STAT(2) — SYSTEM CALLS

NAME

stat, lstat, fstat − get file status

SYNOPSIS

#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 named by path. Read, write or execute permission of the named file is not required, but all directories listed in the path name leading to the file must be searchable.

lstat is like stat except in the case where the named file is a symbolic link, in which case lstat returns information about the link, while stat returns information about the file the link references.

fstat obtains the same information about an open file referenced by the argument descriptor, such as would be obtained by an open call.

buf is a pointer to a stat structure into which information is placed concerning the file. The contents of the structure pointed to by buf include the following members:

dev_tst_dev;/∗ device inode resides on ∗/
ino_tst_ino;/∗ this inode’s number ∗/
u_shortst_mode;/∗ protection ∗/
shortst_nlink;/∗ number of hard links to the file ∗/
shortst_uid;/∗ user ID of owner ∗/
shortst_gid;/∗ group ID of owner ∗/
dev_tst_rdev;/∗ the device type, for inode that is device ∗/
off_tst_size;/∗ total size of file, in bytes ∗/
time_tst_atime;/∗ file last access time ∗/
time_tst_mtime;/∗ file last modify time ∗/
time_tst_ctime;/∗ file last status change time ∗/
longst_blksize;/∗ optimal blocksize for file system i/o ops ∗/
longst_blocks;/∗ actual number of blocks allocated ∗/

st_atime Time when file data was last read or modified. Changed by the following system calls: mknod(2), utimes(2), read(2V), write(2V), and truncate(2). For reasons of efficiency, st_atime is not set when a directory is searched, although this would be more logical.

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(2V).

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), rename(2), unlink(2), utimes(2), write(2V), truncate(2).

The status information word st_mode has bits:

#define    S_IFMT0170000/∗ type of file ∗/
#define    S_IFIFO0010000/∗ fifo special ∗/
#define    S_IFCHR0020000/∗ character special ∗/
#define    S_IFDIR0040000/∗ directory ∗/
#define    S_IFBLK0060000/∗ block special ∗/
#define    S_IFREG0100000/∗ regular file ∗/
#define    S_IFLNK0120000/∗ symbolic link ∗/
#define    S_IFSOCK0140000 /∗ socket ∗/
#define    S_ISUID0004000/∗ set user id on execution ∗/
#define    S_ISGID0002000/∗ set group id on execution ∗/
#define    S_ISVTX0001000/∗ save swapped text even after use ∗/
#define    S_IREAD0000400/∗ read permission, owner ∗/
#define    S_IWRITE0000200 /∗ write permission, owner ∗/
#define    S_IEXEC0000100/∗ execute/search permission, owner ∗/

The mode bits 0000070 and 0000007 encode group and others permissions (see chmod(2)).

RETURN VALUE

Upon successful completion a value of 0 is returned. Otherwise, a value of −1 is returned and errno is set to indicate the error.

ERRORS

stat and lstat will fail if one or more of the following are true:

ENOTDIR A component of the path prefix of path is not a directory.

EINVAL path contains a character with the high-order bit set.

ENAMETOOLONG
The length of a component of path exceeds 255 characters, or the length of path exceeds 1023 characters.

ENOENT The file referred to by path does not exist.

EACCES Search permission is denied for a component of the path prefix of path.

ELOOP Too many symbolic links were encountered in translating path.

EFAULT buf or path points to an invalid address.

EIO An I/O error occurred while reading from or writing to the file system.

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.

EIO An I/O error occurred while reading from or writing to the file system.

CAVEAT

The fields in the stat structure currently marked st_spare1, st_spare2, and st_spare3 are present in preparation for inode time stamps expanding to 64 bits. This, however, can break certain programs which depend on the time stamps being contiguous (in calls to utimes(2)).

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