STAT(2)
NAME
stat, lstat, fstat − get file status
USAGE
#include <sys/types.h> #include <sys/stat.h>
stat(path, buf) char *path; struct stat *buf;
lstat(path, buf) char *path; struct stat *buf;
fstat(fd, buf) int fd; struct stat *buf;
DESCRIPTION
Stat obtains information about the file path. Read, write, or execute permission of the named file is not required, but all directories listed in the pathname leading to the file must be traversable.
Lstat is like stat, except in the case where the named file is a symbolic link. In this case, lstat returns information about the link, while stat returns information about the file to which the link refers.
Fstat obtains the same information about the open file to which fd refers (similar to the information returned by an open call).
In all cases, buf is a pointer to a stat structure into which information about the file is placed. The contents of this structure are:
struct stat { dev_tst_dev; /* device inode resides on */ ino_t st_ino; /* this inode’s number */ u_short st_mode; /* protection */ short st_nlink; /* number or hard links to the file */ short st_uid; /* user-id of owner */ short st_gid; /* group-id of owner */ dev_t st_rdev; /* the device type, for inode that is device */ off_t st_size; /* total size of file */ time_t st_atime; /* file last access time */ int st_spare1; time_t st_mtime; /* file last modify time */ int st_spare2; time_t st_ctime; /* file last status change time */ int st_spare3; long st_blksize; /* optimal blocksize for file system i/o ops */ long st_blocks; /* actual number of blocks allocated */ long st_spare4[2];
};
st_atime Time when file data was last read or modified. Changed by the following system calls: mknod(2), utimes(2), read(2), and write(2). For reasons of efficiency, st_atime is not set when a directory is searched.
st_mtime Time when data was last modified. It is not set by changes of owner, group, link count, or mode. Changed by the following system calls: mknod(2), utimes(2), write(2).
st_ctime Time when file status was last changed. It is set both both by writing and changing the i-node. Changed by the following system calls: chmod(2) chown(2), link(2), mknod(2), unlink(2), utimes(2), write(2).
The status information word st_mode has bits: #define S_IFMT0170000/* type of file */ #define S_IFDIR 0040000 /* directory */ #define S_IFCHR 0020000 /* character special */ #define S_IFBLK 0060000 /* block special */ #define S_IFREG 0100000 /* regular */ #define S_IFLNK 0120000 /* symbolic link */ #define S_IFSOCK 0140000 /* socket */ #define S_ISUID 0004000 /* set user id on execution */ #define S_ISGID 0002000 /* set group id on execution */ #define S_ISVTX 0001000 /* save swapped text even after use */ #define S_IREAD 0000400 /* read permission, owner */ #define S_IWRITE 0000200 /* write permission, owner */ #define S_IEXEC 0000100 /* execute/search permission, owner */ The mode bits 0000070 and 0000007 encode group and others permissions (see chmod(2)).
When fd is associated with a pipe, fstat reports an ordinary file with an inode number, restricted permissions, and a length (that may not be correct).
NOTES
Applying fstat to a socket returns a zeroed buffer.
The fields in the stat structure currently marked st_spare1, st_spare2, and st_spare3 are intended to allow future expansion of inode time stamps to 64 bits. Their existence may cause problems for programs that depend on the time stamps being contiguous (in calls to utimes(2)).
RETURN VALUE
A successful call returns zero. A failed call returns -1 and sets errno as indicated below.
ERRORS
Stat and lstat will fail if one or more of the following are true:
[ENOTDIR] A component of the path prefix is not a directory.
[EPERM] The pathname contains a character with the high-order bit set.
[ENOENT] The pathname is too long.
[ENOENT] The named file does not exist.
[EACCES] Search permission is denied for a component of the path prefix.
[EFAULT] Buf or path points to an invalid address.
[ELOOP] The call encountered too many symbolic links in translating the pathname.
Fstat will fail if one or both of the following are true:
[EBADF] Fd is not a valid open file descriptor.
[EFAULT] Buf points to an invalid address.