draft 6. The final POSIX.1c standard inverse the interface as described in a higher place. Back up for the Draft vi interface is provided for compatibility only and might not be supported in hereafter releases. New applications and libraries should use the standard-befitting interface.
For POSIX.1c-conforming applications, the _POSIX_PTHREAD_SEMANTICS and _REENTRANT flags are automatically turned on by defining the _POSIX_C_SOURCE flag with a value >= 199506L.
Index
- Proper noun
- SYNOPSIS
-
- Standard befitting
- DESCRIPTION
-
- readdir()
- readdir_r()
- Return VALUES
- ERRORS
- USAGE
- EXAMPLES
- ATTRIBUTES
- SEE ALSO
- NOTES
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