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<!DOCTYPE concept
  PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
<concept id="GUID-00FFF2B3-F8E4-5CBF-B031-240D98BB2111" xml:lang="en"><title>External
Programs</title><prolog><metadata><keywords/></metadata></prolog><conbody>
<p>External programs are executables built outside but which can be launched
from the Zsh command prompt. </p>
<p>If the command is neither built-in, nor specified with an absolute pathname,
the shell will look in the <filepath>\sys\bin</filepath> on each drive in
reverse alphabetical order (<filepath>y:</filepath>, <filepath>x:</filepath>,...
to <filepath>b:</filepath>, <filepath>a:</filepath> and later <filepath>z:</filepath>)
and execute the first external program found. </p>
<p>To execute the external program directly give the following command at
the command-prompt: </p>
<p><userinput>command &lt;ext_pgm&gt;</userinput> </p>
<p>where <codeph>ext_pgm</codeph> is the name of the external program. </p>
<p>For example: </p>
<p>The program below reads input from Zsh and writes data to Zsh which can
then be redirected back to the Telnet client. </p>
<codeblock id="GUID-2A92BFF9-D69D-5C18-B657-9D7D5738EA22" xml:space="preserve">#include &lt;stdio.h&gt;
#include &lt;string.h&gt;
#include &lt;unistd.h&gt;

int  main()
    {
    char userData[20]; char ch; int x=0;
    
    memset(userData,0,20);
    x=read(0,userData, 20);    
        
    while(strcmp(userData, "quit"))
        {
        write(1, userData, x);
        memset(userData,0,20);
        x=read(0,userData, 20);        
        }        
    return 0;                 
    }
</codeblock>
<section id="GUID-A2C89E91-C5A5-49D9-A3A5-E9FB54A01BE1"><title>Limitations</title> <p>P.I.P.S. applications and native Symbian
applications can be launched from the Telnet client. However, to view the
output of the program or interact with it, the standard input and output of
the program must be accessible to the Telnet server. This is only possible
with P.I.P.S. applications. With native applications you will only be able
to retrieve the termination status; you will not be able to view the output
or interact with the program. </p> <p>Permission will be denied for external
programs that does not have the required capabilities to access directories
that contain <filepath>/sys</filepath> and <filepath>/private</filepath> in
their directory path. </p> <p> <b>Note:</b> For more information about the
external commands supported by Zsh, see the <xref href="GUID-3F577531-9798-537F-8F8B-7CAB0257560C.dita">Zsh
Command Syntax</xref> section. </p> </section>
<section id="GUID-164C2D77-8150-41FB-ABAB-FA1C52A59E21"><title>See also</title> <p>For information on porting Standard C
applications to the Symbian platform see the <xref href="GUID-E2DE2C6F-E071-5E88-96F1-D71DDED84609.dita">P.I.P.S.
Guide</xref>. </p> </section>
</conbody></concept>