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Get the metadata/statistics for a file, directory or other file system item.

Syntax

#include <sys/stat.h>

int fstat (const char *filename, struct stat *st);

Parameters

• filename

  Path to the file to retrieve the stat structure for.

• st

  Pointer to a stat structure that will receive the information.

Return Value

The return value is null if successful. Otherwise, the return value is negative and errno is set:

• ENOENT

  No such file or directory.

• ENOSYS

  The system call is not supported for this file system, or not implemented.

Remarks

The stat structure is as follows:

struct stat
{
	dev_t st_dev;
	ino_t st_ino;
	mode_t st_mode;
	nlink_t st_nlink;
	uid_t st_uid;
	gid_t st_gid;
	dev_t st_rdev;
	off_t st_size;
	time_t st_atime;
	time_t st_mtime;
	time_t st_ctime;
	blksize_t st_blksize;
	blkcnt_t st_blocks;
};

Note that, being a microcontroller OS, most fields are left blank. The fields that will contain usable information are:

• st_mode

  Bitfield that may be accessed by the macros in the header file. The first part describes the type of file, and may be one of the following:

  • S_IFBLK: Block device. Typically disk drives.
  • S_IFCHR: Char device. Typically device drivers.
  • S_IFIFO: FIFO (pipe in our terminology).
  • S_IFREG: Regular file.
  • S_IFDIR: Directory.
  • S_IFLNK: Link.
  • S_IFSOCK: Network socket.

  The bitfield also contains the access rights of the file (read/write/exec permissions). The following definitions define the bits that are used:

  • S_IRUSR: Owner user read access.

  • S_IWUSR: Owner user write access.

  • S_IXUSR: Owner user execute access.

  • S_IRWXU: Bitwise or of the above three.

  • S_IRGRP: Group read access.

  • S_IWGRP: Group write access.

  • S_IXGRP: Group execute access.

  • S_IRWXG: Bitwise or of the above three.

  • S_IROTH: Anyone read access.

  • S_IWOTH: Anyone write access.

  • S_IXOTH: Anyone execute access.

  • S_IRWXO: Bitwise or of the above three.

  Note: At the time of writing, only the KFS care about the access rights. You may show the access rights of a file or directory contents with the ls -l command.

• st_size

  The size of the object in bytes. PipeFS will return the buffer size available to the pipe. Other special file systems may return a fixed size, depending on the characteristics of that file system.