NetBSD/lib/libc/sys/stat.2

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.\"     @(#)stat.2	8.4 (Berkeley) 5/1/95
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.Dd May 1, 1995
.Dt STAT 2
.Os
.Sh NAME
.Nm stat ,
.Nm lstat ,
.Nm fstat
.Nd get file status
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <sys/stat.h>
.Ft int
.Fn stat "const char *path" "struct stat *sb"
.Ft int
.Fn lstat "const char *path" "struct stat *sb"
.Ft int
.Fn fstat "int fd" "struct stat *sb"
.Sh DESCRIPTION
The
.Fn stat
function obtains information about the file pointed to by
.Fa 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.
.Pp
.Fn lstat
is like
.Fn stat
except in the case where the named file is a symbolic link,
in which case
.Fn lstat
returns information about the link,
while
.Fn stat
returns information about the file the link references.
.Pp
The
.Fn fstat
function obtains the same information about an open file
known by the file descriptor
.Fa fd .
.Pp
The
.Fa sb
argument is a pointer to a
.Fn stat
structure
as defined by
.Aq Pa sys/stat.h
(shown below)
and into which information is placed concerning the file.
.Bd -literal
struct stat {
    dev_t     st_dev;     /* inode's device */
    ino_t     st_ino;     /* inode's number */
    mode_t    st_mode;    /* inode protection mode */
    nlink_t   st_nlink;   /* number or hard links to the file */
    uid_t     st_uid;     /* user-id of owner */
    gid_t     st_gid;     /* group-id of owner */
    dev_t     st_rdev;    /* device type, for special file inode */
    struct timespec st_atimespec;  /* time of last access */
    struct timespec st_mtimespec;  /* time of last data modification */
    struct timespec st_ctimespec;  /* time of last file status change */
    off_t     st_size;    /* file size, in bytes */
    int64_t   st_blocks;  /* blocks allocated for file */
    u_int32_t st_blksize; /* optimal file sys I/O ops blocksize */
    u_int32_t st_flags;   /* user defined flags for file */
    u_int32_t st_gen;     /* file generation number */
};
.Ed
.Pp
The time-related fields of
.Fa struct stat
are as follows:
.Bl -tag -width XXXst_mtime
.It st_atime
Time when file data was last accessed.
Changed by the
.Xr mknod 2 ,
.Xr utimes 2
and
.Xr read 2
system calls.
.It st_mtime
Time when file data was last modified.
Changed by the
.Xr mknod 2 ,
.Xr utimes 2
and
.Xr write 2
system calls.
.It st_ctime
Time when file status was last changed (inode data modification).
Changed by the
.Xr chflags 2 ,
.Xr chmod 2 ,
.Xr chown 2 ,
.Xr link 2 ,
.Xr mknod 2 ,
.Xr rename 2 ,
.Xr unlink 2 ,
.Xr utimes 2
and
.Xr write 2
system calls.
.El
.Pp
The size-related fields of the
.Fa struct stat
are as follows:
.Bl -tag -width XXXst_blksize
.It st_blksize
The optimal I/O block size for the file.
.It st_blocks
The actual number of blocks allocated for the file in 512-byte units.
As short symbolic links are stored in the inode, this number may
be zero.
.El
.Pp
The status information word
.Fa st_mode
has the following bits:
.Bd -literal
#define S_IFMT 0170000           /* type of file */
#define        S_IFIFO  0010000  /* named pipe (fifo) */
#define        S_IFCHR  0020000  /* character special */
#define        S_IFDIR  0040000  /* directory */
#define        S_IFBLK  0060000  /* block special */
#define        S_IFREG  0100000  /* regular */
#define        S_IFLNK  0120000  /* symbolic link */
#define        S_IFSOCK 0140000  /* socket */
#define        S_IFWHT  0160000  /* whiteout */
#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_IRUSR 0000400  /* read permission, owner */
#define S_IWUSR 0000200  /* write permission, owner */
#define S_IXUSR 0000100  /* execute/search permission, owner */
#define S_IRGRP 0000040  /* read permission, group */
#define S_IWGRP 0000020  /* write permission, group */
#define S_IXGRP 0000010  /* execute/search permission, group */
#define S_IROTH 0000004  /* read permission, other */
#define S_IWOTH 0000002  /* write permission, other */
#define S_IXOTH 0000001  /* execute/search permission, other */
.Ed
.Pp
For a list of access modes, see
.Aq Pa sys/stat.h ,
.Xr access 2
and
.Xr chmod 2 .
.Pp
The status information word
.Fa st_flags
has the following bits:
.Bd -literal
#define UF_NODUMP	0x00000001 /* do not dump file */
#define UF_IMMUTABLE	0x00000002 /* file may not be changed */
#define UF_APPEND	0x00000004 /* writes to file may only append */
#define UF_OPAQUE	0x00000008 /* directory is opaque wrt. union */
#define SF_ARCHIVED	0x00010000 /* file is archived */
#define SF_IMMUTABLE	0x00020000 /* file may not be changed */
#define SF_APPEND	0x00040000 /* writes to file may only append */
.Ed
.Pp
For a description of the flags, see
.Xr chflags 2 .
.Sh RETURN VALUES
Upon successful completion a value of 0 is returned.
Otherwise, a value of -1 is returned and
.Va errno
is set to indicate the error.
.Sh COMPATIBILITY
Previous versions of the system used different types for the
.Li st_dev ,
.Li st_uid ,
.Li st_gid ,
.Li st_rdev ,
.Li st_size ,
.Li st_blksize
and
.Li st_blocks
fields.
.Sh ERRORS
.Fn stat
and
.Fn lstat
will fail if:
.Bl -tag -width Er
.It Bq Er ENOTDIR
A component of the path prefix is not a directory.
.It Bq Er ENAMETOOLONG
A component of a pathname exceeded 
.Dv {NAME_MAX}
characters, or an entire path name exceeded 
.Dv {PATH_MAX}
characters.
.It Bq Er ENOENT
The named file does not exist.
.It Bq Er EACCES
Search permission is denied for a component of the path prefix.
.It Bq Er ELOOP
Too many symbolic links were encountered in translating the pathname.
.It Bq Er EFAULT
.Fa sb
or
.Em name
points to an invalid address.
.It Bq Er EIO
An I/O error occurred while reading from or writing to the file system.
.El
.Pp
.Bl -tag -width Er
.Fn fstat
will fail if:
.It Bq Er EBADF
.Fa fd
is not a valid open file descriptor.
.It Bq Er EFAULT
.Fa sb
points to an invalid address.
.It Bq Er EIO
An I/O error occurred while reading from or writing to the file system.
.El
.Sh SEE ALSO
.Xr chflags 2 ,
.Xr chmod 2 ,
.Xr chown 2 ,
.Xr utimes 2 ,
.Xr symlink 7
.Sh BUGS
Applying
.Fn fstat
to a socket (and thus to a pipe)
returns a zero'd buffer,
except for the blocksize field,
and a unique device and inode number.
.Sh STANDARDS
The
.Fn stat
and
.Fn fstat
functions conform to 
.St -p1003.1-90 .
.Sh HISTORY
A
.Fn lstat
function call appeared in
.Bx 4.2 .