479 lines
9.5 KiB
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479 lines
9.5 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 UNLINK</TITLE>
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</HEAD><BODY>
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<H1>UNLINK</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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unlink, unlinkat - delete a name and possibly the file it refers to
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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 unlink(const char *</B><I>pathname</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 unlinkat(int </B><I>dirfd</I><B>, const char *</B><I>pathname</I><B>, int </B><I>flags</I><B>);</B>
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</PRE>
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<P>
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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>unlinkat</B>():
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<DL COMPACT><DT id="1"><DD>
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<DL COMPACT>
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<DT id="2">Since glibc 2.10:<DD>
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_POSIX_C_SOURCE >= 200809L
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<DT id="3">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>unlink</B>()
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deletes a name from the filesystem.
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If that name was the
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last link to a file and no processes have the file open, the file is
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deleted and the space it was using is made available for reuse.
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<P>
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If the name was the last link to a file but any processes still have
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the file open, the file will remain in existence until the last file
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descriptor referring to it is closed.
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<P>
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If the name referred to a symbolic link, the link is removed.
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<P>
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If the name referred to a socket, FIFO, or device, the name for it is
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removed but processes which have the object open may continue to use
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it.
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<A NAME="lbAE"> </A>
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<H3>unlinkat()</H3>
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The
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<B>unlinkat</B>()
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system call operates in exactly the same way as either
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<B>unlink</B>()
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or
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<B><A HREF="/cgi-bin/man/man2html?2+rmdir">rmdir</A></B>(2)
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(depending on whether or not
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<I>flags</I>
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includes the
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<B>AT_REMOVEDIR</B>
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flag)
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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>pathname</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>dirfd</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>unlink</B>()
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and
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<B><A HREF="/cgi-bin/man/man2html?2+rmdir">rmdir</A></B>(2)
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for a relative pathname).
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<P>
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If the pathname given in
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<I>pathname</I>
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is relative and
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<I>dirfd</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>pathname</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>unlink</B>()
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and
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<B><A HREF="/cgi-bin/man/man2html?2+rmdir">rmdir</A></B>(2)).
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<P>
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If the pathname given in
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<I>pathname</I>
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is absolute, then
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<I>dirfd</I>
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is ignored.
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<P>
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<I>flags</I>
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is a bit mask that can either be specified as 0, or by ORing
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together flag values that control the operation of
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<B>unlinkat</B>().
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Currently, only one such flag is defined:
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<DL COMPACT>
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<DT id="4"><B>AT_REMOVEDIR</B>
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<DD>
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By default,
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<B>unlinkat</B>()
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performs the equivalent of
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<B>unlink</B>()
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on
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<I>pathname</I>.
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If the
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<B>AT_REMOVEDIR</B>
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flag is specified, then
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performs the equivalent of
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<B><A HREF="/cgi-bin/man/man2html?2+rmdir">rmdir</A></B>(2)
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on
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<I>pathname</I>.
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</DL>
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<P>
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See
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<B><A HREF="/cgi-bin/man/man2html?2+openat">openat</A></B>(2)
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for an explanation of the need for
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<B>unlinkat</B>().
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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>pathname</I>
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is not allowed for the process's effective UID, or one of the
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directories in
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<I>pathname</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>EBUSY</B>
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<DD>
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The file
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<I>pathname</I>
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cannot be unlinked because it is being used by the system
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or another process;
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for example, it is a mount point
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or the NFS client software created it to represent an
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active but otherwise nameless inode ("NFS silly renamed").
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<DT id="7"><B>EFAULT</B>
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<DD>
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<I>pathname</I>
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points outside your accessible address space.
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<DT id="8"><B>EIO</B>
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<DD>
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An I/O error occurred.
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<DT id="9"><B>EISDIR</B>
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<DD>
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<I>pathname</I>
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refers to a directory.
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(This is the non-POSIX value returned by Linux since 2.1.132.)
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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 translating
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<I>pathname</I>.
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<DT id="11"><B>ENAMETOOLONG</B>
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<DD>
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<I>pathname</I> was too long.
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<DT id="12"><B>ENOENT</B>
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<DD>
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A component in
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<I>pathname</I>
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does not exist or is a dangling symbolic link, or
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<I>pathname</I>
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is empty.
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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>ENOTDIR</B>
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<DD>
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A component used as a directory in
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<I>pathname</I>
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is not, in fact, a directory.
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<DT id="15"><B>EPERM</B>
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<DD>
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The system does not allow unlinking of directories,
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or unlinking of directories requires privileges that the
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calling process doesn't have.
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(This is the POSIX prescribed error return;
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as noted above, Linux returns
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<B>EISDIR</B>
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for this case.)
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<DT id="16"><B>EPERM</B> (Linux only)
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<DD>
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The filesystem does not allow unlinking of files.
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<DT id="17"><B>EPERM</B> or <B>EACCES</B>
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<DD>
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The directory containing
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<I>pathname</I>
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has the sticky bit
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(<B>S_ISVTX</B>)
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set and the process's effective UID is neither the UID of the file to
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be deleted nor that of the directory containing it, and
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the process is not privileged (Linux: does not have the
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<B>CAP_FOWNER</B>
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capability).
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<DT id="18"><B>EPERM</B>
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<DD>
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The file to be unlinked is marked immutable or append-only.
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(See
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<B><A HREF="/cgi-bin/man/man2html?2+ioctl_iflags">ioctl_iflags</A></B>(2).)
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<DT id="19"><B>EROFS</B>
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<DD>
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<I>pathname</I>
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refers to a file on a read-only filesystem.
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</DL>
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<P>
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The same errors that occur for
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<B>unlink</B>()
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and
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<B><A HREF="/cgi-bin/man/man2html?2+rmdir">rmdir</A></B>(2)
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can also occur for
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<B>unlinkat</B>().
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The following additional errors can occur for
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<B>unlinkat</B>():
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<DL COMPACT>
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<DT id="20"><B>EBADF</B>
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<DD>
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<I>dirfd</I>
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is not a valid file descriptor.
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<DT id="21"><B>EINVAL</B>
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<DD>
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An invalid flag value was specified in
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<I>flags</I>.
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<DT id="22"><B>EISDIR</B>
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<DD>
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<I>pathname</I>
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refers to a directory, and
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<B>AT_REMOVEDIR</B>
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was not specified in
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<I>flags</I>.
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<DT id="23"><B>ENOTDIR</B>
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<DD>
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<I>pathname</I>
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is relative and
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<I>dirfd</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>unlinkat</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>unlink</B>():
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SVr4, 4.3BSD, POSIX.1-2001, POSIX.1-2008.
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<P>
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<B>unlinkat</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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<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>unlinkat</B>()
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is unavailable, the glibc wrapper function falls back to the use of
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<B>unlink</B>()
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or
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<B><A HREF="/cgi-bin/man/man2html?2+rmdir">rmdir</A></B>(2).
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When
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<I>pathname</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>dirfd</I>
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argument.
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<A NAME="lbAL"> </A>
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<H2>BUGS</H2>
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Infelicities in the protocol underlying NFS can cause the unexpected
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disappearance of files which are still being used.
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<A NAME="lbAM"> </A>
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<H2>SEE ALSO</H2>
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<B><A HREF="/cgi-bin/man/man2html?1+rm">rm</A></B>(1),
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<B><A HREF="/cgi-bin/man/man2html?1+unlink">unlink</A></B>(1),
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<B><A HREF="/cgi-bin/man/man2html?2+chmod">chmod</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+mknod">mknod</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+rename">rename</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+rmdir">rmdir</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?3+mkfifo">mkfifo</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+remove">remove</A></B>(3),
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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="lbAN"> </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="24"><A HREF="#lbAB">NAME</A><DD>
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<DT id="25"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="26"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DL>
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<DT id="27"><A HREF="#lbAE">unlinkat()</A><DD>
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</DL>
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<DT id="28"><A HREF="#lbAF">RETURN VALUE</A><DD>
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<DT id="29"><A HREF="#lbAG">ERRORS</A><DD>
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<DT id="30"><A HREF="#lbAH">VERSIONS</A><DD>
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<DT id="31"><A HREF="#lbAI">CONFORMING TO</A><DD>
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<DT id="32"><A HREF="#lbAJ">NOTES</A><DD>
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<DL>
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<DT id="33"><A HREF="#lbAK">Glibc notes</A><DD>
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</DL>
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<DT id="34"><A HREF="#lbAL">BUGS</A><DD>
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<DT id="35"><A HREF="#lbAM">SEE ALSO</A><DD>
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<DT id="36"><A HREF="#lbAN">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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