dlinfo.3: ATTRIBUTES: Note function that is thread-safe

[thirdparty/man-pages.git] / man3 / statvfs.3

.\" Copyright (C) 2003 Andries Brouwer (aeb@cwi.nl)
.\"
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.\" The pathconf note is from Walter Harms
.\" This is not a system call on Linux
.\"
.\" Modified 2004-06-23 by Michael Kerrisk <mtk.manpages@gmail.com>
.\"
.TH STATVFS 3 2015-02-21 "Linux" "Linux Programmer's Manual"
.SH NAME
statvfs, fstatvfs \- get filesystem statistics
.SH SYNOPSIS
.B #include <sys/statvfs.h>
.sp
.BI "int statvfs(const char *" path ", struct statvfs *" buf );
.br
.BI "int fstatvfs(int " fd ", struct statvfs *" buf );
.SH DESCRIPTION
The function
.BR statvfs ()
returns information about a mounted filesystem.
.I path
is the pathname of any file within the mounted filesystem.
.I buf
is a pointer to a
.I statvfs
structure defined approximately as follows:

.in +4n
.nf
struct statvfs {
    unsigned long  f_bsize;    /* Filesystem block size */
    unsigned long  f_frsize;   /* Fragment size */
    fsblkcnt_t     f_blocks;   /* Size of fs in f_frsize units */
    fsblkcnt_t     f_bfree;    /* Number of free blocks */
    fsblkcnt_t     f_bavail;   /* Number of free blocks for
                                  unprivileged users */
    fsfilcnt_t     f_files;    /* Number of inodes */
    fsfilcnt_t     f_ffree;    /* Number of free inodes */
    fsfilcnt_t     f_favail;   /* Number of free inodes for
                                  unprivileged users */
    unsigned long  f_fsid;     /* Filesystem ID */
    unsigned long  f_flag;     /* Mount flags */
    unsigned long  f_namemax;  /* Maximum filename length */
};
.fi
.in

Here the types
.I fsblkcnt_t
and
.I fsfilcnt_t
are defined in
.IR <sys/types.h> .
Both used to be
.IR "unsigned long" .

The field
.I f_flag
is a bit mask indicating various options that were employed
when mounting this filesystem.
It contains zero or more of the following flags:
.\" XXX Keep this list in sync with statfs(2)
.TP
.B ST_MANDLOCK
Mandatory locking is permitted on the filesystem (see
.BR fcntl (2)).
.TP
.B ST_NOATIME
Do not update access times; see
.BR mount (2).
.TP
.B ST_NODEV
Disallow access to device special files on this filesystem.
.TP
.B ST_NODIRATIME
Do not update directory access times; see
.BR mount (2).
.TP
.B ST_NOEXEC
Execution of programs is disallowed on this filesystem.
.TP
.B ST_NOSUID
The set-user-ID and set-group-ID bits are ignored by
.BR exec (3)
for executable files on this filesystem
.TP
.B ST_RDONLY
This filesystem is mounted read-only.
.TP
.B ST_RELATIME
Update atime relative to mtime/ctime; see
.BR mount (2).
.TP
.B ST_SYNCHRONOUS
Writes are synched to the filesystem immediately (see the description of
.B O_SYNC
in
.BR open (2)).
.LP
It is unspecified whether all members of the returned struct
have meaningful values on all filesystems.

.BR fstatvfs ()
returns the same information about an open file referenced by descriptor
.IR fd .
.SH RETURN VALUE
On success, zero is returned.
On error, \-1 is returned, and
.I errno
is set appropriately.
.SH ERRORS
.TP
.B EACCES
.RB ( statvfs ())
Search permission is denied for a component of the path prefix of
.IR path .
(See also
.BR path_resolution (7).)
.TP
.B EBADF
.RB ( fstatvfs ())
.I fd
is not a valid open file descriptor.
.TP
.B EFAULT
.I Buf
or
.I path
points to an invalid address.
.TP
.B EINTR
This call was interrupted by a signal.
.TP
.B EIO
An I/O error occurred while reading from the filesystem.
.TP
.B ELOOP
.RB ( statvfs ())
Too many symbolic links were encountered in translating
.IR path .
.TP
.B ENAMETOOLONG
.RB ( statvfs ())
.I path
is too long.
.TP
.B ENOENT
.RB ( statvfs ())
The file referred to by
.I path
does not exist.
.TP
.B ENOMEM
Insufficient kernel memory was available.
.TP
.B ENOSYS
The filesystem does not support this call.
.TP
.B ENOTDIR
.RB ( statvfs ())
A component of the path prefix of
.I path
is not a directory.
.TP
.B EOVERFLOW
Some values were too large to be represented in the returned struct.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lbw21 lb lb
l l l.
Interface	Attribute	Value
T{
.BR statvfs (),
.BR fstatvfs ()
T}	Thread safety	MT-Safe
.TE
.SH CONFORMING TO
POSIX.1-2001, POSIX.1-2008.

Only the
.B ST_NOSUID
and
.B ST_RDONLY
flags of the
.I f_flag
field are specified in POSIX.1.
To obtain definitions of the remaining flags, one must define
.BR _GNU_SOURCE .
.SH NOTES
The Linux kernel has system calls
.BR statfs (2)
and
.BR fstatfs (2)
to support this library call.

In glibc versions before 2.13,
.\" glibc commit 3cdaa6adb113a088fdfb87aa6d7747557eccc58d
.BR statvfs ()
populated the bits of the
.IR f_flag
field by scanning the mount options shown in
.IR /proc/mounts .
However, starting with Linux 2.6.36, the underlying
.BR statfs (2)
system call provides the necessary information via the
.IR f_flags
field, and since glibc version 2.13, the
.BR statvfs ()
function will use information from that field rather than scanning
.IR /proc/mounts .

The glibc implementations of
.sp
.nf
   pathconf(path, _PC_REC_XFER_ALIGN);
   pathconf(path, _PC_ALLOC_SIZE_MIN);
   pathconf(path, _PC_REC_MIN_XFER_SIZE);
.fi
.sp
respectively use the
.IR f_frsize ,
.IR f_frsize ,
and
.I f_bsize
fields returned by a call to
.BR statvfs ()
with the argument
.IR path .
.SH SEE ALSO
.BR statfs (2)