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);
These functions return information about the specified file. You do not need any 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 fopen(3) ) is stated in place of file_name.
They all return a stat structure, which is declared as follows:
struct stat
{
dev_t st_dev; /* device */
ino_t st_ino; /* inode */
umode_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 */
};
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 macros are defined to check the file type:
- S_ISLNK(m)
- is it a symbolic link?
- S_ISREG(m)
- regular file?
- S_ISDIR(m)
- directory?
- S_ISCHR(m)
- character device?
- S_ISBLK(m)
- block device?
- S_ISFIFO(m)
- fifo?
- S_ISSOCK(m)
- socket?
The following flags are defined for the st_mode field:
00001 others have execute permission
- S_IFMT
- 00170000 bitmask for the file type bitfields
- S_IFSOCK
- 0140000 socket
- S_IFLNK
- 0120000 symbolic link
- S_IFREG
- 0100000 regular file
- S_IFBLK
- 0060000 block device
- S_IFDIR
- 0040000 directory
- S_IFCHR
- 0020000 character device
- S_IFIFO
- 0010000 fifo
- S_ISUID
- 0004000 set UID bit
- S_ISGID
- 0002000 set GID bit
- S_ISVTX
- 0001000 sticky bit
- S_IRWXU
- 00700 user (file owner) has read, write and execute permission
- S_IRUSR (S_IREAD)
- 00400 user has read permission
- S_IWUSR (S_IWRITE)
- 00200 user has write permission
- S_IXUSR (S_IEXEC)
- 00100 user has execute permission
- S_IRWXG
- 00070 group has read, write and execute permission
- S_IRGRP
- 00040 group has read permission
- S_IWGRP
- 00020 group has write permission
- S_IXGRP
- 00010 group has execute permission
- S_IRWXO
- 00007 others have read, write and execute permission
- S_IROTH
- 00004 others have read permission
- S_IWOTH
- 00002 others have write permisson
- S_IXOTH