int stat(const char *file_name, struct stat *buf);
int fstat(int filedes, struct stat *buf);
int lstat(const char *file_name, struct stat *buf);
int stat_secure(const char *file_name, struct stat *buf, security_id_t *sid);
int fstat_secure(int filedes, struct stat *buf, security_id_t *sid);
int lstat_secure(const char *file_name, struct stat *buf, security_id_t *sid);
These functions return information about the specified file. You do not need any Unix access rights to the file to get this information but you need search rights to all directories named in the path leading to the file.
stat stats the file pointed to by file_name and fills in buf.
lstat is identical to stat, only the link itself is stated, not the file that is obtained by tracing the links.
fstat is identical to stat, only the open file pointed to by filedes (as returned by open(2)) is stated in place of file_name.
The stat_secure, fstat_secure, and lstat_secure functions may be used to obtain the SID of the file as well as its other attributes.
They all return a stat structure, which contains the following fields:
struct stat
{
dev_t st_dev; /* device */
ino_t st_ino; /* inode */
mode_t st_mode; /* protection */
nlink_t st_nlink; /* number of hard links */
uid_t st_uid; /* user ID of owner */
gid_t st_gid; /* group ID of owner */
dev_t st_rdev; /* device type (if inode device) */
off_t st_size; /* total size, in bytes */
unsigned long st_blksize; /* blocksize for filesystem I/O */
unsigned long st_blocks; /* number of blocks allocated */
time_t st_atime; /* time of last access */
time_t st_mtime; /* time of last modification */
time_t st_ctime; /* time of last change */
};
The value st_blocks gives the size of the file in 512-byte blocks. The value st_blksize gives the "preferred" blocksize for efficient file system I/O. (Writing to a file in smaller chunks may cause an inefficient read-modify-rewrite.)
Not all of the Linux filesystems implement all of the time fields. Traditionally, st_atime is changed by mknod(2), utime(2), read(2), write(2), and truncate(2).
Traditionally, st_mtime is changed by mknod(2), utime(2), and write(2). The st_mtime is not changed for changes in owner, group, hard link count, or mode.
Traditionally, st_ctime is changed by writing or by setting inode information (i.e., owner, group, link count, mode, etc.).
The following POSIX macros are defined to check the file type:
The following flags are defined for the st_mode field: