5. Files and Directories Manager¶

5.1. Introduction¶

The files and directories manager is …

The directives provided by the files and directories manager are:

opendir - Open a Directory
readdir - Reads a directory
rewinddir - Resets the readdir() pointer
scandir - Scan a directory for matching entries
telldir - Return current location in directory stream
closedir - Ends directory read operation
getdents - Get directory entries
chdir - Changes the current working directory
fchdir - Changes the current working directory
getcwd - Gets current working directory
open - Opens a file
creat - Create a new file or rewrite an existing one
umask - Sets a file creation mask
link - Creates a link to a file
symlink - Creates a symbolic link to a file
readlink - Obtain the name of the link destination
mkdir - Makes a directory
mkfifo - Makes a FIFO special file
unlink - Removes a directory entry
rmdir - Delete a directory
rename - Renames a file
stat - Gets information about a file.
fstat - Gets file status
lstat - Gets file status
access - Check permissions for a file.
chmod - Changes file mode
fchmod - Changes permissions of a file
chown - Changes the owner and/ or group of a file
utime - Change access and/or modification times of an inode
ftruncate - Truncate a file to a specified length
truncate - Truncate a file to a specified length
pathconf - Gets configuration values for files
fpathconf - Get configuration values for files
mknod - Create a directory

5.2. Background¶

5.2.1. Path Name Evaluation¶

A pathname is a string that consists of no more than PATH_MAX bytes, including the terminating null character. A pathname has an optional beginning slash, followed by zero or more filenames separated by slashes. If the pathname refers to a directory, it may also have one or more trailing slashes. Multiple successive slahes are considered to be the same as one slash.

POSIX allows a pathname that begins with precisely two successive slashes to be interpreted in an implementation-defined manner. RTEMS does not currently recognize this as a special condition. Any number of successive slashes is treated the same as a single slash. POSIX requires that an implementation treat more than two leading slashes as a single slash.

5.3. Operations¶

There is currently no text in this section.

5.4. Directives¶

This section details the files and directories manager’s directives. A subsection is dedicated to each of this manager’s directives and describes the calling sequence, related constants, usage, and status codes.

5.4.1. opendir - Open a Directory¶

CALLING SEQUENCE:

#include <sys/types.h>
#include <dirent.h>
int opendir(
    const char *dirname
);

STATUS CODES:

`EACCES`	Search permission was denied on a component of the path prefix of `dirname`, or read permission is denied
`EMFILE`	Too many file descriptors in use by process
`ENFILE`	Too many files are currently open in the system.
`ENOENT`	Directory does not exist, or `name` is an empty string.
`ENOMEM`	Insufficient memory to complete the operation.
`ENOTDIR`	`name` is not a directory.

DESCRIPTION:

This routine opens a directory stream corresponding to the directory specified by the dirname argument. The directory stream is positioned at the first entry.

NOTES:

The routine is implemented in Cygnus newlib.

5.4.2. readdir - Reads a directory¶

CALLING SEQUENCE:

#include <sys/types.h>
#include <dirent.h>
    int readdir(
    DIR *dirp
);

STATUS CODES:

EBADF

Invalid file descriptor

DESCRIPTION:

The readdir() function returns a pointer to a structure dirent representing the next directory entry from the directory stream pointed to by dirp. On end-of-file, NULL is returned.

The readdir() function may (or may not) return entries for . or .. Your program should tolerate reading dot and dot-dot but not require them.

The data pointed to be readdir() may be overwritten by another call to readdir() for the same directory stream. It will not be overwritten by a call for another directory.

NOTES:

If ptr is not a pointer returned by malloc(), calloc(), or realloc() or has been deallocated with free() or realloc(), the results are not portable and are probably disastrous.

The routine is implemented in Cygnus newlib.

5.4.3. rewinddir - Resets the readdir() pointer¶

CALLING SEQUENCE:

#include <sys/types.h>
#include <dirent.h>
void rewinddir(
    DIR *dirp
);

STATUS CODES:

No value is returned.

DESCRIPTION:

The rewinddir() function resets the position associated with the directory stream pointed to by dirp. It also causes the directory stream to refer to the current state of the directory.

NOTES:

NONE

If dirp is not a pointer by opendir(), the results are undefined.

The routine is implemented in Cygnus newlib.

5.4.4. scandir - Scan a directory for matching entries¶

CALLING SEQUENCE:

#include <dirent.h>
int scandir(
    const char       *dir,
    struct dirent ***namelist,
    int  (*select)(const struct dirent *),
    int  (*compar)(const struct dirent **, const struct dirent **)
);

STATUS CODES:

ENOMEM

Insufficient memory to complete the operation.

DESCRIPTION:

The scandir() function scans the directory dir, calling select() on each directory entry. Entries for which select() returns non-zero are stored in strings allocated via malloc(), sorted using qsort() with the comparison function compar(), and collected in array namelist which is allocated via malloc(). If select is NULL, all entries are selected.

NOTES:

The routine is implemented in Cygnus newlib.

5.4.5. telldir - Return current location in directory stream¶

CALLING SEQUENCE:

#include <dirent.h>
off_t telldir(
    DIR *dir
);

STATUS CODES:

EBADF

Invalid directory stream descriptor dir.

DESCRIPTION:

The telldir() function returns the current location associated with the directory stream dir.

NOTES:

The routine is implemented in Cygnus newlib.

5.4.6. closedir - Ends directory read operation¶

CALLING SEQUENCE:

#include <sys/types.h>
#include <dirent.h>
int closedir(
    DIR *dirp
);

STATUS CODES:

EBADF

Invalid file descriptor

DESCRIPTION:

The directory stream associated with dirp is closed. The value in dirp may not be usable after a call to closedir().

NOTES:

NONE

The argument to closedir() must be a pointer returned by opendir(). If it is not, the results are not portable and most likely unpleasant.

The routine is implemented in Cygnus newlib.

5.4.7. chdir - Changes the current working directory¶

CALLING SEQUENCE:

#include <unistd.h>
int chdir(
    const char *path
);

STATUS CODES:

On error, this routine returns -1 and sets errno to one of the following:

`EACCES`	Search permission is denied for a directory in a file’s path prefix.
`ENAMETOOLONG`	Length of a filename string exceeds `PATH_MAX` and `_POSIX_NO_TRUNC` is in effect.
`ENOENT`	A file or directory does not exist.
`ENOTDIR`	A component of the specified pathname was not a directory when directory was expected.

DESCRIPTION:

The chdir() function causes the directory named by path to become the current working directory; that is, the starting point for searches of pathnames not beginning with a slash.

If chdir() detects an error, the current working directory is not changed.

NOTES:

NONE

5.4.8. fchdir - Changes the current working directory¶

CALLING SEQUENCE:

#include <unistd.h>
int fchdir(
    int fd
);

STATUS CODES:

On error, this routine returns -1 and sets errno to one of the following:

`EACCES`	Search permission is denied for a directory in a file’s path prefix.
`ENAMETOOLONG`	Length of a filename string exceeds `PATH_MAX` and `_POSIX_NO_TRUNC` is in effect.
`ENOENT`	A file or directory does not exist.
`ENOTDIR`	A component of the specified pathname was not a directory when directory was expected.

DESCRIPTION:

The fchdir() function causes the directory named by fd to become the current working directory; that is, the starting point for searches of pathnames not beginning with a slash.

If fchdir() detects an error, the current working directory is not changed.

NOTES:

NONE

5.4.9. getcwd - Gets current working directory¶

CALLING SEQUENCE:

#include <unistd.h>
int getcwd( void );

STATUS CODES:

`EINVAL`	Invalid argument
`ERANGE`	Result is too large
`EACCES`	Search permission is denied for a directory in a file’s path prefix.

DESCRIPTION:

The getcwd() function copies the absolute pathname of the current working directory to the character array pointed to by buf. The size argument is the number of bytes available in buf

NOTES:

There is no way to determine the maximum string length that fetcwd() may need to return. Applications should tolerate getting ERANGE and allocate a larger buffer.

It is possible for getcwd() to return EACCES if, say, login puts the process into a directory without read access.

The 1988 standard uses int instead of size_t for the second parameter.

5.4.10. open - Opens a file¶

CALLING SEQUENCE:

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
int open(
    const char *path,
    int         oflag,
    mode_t      mode
);

STATUS CODES:

`EACCES`	Search permission is denied for a directory in a file’s path prefix.
`EEXIST`	The named file already exists.
`EINTR`	Function was interrupted by a signal.
`EISDIR`	Attempt to open a directory for writing or to rename a file to be a directory.
`EMFILE`	Too many file descriptors are in use by this process.
`ENAMETOOLONG`	Length of a filename string exceeds `PATH_MAX` and `_POSIX_NO_TRUNC` is in effect.
`ENFILE`	Too many files are currently open in the system.
`ENOENT`	A file or directory does not exist.
`ENOSPC`	No space left on disk.
`ENOTDIR`	A component of the specified pathname was not a directory when a directory was expected.
`ENXIO`	No such device. This error may also occur when a device is not ready, for example, a tape drive is off-line.
`EROFS`	Read-only file system.

DESCRIPTION:

The open function establishes a connection between a file and a file descriptor. The file descriptor is a small integer that is used by I/O functions to reference the file. The path argument points to the pathname for the file.

The oflag argument is the bitwise inclusive OR of the values of symbolic constants. The programmer must specify exactly one of the following three symbols:

`O_RDONLY`	Open for reading only.
`O_WRONLY`	Open for writing only.
`O_RDWR`	Open for reading and writing.

Any combination of the following symbols may also be used.

`O_APPEND`	Set the file offset to the end-of-file prior to each write.
`O_CREAT`	If the file does not exist, allow it to be created. This flag indicates that the `mode` argument is present in the call to `open`.
`O_EXCL`	This flag may be used only if `O_CREAT` is also set. It causes the call to `open` to fail if the file already exists.
`O_NOCTTY`	Do not assign controlling terminal.
`O_NONBLOCK`	Do no wait for the device or file to be ready or available. After the file is open, the `read` and `write` calls return immediately. If the process would be delayed in the read or write opermation, -1 is returned and``errno`` is set to `EAGAIN` instead of blocking the caller.
`O_TRUNC`	This flag should be used only on ordinary files opened for writing. It causes the file to be tuncated to zero length..

Upon successful completion, open returns a non-negative file descriptor.

NOTES:

NONE

5.4.11. creat - Create a new file or rewrite an existing one¶

CALLING SEQUENCE:

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
int creat(
    const char *path,
    mode_t      mode
);

STATUS CODES:

`EEXIST`	`path` already exists and `O_CREAT` and `O_EXCL` were used.
`EISDIR`	`path` refers to a directory and the access requested involved writing
`ETXTBSY`	`path` refers to an executable image which is currently being executed and write access was requested
`EFAULT`	`path` points outside your accessible address space
`EACCES`	The requested access to the file is not allowed, or one of the directories in `path` did not allow search (execute) permission.
`ENAMETOOLONG`	`path` was too long.
`ENOENT`	A directory component in `path` does not exist or is a dangling symbolic link.
`ENOTDIR`	A component used as a directory in `path` is not, in fact, a directory.
`EMFILE`	The process alreadyh has the maximum number of files open.
`ENFILE`	The limit on the total number of files open on the system has been reached.
`ENOMEM`	Insufficient kernel memory was available.
`EROFS`	`path` refers to a file on a read-only filesystem and write access was requested

DESCRIPTION:

creat attempts to create a file and return a file descriptor for use in read, write, etc.

NOTES:

NONE

The routine is implemented in Cygnus newlib.

5.4.12. umask - Sets a file creation mask.¶

CALLING SEQUENCE:

#include <sys/types.h>
#include <sys/stat.h>
mode_t umask(
    mode_t cmask
);

STATUS CODES:

DESCRIPTION:

The umask() function sets the process file creation mask to cmask. The file creation mask is used during open(), creat(), mkdir(), mkfifo() calls to turn off permission bits in the mode argument. Bit positions that are set in cmask are cleared in the mode of the created file.

NOTES:

NONE

The cmask argument should have only permission bits set. All other bits should be zero.

In a system which supports multiple processes, the file creation mask is inherited across fork() and exec() calls. This makes it possible to alter the default permission bits of created files. RTEMS does not support multiple processes so this behavior is not possible.

5.4.13. link - Creates a link to a file¶

CALLING SEQUENCE:

#include <unistd.h>
int link(
    const char *existing,
    const char *new
);

STATUS CODES:

`EACCES`	Search permission is denied for a directory in a file’s path prefix
`EEXIST`	The named file already exists.
`EMLINK`	The number of links would exceed `LINK_MAX`.
`ENAMETOOLONG`	Length of a filename string exceeds `PATH_MAX` and `_POSIX_NO_TRUNC` is in effect.
`ENOENT`	A file or directory does not exist.
`ENOSPC`	No space left on disk.
`ENOTDIR`	A component of the specified pathname was not a directory when a directory was expected.
`EPERM`	Operation is not permitted. Process does not have the appropriate priviledges or permissions to perform the requested operations.
`EROFS`	Read-only file system.
`EXDEV`	Attempt to link a file to another file system.

DESCRIPTION:

The link() function atomically creates a new link for an existing file and increments the link count for the file.

If the link() function fails, no directories are modified.

The existing argument should not be a directory.

The caller may (or may not) need permission to access the existing file.

NOTES:

NONE

5.4.14. symlink - Creates a symbolic link to a file¶

CALLING SEQUENCE:

#include <unistd.h>
int symlink(
    const char *topath,
    const char *frompath
);

STATUS CODES:

`EACCES`	Search permission is denied for a directory in a file’s path prefix
`EEXIST`	The named file already exists.
`ENAMETOOLONG`	Length of a filename string exceeds `PATH_MAX` and `_POSIX_NO_TRUNC` is in effect.
`ENOENT`	A file or directory does not exist.
`ENOSPC`	No space left on disk.
`ENOTDIR`	A component of the specified pathname was not a directory when a directory was expected.
`EPERM`	Operation is not permitted. Process does not have the appropriate priviledges or permissions to perform the requested operations.
`EROFS`	Read-only file system.

DESCRIPTION:

The symlink() function creates a symbolic link from the frombath to the topath. The symbolic link will be interpreted at run-time.

If the symlink() function fails, no directories are modified.

The caller may (or may not) need permission to access the existing file.

NOTES:

NONE

5.4.15. readlink - Obtain the name of a symbolic link destination¶

CALLING SEQUENCE:

#include <unistd.h>
int readlink(
    const char *path,
    char       *buf,
    size_t      bufsize
);

STATUS CODES:

`EACCES`	Search permission is denied for a directory in a file’s path prefix
`ENAMETOOLONG`	Length of a filename string exceeds `PATH_MAX` and `_POSIX_NO_TRUNC` is in effect.
`ENOENT`	A file or directory does not exist.
`ENOTDIR`	A component of the prefix pathname was not a directory when a directory was expected.
`ELOOP`	Too many symbolic links were encountered in the pathname.
`EINVAL`	The pathname does not refer to a symbolic link
`EFAULT`	An invalid pointer was passed into the `readlink()` routine.

DESCRIPTION:

The readlink() function places the symbolic link destination into buf argument and returns the number of characters copied.

If the symbolic link destination is longer than bufsize characters the name will be truncated.

NOTES:

NONE

5.4.16. mkdir - Makes a directory¶

CALLING SEQUENCE:

#include <sys/types.h>
#include <sys/stat.h>
int mkdir(
    const char *path,
    mode_t      mode
);

STATUS CODES:

`EACCES`	Search permission is denied for a directory in a file’s path prefix
`EEXIST`	The name file already exist.
`EMLINK`	The number of links would exceed `LINK_MAX`
`ENAMETOOLONG`	Length of a filename string exceeds `PATH_MAX` and `_POSIX_NO_TRUNC` is in effect.
`ENOENT`	A file or directory does not exist.
`ENOSPC`	No space left on disk.
`ENOTDIR`	A component of the specified pathname was not a directory when a directory was expected.
`EROFS`	Read-only file system.

DESCRIPTION:

The mkdir() function creates a new diectory named path. The permission bits (modified by the file creation mask) are set from mode. The owner and group IDs for the directory are set from the effective user ID and group ID.

The new directory may (or may not) contain entries for . and .. but is otherwise empty.

NOTES:

NONE

5.4.17. mkfifo - Makes a FIFO special file¶

CALLING SEQUENCE:

#include <sys/types.h>
#include <sys/stat.h>
int mkfifo(
    const char *path,
    mode_t      mode
);

STATUS CODES:

`EACCES`	Search permission is denied for a directory in a file’s path prefix
`EEXIST`	The named file already exists.
`ENOENT`	A file or directory does not exist.
`ENOSPC`	No space left on disk.
`ENOTDIR`	A component of the specified `path` was not a directory when a directory was expected.
`EROFS`	Read-only file system.

DESCRIPTION:

The mkfifo() function creates a new FIFO special file named path. The permission bits (modified by the file creation mask) are set from mode. The owner and group IDs for the FIFO are set from the efective user ID and group ID.

NOTES:

NONE

5.4.18. unlink - Removes a directory entry¶

CALLING SEQUENCE:

#include <unistd.h>
int unlink(
    const char path
);

STATUS CODES:

`EACCES`	Search permission is denied for a directory in a file’s path prefix
`EBUSY`	The directory is in use.
`ENAMETOOLONG`	Length of a filename string exceeds `PATH_MAX` and `_POSIX_NO_TRUNC` is in effect.
`ENOENT`	A file or directory does not exist.
`ENOTDIR`	A component of the specified `path` was not a directory when a directory was expected.
`EPERM`	Operation is not permitted. Process does not have the appropriate priviledges or permissions to perform the requested operations.
`EROFS`	Read-only file system.

DESCRIPTION:

The unlink function removes the link named by path and decrements the link count of the file referenced by the link. When the link count goes to zero and no process has the file open, the space occupied by the file is freed and the file is no longer accessible.

NOTES:

NONE

5.4.19. rmdir - Delete a directory¶

CALLING SEQUENCE:

#include <unistd.h>
int rmdir(
    const char *pathname
);

STATUS CODES:

`EPERM`	The filesystem containing `pathname` does not support the removal of directories.
`EFAULT`	`pathname` points ouside your accessible address space.
`EACCES`	Write access to the directory containing `pathname` was not allowed for the process’s effective uid, or one of the directories in``pathname`` did not allow search (execute) permission.
`EPERM`	The directory containing `pathname` has the stickybit (S_ISVTX) set and the process’s effective uid is neither the uid of the file to be delected nor that of the director containing it.
`ENAMETOOLONG`	`pathname` was too long.
`ENOENT`	A dirctory component in `pathname` does not exist or is a dangling symbolic link.
`ENOTDIR`	`pathname`, or a component used as a directory in `pathname`, is not, in fact, a directory.
`ENOTEMPTY`	`pathname` contains entries other than . and .. .
`EBUSY`	`pathname` is the current working directory or root directory of some process
`EBUSY`	`pathname` is the current directory or root directory of some process.
`ENOMEM`	Insufficient kernel memory was available
`EROGS`	`pathname` refers to a file on a read-only filesystem.
`ELOOP`	`pathname` contains a reference to a circular symbolic link

DESCRIPTION:

rmdir deletes a directory, which must be empty

NOTES:

NONE

5.4.20. rename - Renames a file¶

CALLING SEQUENCE:

#include <unistd.h>
int rename(
    const char *old,
    const char *new
);

STATUS CODES:

`EACCES`	Search permission is denied for a directory in a file’s path prefix.
`EBUSY`	The directory is in use.
`EEXIST`	The named file already exists.
`EINVAL`	Invalid argument.
`EISDIR`	Attempt to open a directory for writing or to rename a file to be a directory.
`EMLINK`	The number of links would exceed `LINK_MAX`.
`ENAMETOOLONG`	Length of a filename string exceeds `PATH_MAX` and `_POSIX_NO_TRUNC` is in effect.
`ENOENT`	A file or directory does no exist.
`ENOSPC`	No space left on disk.
`ENOTDIR`	A component of the specified pathname was not a directory when a directory was expected.
`ENOTEMPTY`	Attempt to delete or rename a non-empty directory.
`EROFS`	Read-only file system
`EXDEV`	Attempt to link a file to another file system.

DESCRIPTION:

The rename() function causes the file known bo old to now be known as new.

Ordinary files may be renamed to ordinary files, and directories may be renamed to directories; however, files cannot be converted using rename(). The new pathname may not contain a path prefix of old.

NOTES:

If a file already exists by the name new, it is removed. The rename() function is atomic. If the rename() detects an error, no files are removed. This guarantees that the rename("x", "x") does not remove x.

You may not rename dot or dot-dot.

The routine is implemented in Cygnus newlib using link() and unlink().

5.4.21. stat - Gets information about a file¶

CALLING SEQUENCE:

#include <sys/types.h>
#include <sys/stat.h>
int stat(
    const char  *path,
    struct stat *buf
);

STATUS CODES:

`EACCES`	Search permission is denied for a directory in a file’s path prefix.
`EBADF`	Invalid file descriptor.
`ENAMETOOLONG`	Length of a filename string exceeds `PATH_MAX` and `_POSIX_NO_TRUNC` is in effect.
`ENOENT`	A file or directory does not exist.
`ENOTDIR`	A component of the specified pathname was not a directory when a directory was expected.

DESCRIPTION:

The path argument points to a pathname for a file. Read, write, or execute permission for the file is not required, but all directories listed in path must be searchable. The stat() function obtains information about the named file and writes it to the area pointed to by buf.

NOTES:

NONE

5.4.22. fstat - Gets file status¶

CALLING SEQUENCE:

#include <sys/types.h>
#include <sys/stat.h>
int fstat(
    int          fildes,
    struct stat *buf
);

STATUS CODES:

EBADF

Invalid file descriptor

DESCRIPTION:

The fstat() function obtains information about the file associated with fildes and writes it to the area pointed to by the buf argument.

NOTES:

If the filesystem object referred to by fildes is a link, then the information returned in buf refers to the destination of that link. This is in contrast to lstat() which does not follow the link.

5.4.23. lstat - Gets file status¶

CALLING SEQUENCE:

#include <sys/types.h>
#include <sys/stat.h>
int lstat(
    int          fildes,
    struct stat *buf
);

STATUS CODES:

EBADF

Invalid file descriptor

DESCRIPTION:

The lstat() function obtains information about the file associated with fildes and writes it to the area pointed to by the buf argument.

NOTES:

If the filesystem object referred to by fildes is a link, then the information returned in buf refers to the link itself. This is in contrast to fstat() which follows the link.

The lstat() routine is defined by BSD 4.3 and SVR4 and not included in POSIX 1003.1b-1996.

5.4.24. access - Check permissions for a file¶

CALLING SEQUENCE:

#include <unistd.h>
int access(
    const char *pathname,
    int         mode
);

STATUS CODES:

`EACCES`	The requested access would be denied, either to the file itself or one of the directories in `pathname`.
`EFAULT`	`pathname` points outside your accessible address space.
`EINVAL`	`Mode` was incorrectly specified.
`ENAMETOOLONG`	`pathname` is too long.
`ENOENT`	A directory component in `pathname` would have been accessible but does not exist or was a dangling symbolic link.
`ENOTDIR`	A component used as a directory in `pathname` is not, in fact, a directory.
`ENOMEM`	Insufficient kernel memory was available.

DESCRIPTION:

Access checks whether the process would be allowed to read, write or test for existence of the file (or other file system object) whose name is pathname. If pathname is a symbolic link permissions of the file referred by this symbolic link are tested.

Mode is a mask consisting of one or more of R_OK, W_OK, X_OK and F_OK.

NOTES:

NONE

5.4.25. chmod - Changes file mode.¶

CALLING SEQUENCE:

#include <sys/types.h>
#include <sys/stat.h>
int chmod(
    const char *path,
    mode_t      mode
);

STATUS CODES:

`EACCES`	Search permission is denied for a directory in a file’s path prefix
`ENAMETOOLONG`	Length of a filename string exceeds `PATH_MAX` and `_POSIX_NO_TRUNC` is in effect.
`ENOENT`	A file or directory does not exist.
`ENOTDIR`	A component of the specified pathname was not a directory when a directory was expected.
`EPERM`	Operation is not permitted. Process does not have the appropriate priviledges or permissions to perform the requested operations.
`EROFS`	Read-only file system.

DESCRIPTION:

Set the file permission bits, the set user ID bit, and the set group ID bit for the file named by path to mode. If the effective user ID does not match the owner of the file and the calling process does not have the appropriate privileges, chmod() returns -1 and sets errno to EPERM.

NOTES:

NONE

5.4.26. fchmod - Changes permissions of a file¶

CALLING SEQUENCE:

#include <sys/types.h>
#include <sys/stat.h>
int fchmod(
    int    fildes,
    mode_t mode
);

STATUS CODES:

`EACCES`	Search permission is denied for a directory in a file’s path prefix.
`EBADF`	The descriptor is not valid.
`EFAULT`	`path` points outside your accessible address space.
`EIO`	A low-level I/o error occurred while modifying the inode.
`ELOOP`	`path` contains a circular reference
`ENAMETOOLONG`	Length of a filename string exceeds `PATH_MAX` and `_POSIX_NO_TRUNC` is in effect.
`ENOENT`	A file or directory does no exist.
`ENOMEM`	Insufficient kernel memory was avaliable.
`ENOTDIR`	A component of the specified pathname was not a directory when a directory was expected.
`EPERM`	The effective UID does not match the owner of the file, and is not zero
`EROFS`	Read-only file system

DESCRIPTION:

The mode of the file given by path or referenced by filedes is changed.

NOTES:

NONE

5.4.27. getdents - Get directory entries¶

CALLING SEQUENCE:

#include <unistd.h>
#include <linux/dirent.h>
#include <linux/unistd.h>
long getdents(
    int   dd_fd,
    char *dd_buf,
    int   dd_len
);

STATUS CODES:

A successful call to getdents returns th the number of bytes read. On end of directory, 0 is returned. When an error occurs, -1 is returned, and errno is set appropriately.

`EBADF`	Invalid file descriptor `fd`.
`EFAULT`	Argument points outside the calling process’s address space.
`EINVAL`	Result buffer is too small.
`ENOENT`	No such directory.
`ENOTDIR`	File descriptor does not refer to a directory.

DESCRIPTION:

getdents reads several dirent structures from the directory pointed by fd into the memory area pointed to by dirp. The parameter count is the size of the memory area.

NOTES:

NONE

5.4.28. chown - Changes the owner and/or group of a file.¶

CALLING SEQUENCE:

#include <sys/types.h>
#include <unistd.h>
int chown(
    const char *path,
    uid_t       owner,
    gid_t       group
);

STATUS CODES:

`EACCES`	Search permission is denied for a directory in a file’s path prefix
`EINVAL`	Invalid argument
`ENAMETOOLONG`	Length of a filename string exceeds `PATH_MAX` and `_POSIX_NO_TRUNC` is in effect.
`ENOENT`	A file or directory does not exist.
`ENOTDIR`	A component of the specified pathname was not a directory when a directory was expected.
`EPERM`	Operation is not permitted. Process does not have the appropriate priviledges or permissions to perform the requested operations.
`EROFS`	Read-only file system.

DESCRIPTION:

The user ID and group ID of the file named by path are set to owner and path, respectively.

For regular files, the set group ID (S_ISGID) and set user ID (S_ISUID) bits are cleared.

Some systems consider it a security violation to allow the owner of a file to be changed, If users are billed for disk space usage, loaning a file to another user could result in incorrect billing. The chown() function may be restricted to privileged users for some or all files. The group ID can still be changed to one of the supplementary group IDs.

NOTES:

This function may be restricted for some file. The pathconf function can be used to test the _PC_CHOWN_RESTRICTED flag.

5.4.29. utime - Change access and/or modification times of an inode¶

CALLING SEQUENCE:

#include <sys/types.h>
int utime(
    const char     *filename,
    struct utimbuf *buf
);

STATUS CODES:

`EACCES`	Permission to write the file is denied
`ENOENT`	`Filename` does not exist

DESCRIPTION:

Utime changes the access and modification times of the inode specified by filename to the actime and modtime fields of buf respectively. If buf is NULL, then the access and modification times of the file are set to the current time.

NOTES:

NONE

5.4.30. ftruncate - truncate a file to a specified length¶

CALLING SEQUENCE:

#include <unistd.h>
int ftrunctate(
    int    fd,
    size_t length
);

STATUS CODES:

`ENOTDIR`	A component of the path prefix is not a directory.
`EINVAL`	The pathname contains a character with the high-order bit set.
`ENAMETOOLONG`	The length of the specified pathname exceeds `PATH_MAX` bytes, or the length of a component of the pathname exceeds `NAME_MAX` bytes.
`ENOENT`	The named file does not exist.
`EACCES`	The named file is not writable by the user.
`EACCES`	Search permission is denied for a component of the path prefix.
`ELOOP`	Too many symbolic links were encountered in translating the pathname
`EISDIR`	The named file is a directory.
`EROFS`	The named file resides on a read-only file system
`ETXTBSY`	The file is a pure procedure (shared text) file that is being executed
`EIO`	An I/O error occurred updating the inode.
`EFAULT`	`Path` points outside the process’s allocated address space.
`EBADF`	The `fd` is not a valid descriptor.

DESCRIPTION:

truncate() causes the file named by path or referenced by fd to be truncated to at most length bytes in size. If the file previously was larger than this size, the extra data is lost. With ftruncate(), the file must be open for writing.

NOTES:

NONE

5.4.31. truncate - truncate a file to a specified length¶

CALLING SEQUENCE:

#include <unistd.h>
int trunctate(
    const char *path,
    size_t      length
);

STATUS CODES:

`ENOTDIR`	A component of the path prefix is not a directory.
`EINVAL`	The pathname contains a character with the high-order bit set.
`ENAMETOOLONG`	The length of the specified pathname exceeds `PATH_MAX` bytes, or the length of a component of the pathname exceeds `NAME_MAX` bytes.
`ENOENT`	The named file does not exist.
`EACCES`	The named file is not writable by the user.
`EACCES`	Search permission is denied for a component of the path prefix.
`ELOOP`	Too many symbolic links were encountered in translating the pathname
`EISDIR`	The named file is a directory.
`EROFS`	The named file resides on a read-only file system
`ETXTBSY`	The file is a pure procedure (shared text) file that is being executed
`EIO`	An I/O error occurred updating the inode.
`EFAULT`	`Path` points outside the process’s allocated address space.
`EBADF`	The `fd` is not a valid descriptor.

DESCRIPTION:

truncate() causes the file named by path or referenced by``fd`` to be truncated to at most length bytes in size. If the file previously was larger than this size, the extra data is lost. With ftruncate(), the file must be open for writing.

NOTES:

NONE

5.4.32. pathconf - Gets configuration values for files¶

CALLING SEQUENCE:

#include <unistd.h>
int pathconf(
    const char *path,
    int         name
);

STATUS CODES:

`EINVAL`	Invalid argument
`EACCES`	Permission to write the file is denied
`ENAMETOOLONG`	Length of a filename string exceeds `PATH_MAX` and `_POSIX_NO_TRUNC` is in effect.
`ENOENT`	A file or directory does not exist
`ENOTDIR`	A component of the specified `path` was not a directory whan a directory was expected.

DESCRIPTION:

pathconf() gets a value for the configuration option name for the open file descriptor filedes.

The possible values for name are:

`_PC_LINK_MAX`	Returns the maximum number of links to the file. If `filedes` or``path`` refer to a directory, then the value applies to the whole directory. The corresponding macro is `_POSIX_LINK_MAX`.
`_PC_MAX_CANON`	Returns the maximum length of a formatted input line, where `filedes` or `path` must refer to a terminal. The corresponding macro is `_POSIX_MAX_CANON`.
`_PC_MAX_INPUT`	Returns the maximum length of an input line, where `filedes` or `path` must refer to a terminal. The corresponding macro is``_POSIX_MAX_INPUT``.
`_PC_NAME_MAX`	Returns the maximum length of a filename in the directory `path` or `filedes`. The process is allowed to create. The corresponding macro is `_POSIX_NAME_MAX`.
`_PC_PATH_MAX`	returns the maximum length of a relative pathname when `path` or``filedes`` is the current working directory. The corresponding macro is `_POSIX_PATH_MAX`.
`_PC_PIPE_BUF`	returns the size of the pipe buffer, where `filedes` must refer to a pipe or FIFO and `path` must refer to a FIFO. The corresponding macro is `_POSIX_PIPE_BUF`.
`_PC_CHOWN_RESTRICTED`	Returns nonzero if the `chown(2)` call may not be used on this file. If``filedes`` or `path` refer to a directory, then this applies to all files in that directory. The corresponding macro is `_POSIX_CHOWN_RESTRICTED`.

NOTES:

Files with name lengths longer than the value returned for name equal _PC_NAME_MAX may exist in the given directory.

5.4.33. fpathconf - Gets configuration values for files¶

CALLING SEQUENCE:

#include <unistd.h>
int fpathconf(
    int filedes,
    int name
);

STATUS CODES:

`EINVAL`	Invalid argument
`EACCES`	Permission to write the file is denied
`ENAMETOOLONG`	Length of a filename string exceeds `PATH_MAX` and `_POSIX_NO_TRUNC` is in effect.
`ENOENT`	A file or directory does not exist
`ENOTDIR`	A component of the specified `path` was not a directory whan a directory was expected.

DESCRIPTION:

pathconf() gets a value for the configuration option name for the open file descriptor filedes.

The possible values for name are:

`_PC_LINK_MAX`	Returns the maximum number of links to the file. If `filedes` or `path` refer to a directory, then the value applies to the whole directory. The corresponding macro is `_POSIX_LINK_MAX`.
`_PC_MAX_CANON`	returns the maximum length of a formatted input line, where `filedes` or `path` must refer to a terminal. The corresponding macro is `_POSIX_MAX_CANON`.
`_PC_MAX_INPUT`	Returns the maximum length of an input line, where `filedes` or `path` must refer to a terminal. The corresponding macro is `_POSIX_MAX_INPUT`.
`_PC_NAME_MAX`	Returns the maximum length of a filename in the directory `path` or `filedes`. The process is allowed to create. The corresponding macro is `_POSIX_NAME_MAX`.
`_PC_PATH_MAX`	Returns the maximum length of a relative pathname when `path` or `filedes` is the current working directory. The corresponding macro is `_POSIX_PATH_MAX`.
`_PC_PIPE_BUF`	Returns the size of the pipe buffer, where `filedes` must refer to a pipe or FIFO and `path` must refer to a FIFO. The corresponding macro is `_POSIX_PIPE_BUF`.
`_PC_CHOWN_RESTRICTED`	Returns nonzero if the `chown()` call may not be used on this file. If `filedes` or `path` refer to a directory, then this applies to all files in that directory. The corresponding macro is `_POSIX_CHOWN_RESTRICTED`.

NOTES:

NONE

5.4.34. mknod - create a directory¶

CALLING SEQUENCE:

#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
long mknod(
    const char *pathname,
    mode_t      mode,
    dev_t       dev
);

STATUS CODES:

mknod returns zero on success, or -1 if an error occurred (in which case, errno is set appropriately).

`ENAMETOOLONG`	`pathname` was too long.
`ENOENT`	A directory component in `pathname` does not exist or is a dangling symbolic link.
`ENOTDIR`	A component used in the directory `pathname` is not, in fact, a directory.
`ENOMEM`	Insufficient kernel memory was available
`EROFS`	`pathname` refers to a file on a read-only filesystem.
`ELOOP`	`pathname` contains a reference to a circular symbolic link, ie a symbolic link whose expansion contains a reference to itself.
`ENOSPC`	The device containing `pathname` has no room for the new node.

DESCRIPTION:

mknod attempts to create a filesystem node (file, device special file or named pipe) named pathname, specified by mode and dev.

mode specifies both the permissions to use and the type of node to be created.

It should be a combination (using bitwise OR) of one of the file types listed below and the permissions for the new node.

The permissions are modified by the process’s umask in the usual way: the permissions of the created node are (mode & ~umask).

The file type should be one of S_IFREG, S_IFCHR, S_IFBLK and S_IFIFO to specify a normal file (which will be created empty), character special file, block special file or FIFO (named pipe), respectively, or zero, which will create a normal file.

If the file type is S_IFCHR or S_IFBLK then dev specifies the major and minor numbers of the newly created device special file; otherwise it is ignored.

The newly created node will be owned by the effective uid of the process. If the directory containing the node has the set group id bit set, or if the filesystem is mounted with BSD group semantics, the new node will inherit the group ownership from its parent directory; otherwise it will be owned by the effective gid of the process.

NOTES:

NONE