STAT(2V) — SYSTEM CALLS

NAME

stat, lstat, fstat − get file status

SYNOPSIS

#include <sys/types.h>
#include <sys/stat.h>

int stat(path, buf)
char ∗path;
struct stat ∗buf;

int lstat(path, buf)
char ∗path;
struct stat ∗buf;

int 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(2V) call.

buf is a pointer to a stat structure into which information is placed concerning the file. A stat structure includes the following members:

dev_tst_dev;/∗ device file resides on ∗/
ino_tst_ino;/∗ the file serial number ∗/
mode_tst_mode;/∗ file mode ∗/
nlink_tst_nlink;/∗ number of hard links to the file ∗/
uid_tst_uid;/∗ user ID of owner ∗/
gid_tst_gid;/∗ group ID of owner ∗/
dev_tst_rdev;/∗ the device identifier (special files only)∗/
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;/∗ preferred blocksize for file system I/O∗/
longst_blocks;/∗ actual number of blocks allocated ∗/

st_atime Time when file data was last accessed. This can also be set explicitly by utimes(2). st_atime is not updated for directories searched during pathname resolution.

st_mtime Time when file data was last modified. This can also be set explicitly by utimes(2). It is not set by changes of owner, group, link count, or mode.

st_ctime Time when file status was last changed. It is set both both by writing and changing the file status information, such as changes of owner, group, link count, or mode.

The following macros test whether a file is of the specified type. The value m is the value of st_mode. Each macro evaluates to a non-zero value if the test is true or to zero if the test is false.

S_ISDIR(m) Test for directory file.

S_ISCHR(m) Test for character special file.

S_ISBLK(m) Test for block special file.

S_ISREG(m) Test for regular file.

S_ISLNK(m) Test for a symbolic link.

S_ISSOCK(m) Test for a socket.

S_ISFIFO(m) Test for pipe or FIFO special file.

The status information word st_mode is bit-encoded using the following masks and bits:

S_IRWXU Read, write, search (if a directory), or execute (otherwise) permissions mask for the owner of the file.

S_IRUSR Read permission bit for the owner of the file.

S_IWUSR Write permission bit for the owner of the file.

S_IXUSR Search (if a directory) or execute (otherwise) permission bit for the owner of the file.

S_IRWXG Read, write, search (if directory), or execute (otherwise) permissions mask for the file group class.

S_IRGRP Read permission bit for the file group class.

S_IWGRP Write permission bit for the file group class.

S_IXGRP Search (if a directory) or execute (otherwise) permission bit for the file group class.

S_IRWXO Read, write, search (if a directory), or execute (otherwise) permissions mask for the file other class.

S_IROTH Read permission bit for the file other class.

S_IWOTH Write permission bit for the file other class.

S_IXOTH Search (if a directory) or execute (otherwise) permission bit for the file other class.

S_ISUID Set user ID on execution. The process’s effective user ID is set to that of the owner of the file when the file is run as a program (see execve(2V)). On a regular file, this bit should be cleared on any write.

S_ISGID Set group ID on execution. The process’s effective group ID is set to that of the file when the file is run as a program (see execve(2V)). On a regular file, this bit should be cleared on any write.

In addition, the following bits and masks are made available for backward compatibility:

#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_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 ∗/

For more information on st_mode bits see chmod(2V).

RETURN VALUES

stat(), lstat() and fstat() return:

0 on success.

−1 on failure and set errno to indicate the error.

ERRORS

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

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

ELOOP Too many symbolic links were encountered in translating path.

ENAMETOOLONG The length of the path argument exceeds {PATH_MAX}.n

A pathname component is longer than {NAME_MAX} while {_POSIX_NO_TRUNC} is in effect (see pathconf(2V)).

ENOENT The file referred to by path does not exist.

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

fstat() will fail if one or more 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.

SYSTEM V ERRORS

In addition to the above, the following may also occur:

ENOENT path points to an empty string.

WARNINGS

The st_atime and st_mtime fields of the stat() are not contiguous. Programs that depend on them being contiguous (in calls to utimes(2) or utime(3V)) will not work.

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