character in the command. The simplest useful command is something

like

<programlisting>

archive_command = 'cp -i %p /mnt/server/archivedir/%f &lt;/dev/null'

archive_command = 'test ! -f /mnt/server/archivedir/%f && cp %p /mnt/server/archivedir/%f' # Unix

archive_command = 'copy "%p" "C:\\server\\archivedir\\%f"' # Windows

</programlisting>

which will copy archivable WAL segments to the directory

<filename>/mnt/server/archivedir</>. (This is an example, not a

preserve the integrity of your archive in case of administrator error

(such as sending the output of two different servers to the same archive

directory).

</para>

<para>

It is advisable to test your proposed archive command to ensure that it

indeed does not overwrite an existing file, <emphasis>and that it returns

nonzero status in this case</>. We have found that <literal>cp -i</> does

this correctly on some platforms but not others. If the chosen command

does not itself handle this case correctly, you should add a command

to test for pre-existence of the archive file. For example, something

like

<programlisting>

archive_command = 'test ! -f .../%f &amp;&amp; cp %p .../%f'

</programlisting>

works correctly on most Unix variants.

nonzero status in this case</>.

The example command above for Unix ensures this by including a separate

<command>test</> step. On some Unix platforms, <command>cp</> has

switches such as <option>-i</> that can be used to do the same thing

less verbosely, but you should not rely on these without verifying that

the right exit status is returned. (In particular, GNU <command>cp</>

will return status zero when <option>-i</> is used and the target file

already exists, which is <emphasis>not</> the desired behavior.)

</para>

<para>