prctl.2: ffix

[thirdparty/man-pages.git] / man2 / symlink.2

.\" This manpage is Copyright (C) 1992 Drew Eckhardt;
.\"             and Copyright (C) 1993 Michael Haardt, Ian Jackson.
.\"		and Copyright (C) 2006, 2014 Michael Kerrisk
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.\" Modified 1993-07-24 by Rik Faith
.\" Modified 1996-04-26 by Nick Duffek <nsd@bbc.com>
.\" Modified 1996-11-06 by Eric S. Raymond <esr@thyrsus.com>
.\" Modified 1997-01-31 by Eric S. Raymond <esr@thyrsus.com>
.\" Modified 2004-06-23 by Michael Kerrisk <mtk.manpages@gmail.com>
.\"
.TH SYMLINK 2 2017-09-15 "Linux" "Linux Programmer's Manual"
.SH NAME
symlink, symlinkat \- make a new name for a file
.SH SYNOPSIS
.nf
.B #include <unistd.h>
.PP
.BI "int symlink(const char *" target ", const char *" linkpath );

.BR "#include <fcntl.h>           " "/* Definition of AT_* constants */"
.B #include <unistd.h>
.PP
.BI "int symlinkat(const char *" target ", int " newdirfd \
", const char *" linkpath );
.PP
.fi
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.PP
.ad l
.BR symlink ():
.RS 4
_XOPEN_SOURCE\ >=\ 500 || _POSIX_C_SOURCE\ >=\ 200112L
.\"    || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
    || /* Glibc versions <= 2.19: */ _BSD_SOURCE
.RE
.PP
.BR symlinkat ():
.PD 0
.ad l
.RS 4
.TP 4
Since glibc 2.10:
_POSIX_C_SOURCE\ >=\ 200809L
.TP
Before glibc 2.10:
_ATFILE_SOURCE
.RE
.ad b
.PD
.SH DESCRIPTION
.BR symlink ()
creates a symbolic link named
.I linkpath
which contains the string
.IR target .
.PP
Symbolic links are interpreted at run time as if the contents of the
link had been substituted into the path being followed to find a file or
directory.
.PP
Symbolic links may contain
.I ..
path components, which (if used at the start of the link) refer to the
parent directories of that in which the link resides.
.PP
A symbolic link (also known as a soft link) may point to an existing
file or to a nonexistent one; the latter case is known as a dangling
link.
.PP
The permissions of a symbolic link are irrelevant; the ownership is
ignored when following the link, but is checked when removal or
renaming of the link is requested and the link is in a directory with
the sticky bit
.RB ( S_ISVTX )
set.
.PP
If
.I linkpath
exists, it will
.I not
be overwritten.
.SS symlinkat()
The
.BR symlinkat ()
system call operates in exactly the same way as
.BR symlink (),
except for the differences described here.
.PP
If the pathname given in
.I linkpath
is relative, then it is interpreted relative to the directory
referred to by the file descriptor
.I newdirfd
(rather than relative to the current working directory of
the calling process, as is done by
.BR symlink ()
for a relative pathname).
.PP
If
.I linkpath
is relative and
.I newdirfd
is the special value
.BR AT_FDCWD ,
then
.I linkpath
is interpreted relative to the current working
directory of the calling process (like
.BR symlink ()).
.PP
If
.I linkpath
is absolute, then
.I newdirfd
is ignored.
.SH RETURN VALUE
On success, zero is returned.
On error, \-1 is returned, and
.I errno
is set appropriately.
.SH ERRORS
.TP
.B EACCES
Write access to the directory containing
.I linkpath
is denied, or one of the directories in the path prefix of
.I linkpath
did not allow search permission.
(See also
.BR path_resolution (7).)
.TP
.B EDQUOT
The user's quota of resources on the filesystem has been exhausted.
The resources could be inodes or disk blocks, depending on the filesystem
implementation.
.TP
.B EEXIST
.I linkpath
already exists.
.TP
.B EFAULT
.IR target " or " linkpath " points outside your accessible address space."
.TP
.B EIO
An I/O error occurred.
.TP
.B ELOOP
Too many symbolic links were encountered in resolving
.IR linkpath .
.TP
.B ENAMETOOLONG
.IR target " or " linkpath " was too long."
.TP
.B ENOENT
A directory component in
.I linkpath
does not exist or is a dangling symbolic link, or
.I target
or
.I linkpath
is an empty string.
.TP
.B ENOMEM
Insufficient kernel memory was available.
.TP
.B ENOSPC
The device containing the file has no room for the new directory
entry.
.TP
.B ENOTDIR
A component used as a directory in
.I linkpath
is not, in fact, a directory.
.TP
.B EPERM
The filesystem containing
.I linkpath
does not support the creation of symbolic links.
.TP
.B EROFS
.I linkpath
is on a read-only filesystem.
.PP
The following additional errors can occur for
.BR symlinkat ():
.TP
.B EBADF
.I newdirfd
is not a valid file descriptor.
.TP
.B ENOENT
.I linkpath
is a relative pathname and
.IR newdirfd
refers to a directory that has been deleted.
.TP
.B ENOTDIR
.I linkpath
is relative and
.I newdirfd
is a file descriptor referring to a file other than a directory.
.SH VERSIONS
.BR symlinkat ()
was added to Linux in kernel 2.6.16;
library support was added to glibc in version 2.4.
.SH CONFORMING TO
.BR symlink ():
SVr4, 4.3BSD, POSIX.1-2001, POSIX.1-2008.
.\" SVr4 documents additional error codes EDQUOT and ENOSYS.
.\" See
.\" .BR open (2)
.\" re multiple files with the same name, and NFS.
.PP
.BR symlinkat ():
POSIX.1-2008.
.SH NOTES
No checking of
.I target
is done.
.PP
Deleting the name referred to by a symbolic link will actually delete the
file (unless it also has other hard links).
If this behavior is not desired, use
.BR link (2).
.SS Glibc notes
On older kernels where
.BR symlinkat ()
is unavailable, the glibc wrapper function falls back to the use of
.BR symlink ().
When
.I linkpath
is a relative pathname,
glibc constructs a pathname based on the symbolic link in
.IR /proc/self/fd
that corresponds to the
.IR newdirfd
argument.
.SH SEE ALSO
.BR ln (1),
.BR namei (1),
.BR lchown (2),
.BR link (2),
.BR lstat (2),
.BR open (2),
.BR readlink (2),
.BR rename (2),
.BR unlink (2),
.BR path_resolution (7),
.BR symlink (7)