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<title>link()--Create Link to File</title>
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<h2>link()--Create Link to File</h2>
<div class="box" style="width: 70%;">
<br>
&nbsp;&nbsp;Syntax<br>
<pre>
#include &lt;unistd.h&gt;
int link(const char <em>*existing</em>, const char <em>*new</em>);
</pre>
&nbsp;&nbsp;Service Program Name: QP0LLIB1<br>
<!-- iddvc RMBR -->
<br>
&nbsp;&nbsp;Default Public Authority: *USE<br>
<!-- iddvc RMBR -->
<br>
&nbsp;&nbsp;Threadsafe: Conditional; see <a href="#USAGE_NOTES">Usage Notes</a>.<br>
<!-- iddvc RMBR -->
<br>
</div>
<p>The <strong>link()</strong> function provides an alternative path name for
the existing file, so that the file can be accessed by either the existing name
or the new name. <strong>link()</strong> creates a link with a path name <em>
new</em> to an existing file whose path name is <em>existing</em>. The link can
be stored in the same directory as the original file or in a different
directory.</p>
<p>The <strong>link()</strong> function creates a hard link, which guarantees
the existence of a file even after the original path name has been removed.</p>
<p>If <strong>link()</strong> successfully creates the link, it increments the
<em>link count</em> of the file. The link count indicates how many links there
are to the file. If <strong>link()</strong> fails for some reason, the link
count is not incremented.</p>
<p>If the <em>existing</em> argument names a symbolic link, <strong>
link()</strong> creates a link that refers to the file that results from
resolving the path name contained in the symbolic link. If <em>new</em> names a
symbolic link, <strong>link()</strong> fails and sets <em>errno</em> to
[EEXIST].</p>
<p>A successful link updates the change time of the file, and the change time
and modification time of the directory that contains <em>new</em> (parent
directory).</p>
<p>If the file is checked out by another user (a user profile other than the
user profile of the current job), <strong>link()</strong> fails with the
[EBUSY] error.</p>
<p>Links created by this function are not allowed to cross file systems. For
example, you cannot create a link to a file in the QOpenSys directory from the
"root" (/) directory.</p>
<p>Links are not allowed to directories. If <em>existing</em> names a
directory, <strong>link()</strong> fails and sets <em>errno</em> to
[EPERM].</p>
<p>A job must have access to a file to link to it.</p>
<br>
<h3>Parameters</h3>
<dl>
<dt><strong><em>existing</em></strong></dt>
<dd>(Input) A pointer to a null-terminated path name naming an existing file to
which a new link is to be created.
<p>This parameter is assumed to be represented in the CCSID (coded character
set identifier) currently in effect for the job. If the CCSID of the job is
65535, this parameter is assumed to be represented in the default CCSID of the
job.</p>
<p>See <a href="linku.htm">QlgLink()--Create Link to File</a> for a description
and an example of supplying the <em>existing</em> in any CCSID.</p>
<br>
</dd>
<dt><strong><em>new</em></strong></dt>
<dd>(Input) A pointer to a null-terminated path name that is the name of the
new link.<br>
<br>
<p>This parameter is assumed to be represented in the CCSID currently in effect
for the job. If the CCSID of the job is 65535, this parameter is assumed to be
represented in the default CCSID of the job. The new link name is assumed to be
represented in the language and country or region currently in effect for the
job.</p>
<p>See <a href="linku.htm">QlgLink()--Create Link to File</a> for a description
and an example of supplying the <em>new</em> in any CCSID.</p>
</dd>
</dl>
<br>
<h3>Authorities</h3>
<p><strong>Note:</strong> Adopted authority is not used.</p>
<p><strong><a name="TBLALINK">Authorization Required for
link()</a></strong></p>
<table border>
<tr>
<th align="left" valign="bottom">Object Referred to</th>
<th align="center" valign="bottom">Authority Required</th>
<th align="left" valign="bottom">errno</th>
</tr>
<tr>
<td align="left" valign="top" width="75%">Each directory in the <em>
existing</em> path name that precedes the object being linked to</td>
<td align="center" valign="top" width="15%">*X</td>
<td align="left" valign="top" width="10%">EACCES</td>
</tr>
<tr>
<td align="left" valign="top"><em>Existing</em> object</td>
<td align="center" valign="top">*OBJEXIST</td>
<td align="left" valign="top">EACCES</td>
</tr>
<tr>
<td align="left" valign="top">Each directory in the <em>new</em> path name that
precedes the object being linked to</td>
<td align="center" valign="top">*X</td>
<td align="left" valign="top">EACCES</td>
</tr>
<tr>
<td align="left" valign="top">Parent directory of the new link</td>
<td align="center" valign="top">*WX</td>
<td align="left" valign="top">EACCES</td>
</tr>
</table>
<br>
<h3>Return Value</h3>
<dl compact>
<dt><em>0</em></dt>
<dd><strong>link()</strong> was successful.</dd>
<dt><em>-1</em></dt>
<dd><strong>link()</strong> was not successful. The <em>errno</em> global
variable is set to indicate the error.</dd>
</dl>
<br>
<h3>Error Conditions</h3>
<p>If <strong>link()</strong> is not successful, <em>errno</em> usually
indicates one of the following errors. Under some conditions, <em>errno</em>
could indicate an error other than those listed here.</p>
<table cellpadding="5">
<!-- cols="25 75" -->
<tr>
<th align="left" valign="bottom">Error condition</th>
<th align="left" valign="bottom">Additional information</th>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#EACCES">EACCES</a>]</em></td>
<td align="left" valign="top">
<p>If you are accessing a remote file through the Network File System, update
operations to file permissions at the server are not reflected at the client
until updates to data that is stored locally by the Network File System take
place. (Several options on the Add Mounted File System (ADDMFS) command
determine the time between refresh operations of local data.) Access to a
remote file may also fail due to different mappings of user IDs (UID) or group
IDs (GID) on the local and remote systems.</p>
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#EAGAIN">EAGAIN</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#EBADFID">EBADFID</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#EBADNAME">EBADNAME</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#EBUSY">EBUSY</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#ECONVERT">ECONVERT</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#EDAMAGE">EDAMAGE</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#EEXIST">EEXIST</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#EFAULT">EFAULT</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#EFILECVT">EFILECVT</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#EINVAL">EINVAL</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#EIO">EIO</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#EISDIR">EISDIR</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#EJRNDAMAGE">EJRNDAMAGE</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#EJRNENTTOOLONG">EJRNENTTOOLONG</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#EJRNINACTIVE">EJRNINACTIVE</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#EJRNRCVSPC">EJRNRCVSPC</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#ELOOP">ELOOP</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#EMLINK">EMLINK</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#ENAMETOOLONG">ENAMETOOLONG</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#ENEWJRN">ENEWJRN</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#ENEWJRNRCV">ENEWJRNRCV</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#ENOENT">ENOENT</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#ENOMEM">ENOMEM</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#ENOSPC">ENOSPC</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#ENOSYS">ENOSYS</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#ENOTAVAIL">ENOTAVAIL</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#ENOTDIR">ENOTDIR</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#ENOTSAFE">ENOTSAFE</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#ENOTSUP">ENOTSUP</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#EPERM">EPERM</a>]</em></td>
<td align="left" valign="top">
<p>Links to directories are not supported.</p>
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#EROOBJ">EROOBJ</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#ESTALE">ESTALE</a>]</em></td>
<td align="left" valign="top">
<p>If you are accessing a remote file through the Network File System, the file
may have been deleted at the server.</p>
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#EUNKNOWN">EUNKNOWN</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
<tr>
<td align="left" valign="top">
<em>[<a href="unix14.htm#EXDEV">EXDEV</a>]</em></td>
<td align="left" valign="top">
&nbsp;
</td>
</tr>
</table>
<br>
<br>
<h3>Error Messages</h3>
<p>The following messages may be sent from this function:</p>
<table width="100%">
<tr>
<th align="left" valign="top">Message ID</th>
<th align="left" valign="top">Error Message Text</th>
</tr>
<tr>
<td width="15%" valign="top">CPE3418 E</td>
<td width="85%" valign="top">Possible APAR condition or hardware failure.</td>
</tr>
<tr>
<td valign="top">CPFA0D4 E</td>
<td valign="top">File system error occurred. Error number &amp;1.</td>
</tr>
<tr>
<td valign="top">CPF3CF2 E</td>
<td valign="top">Error(s) occurred during running of &amp;1 API.</td>
</tr>
<tr>
<td valign="top">CPF9872 E</td>
<td valign="top">Program or service program &amp;1 in library &amp;2 ended.
Reason code &amp;3.</td>
</tr>
</table>
<br>
<h3><a name="usage_notes">Usage Notes</a></h3>
<ol type="1">
<li>This function will fail with error code [ENOTSAFE] when all the following
conditions are true:<br>
<br>
<ul>
<li>Where multiple threads exist in the job.<br>
</li>
<li>The object on which this function is operating resides in a file system
that is not threadsafe. Only the following file systems are threadsafe for this
function:<br>
<br>
<ul>
<li>"Root" (/)</li>
<li>QOpenSys</li>
<li>User-defined</li>
<li>QNTC</li>
<li>QSYS.LIB</li>
<li>Independent ASP QSYS.LIB</li>
<li>QOPT</li>
<li>Network File System</li>
<li>QFileSvr.400</li>
</ul>
</li>
</ul>
<br>
</li>
<li>The <strong>link()</strong> function should be used sparingly to avoid
potential performance degradation. The greater the number of hard links to an
object, the more time it will take to change the attributes of the object.<br><br>
</li>
<li>The following file systems do not support <strong>link()</strong>:</p>
<ul>
<li>QSYS.LIB</li>
<li>Independent ASP QSYS.LIB</li>
<li>QDLS</li>
<li>QOPT</li>
<li>QFileSvr.400</li>
<li>QNetWare</li>
<li>QNTC</li>
</ul>
<p>If <strong>link()</strong> is used in any of these file systems, a [ENOSYS]
error is returned.</p>
</li>
</ol>
<br>
<h3>Related Information</h3>
<ul>
<li>The &lt;<strong>unistd.h</strong>&gt; file (see <a href="unix13.htm">Header
Files for UNIX-Type Functions</a>)<br>
</li>
<li><a href="linku.htm">QlgLink()</a>--Create Link to File<br>
</li>
<li><a href="renamefs.htm">rename()</a>--Rename File or Directory<br>
</li>
<li><a href="unlink.htm">unlink()</a>--Remove Link to File</li>
</ul>
<br>
<h3>Example</h3>
<p>See <a href="../apiref/aboutapis.htm#codedisclaimer">Code disclaimer information</a>
for information pertaining to code examples.</p>
<p>The following example uses <strong>link()</strong>:</p>
<pre>
#include &lt;stdio.h&gt;
#include &lt;unistd.h&gt;
#include &lt;sys/types.h&gt;
#include &lt;sys/stat.h&gt;
#include &lt;fcntl.h&gt;
#include &lt;stdlib.h&gt;
main()
{
char fn[]="link.example.file";
char ln[]="link.example.link";
int file_descriptor;
struct stat info;
if ((file_descriptor = creat(fn, S_IWUSR)) &lt; 0)
perror("creat() error");
else {
close(file_descriptor);
puts("before link()");
stat(fn,&amp;info);
printf(" number of links is %hu\n",info.st_nlink);
if (link(fn, ln) != 0) {
perror("link() error");
unlink(fn);
}
else {
puts("after link()");
stat(fn,&amp;info);
printf(" number of links is %hu\n",info.st_nlink);
unlink(ln);
puts("after first unlink()");
stat(fn,&amp;info);
printf(" number of links is %hu\n",info.st_nlink);
unlink(fn);
}
}
}
</pre>
<p><strong>Output:</strong></p>
<pre>
before link()
number of links is 1
after link()
number of links is 2
after first unlink()
number of links is 1
</pre>
<br>
<hr>
API introduced: V3R1
<hr>
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