411 lines
8.1 KiB
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411 lines
8.1 KiB
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML><HEAD><TITLE>Man page of SYMLINK</TITLE>
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</HEAD><BODY>
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<H1>SYMLINK</H1>
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Section: Linux Programmer's Manual (2)<BR>Updated: 2017-09-15<BR><A HREF="#index">Index</A>
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<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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symlink, symlinkat - make a new name for a file
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<PRE>
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<B>#include <<A HREF="file:///usr/include/unistd.h">unistd.h</A>></B>
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<B>int symlink(const char *</B><I>target</I><B>, const char *</B><I>linkpath</I><B>);</B>
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<B>#include <<A HREF="file:///usr/include/fcntl.h">fcntl.h</A>> </B>/* Definition of AT_* constants */
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<B>#include <<A HREF="file:///usr/include/unistd.h">unistd.h</A>></B>
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<B>int symlinkat(const char *</B><I>target</I><B>, int </B><I>newdirfd</I><B>, const char *</B><I>linkpath</I><B>);</B>
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</PRE>
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Feature Test Macro Requirements for glibc (see
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<B><A HREF="/cgi-bin/man/man2html?7+feature_test_macros">feature_test_macros</A></B>(7)):
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<P>
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<B>symlink</B>():
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<DL COMPACT><DT id="1"><DD>
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_XOPEN_SOURCE >= 500 || _POSIX_C_SOURCE >= 200112L
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<BR> || /* Glibc versions <= 2.19: */ _BSD_SOURCE
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</DL>
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<P>
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<B>symlinkat</B>():
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<DL COMPACT><DT id="2"><DD>
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<DL COMPACT>
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<DT id="3">Since glibc 2.10:<DD>
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_POSIX_C_SOURCE >= 200809L
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<DT id="4">Before glibc 2.10:<DD>
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_ATFILE_SOURCE
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</DL>
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</DL>
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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<B>symlink</B>()
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creates a symbolic link named
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<I>linkpath</I>
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which contains the string
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<I>target</I>.
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<P>
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Symbolic links are interpreted at run time as if the contents of the
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link had been substituted into the path being followed to find a file or
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directory.
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<P>
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Symbolic links may contain
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<I>..</I>
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path components, which (if used at the start of the link) refer to the
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parent directories of that in which the link resides.
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<P>
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A symbolic link (also known as a soft link) may point to an existing
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file or to a nonexistent one; the latter case is known as a dangling
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link.
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<P>
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The permissions of a symbolic link are irrelevant; the ownership is
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ignored when following the link, but is checked when removal or
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renaming of the link is requested and the link is in a directory with
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the sticky bit
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(<B>S_ISVTX</B>)
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set.
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<P>
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If
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<I>linkpath</I>
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exists, it will
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<I>not</I>
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be overwritten.
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<A NAME="lbAE"> </A>
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<H3>symlinkat()</H3>
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The
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<B>symlinkat</B>()
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system call operates in exactly the same way as
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<B>symlink</B>(),
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except for the differences described here.
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<P>
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If the pathname given in
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<I>linkpath</I>
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is relative, then it is interpreted relative to the directory
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referred to by the file descriptor
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<I>newdirfd</I>
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(rather than relative to the current working directory of
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the calling process, as is done by
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<B>symlink</B>()
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for a relative pathname).
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<P>
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If
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<I>linkpath</I>
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is relative and
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<I>newdirfd</I>
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is the special value
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<B>AT_FDCWD</B>,
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then
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<I>linkpath</I>
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is interpreted relative to the current working
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directory of the calling process (like
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<B>symlink</B>()).
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<P>
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If
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<I>linkpath</I>
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is absolute, then
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<I>newdirfd</I>
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is ignored.
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<A NAME="lbAF"> </A>
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<H2>RETURN VALUE</H2>
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On success, zero is returned.
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On error, -1 is returned, and
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<I>errno</I>
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is set appropriately.
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<A NAME="lbAG"> </A>
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<H2>ERRORS</H2>
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<DL COMPACT>
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<DT id="5"><B>EACCES</B>
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<DD>
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Write access to the directory containing
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<I>linkpath</I>
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is denied, or one of the directories in the path prefix of
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<I>linkpath</I>
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did not allow search permission.
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(See also
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<B><A HREF="/cgi-bin/man/man2html?7+path_resolution">path_resolution</A></B>(7).)
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<DT id="6"><B>EDQUOT</B>
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<DD>
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The user's quota of resources on the filesystem has been exhausted.
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The resources could be inodes or disk blocks, depending on the filesystem
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implementation.
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<DT id="7"><B>EEXIST</B>
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<DD>
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<I>linkpath</I>
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already exists.
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<DT id="8"><B>EFAULT</B>
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<DD>
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<I>target</I> or <I>linkpath</I> points outside your accessible address space.
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<DT id="9"><B>EIO</B>
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<DD>
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An I/O error occurred.
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<DT id="10"><B>ELOOP</B>
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<DD>
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Too many symbolic links were encountered in resolving
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<I>linkpath</I>.
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<DT id="11"><B>ENAMETOOLONG</B>
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<DD>
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<I>target</I> or <I>linkpath</I> was too long.
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<DT id="12"><B>ENOENT</B>
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<DD>
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A directory component in
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<I>linkpath</I>
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does not exist or is a dangling symbolic link, or
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<I>target</I>
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or
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<I>linkpath</I>
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is an empty string.
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<DT id="13"><B>ENOMEM</B>
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<DD>
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Insufficient kernel memory was available.
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<DT id="14"><B>ENOSPC</B>
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<DD>
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The device containing the file has no room for the new directory
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entry.
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<DT id="15"><B>ENOTDIR</B>
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<DD>
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A component used as a directory in
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<I>linkpath</I>
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is not, in fact, a directory.
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<DT id="16"><B>EPERM</B>
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<DD>
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The filesystem containing
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<I>linkpath</I>
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does not support the creation of symbolic links.
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<DT id="17"><B>EROFS</B>
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<DD>
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<I>linkpath</I>
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is on a read-only filesystem.
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</DL>
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<P>
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The following additional errors can occur for
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<B>symlinkat</B>():
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<DL COMPACT>
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<DT id="18"><B>EBADF</B>
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<DD>
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<I>newdirfd</I>
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is not a valid file descriptor.
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<DT id="19"><B>ENOENT</B>
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<DD>
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<I>linkpath</I>
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is a relative pathname and
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<I>newdirfd</I>
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refers to a directory that has been deleted.
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<DT id="20"><B>ENOTDIR</B>
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<DD>
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<I>linkpath</I>
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is relative and
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<I>newdirfd</I>
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is a file descriptor referring to a file other than a directory.
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</DL>
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<A NAME="lbAH"> </A>
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<H2>VERSIONS</H2>
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<B>symlinkat</B>()
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was added to Linux in kernel 2.6.16;
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library support was added to glibc in version 2.4.
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<A NAME="lbAI"> </A>
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<H2>CONFORMING TO</H2>
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<B>symlink</B>():
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SVr4, 4.3BSD, POSIX.1-2001, POSIX.1-2008.
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<P>
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<B>symlinkat</B>():
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POSIX.1-2008.
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<A NAME="lbAJ"> </A>
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<H2>NOTES</H2>
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No checking of
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<I>target</I>
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is done.
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<P>
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Deleting the name referred to by a symbolic link will actually delete the
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file (unless it also has other hard links).
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If this behavior is not desired, use
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<B><A HREF="/cgi-bin/man/man2html?2+link">link</A></B>(2).
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<A NAME="lbAK"> </A>
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<H3>Glibc notes</H3>
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On older kernels where
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<B>symlinkat</B>()
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is unavailable, the glibc wrapper function falls back to the use of
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<B>symlink</B>().
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When
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<I>linkpath</I>
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is a relative pathname,
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glibc constructs a pathname based on the symbolic link in
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<I>/proc/self/fd</I>
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that corresponds to the
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<I>newdirfd</I>
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argument.
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<A NAME="lbAL"> </A>
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<H2>SEE ALSO</H2>
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<B><A HREF="/cgi-bin/man/man2html?1+ln">ln</A></B>(1),
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<B><A HREF="/cgi-bin/man/man2html?1+namei">namei</A></B>(1),
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<B><A HREF="/cgi-bin/man/man2html?2+lchown">lchown</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+link">link</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+lstat">lstat</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+open">open</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+readlink">readlink</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+rename">rename</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+unlink">unlink</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?7+path_resolution">path_resolution</A></B>(7),
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<B><A HREF="/cgi-bin/man/man2html?7+symlink">symlink</A></B>(7)
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<A NAME="lbAM"> </A>
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<H2>COLOPHON</H2>
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This page is part of release 5.05 of the Linux
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<I>man-pages</I>
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project.
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A description of the project,
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information about reporting bugs,
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and the latest version of this page,
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can be found at
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<A HREF="https://www.kernel.org/doc/man-pages/.">https://www.kernel.org/doc/man-pages/.</A>
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<P>
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<HR>
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<A NAME="index"> </A><H2>Index</H2>
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<DL>
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<DT id="21"><A HREF="#lbAB">NAME</A><DD>
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<DT id="22"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="23"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DL>
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<DT id="24"><A HREF="#lbAE">symlinkat()</A><DD>
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</DL>
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<DT id="25"><A HREF="#lbAF">RETURN VALUE</A><DD>
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<DT id="26"><A HREF="#lbAG">ERRORS</A><DD>
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<DT id="27"><A HREF="#lbAH">VERSIONS</A><DD>
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<DT id="28"><A HREF="#lbAI">CONFORMING TO</A><DD>
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<DT id="29"><A HREF="#lbAJ">NOTES</A><DD>
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<DL>
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<DT id="30"><A HREF="#lbAK">Glibc notes</A><DD>
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</DL>
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<DT id="31"><A HREF="#lbAL">SEE ALSO</A><DD>
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<DT id="32"><A HREF="#lbAM">COLOPHON</A><DD>
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</DL>
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<HR>
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This document was created by
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<A HREF="/cgi-bin/man/man2html">man2html</A>,
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using the manual pages.<BR>
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Time: 00:05:35 GMT, March 31, 2021
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</BODY>
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</HTML>
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