<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN""http://www.w3.org/TR/html4/loose.dtd"> <HTML ><HEAD ><TITLE >comedi_errno</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK REL="HOME" TITLE=" Comedi " HREF="index.html"><LINK REL="UP" TITLE=" Comedi Function Reference " HREF="x4629.html#FUNCTIONREFERENCE"><LINK REL="PREVIOUS" TITLE="comedi_strerror" HREF="r4930.html"><LINK REL="NEXT" TITLE="comedi_fileno" HREF="r4973.html"></HEAD ><BODY CLASS="REFENTRY" BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#840084" ALINK="#0000FF" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" >Comedi: The <SPAN CLASS="emphasis" ><I CLASS="EMPHASIS" >Control and Measurement Device Interface</I ></SPAN > handbook </TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="r4930.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="r4973.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><H1 ><A NAME="FUNC-REF-COMEDI-ERRNO" ></A >comedi_errno</H1 ><DIV CLASS="REFNAMEDIV" ><A NAME="AEN4955" ></A ><H2 >Name</H2 >comedi_errno -- number of last Comedilib error</DIV ><DIV CLASS="REFSYNOPSISDIV" ><A NAME="AEN4958" ></A ><H2 >Synopsis</H2 ><DIV CLASS="FUNCSYNOPSIS" ><P ></P ><A NAME="AEN4959" ></A ><PRE CLASS="FUNCSYNOPSISINFO" >#include <comedilib.h></PRE ><P ><CODE ><CODE CLASS="FUNCDEF" >int comedi_errno</CODE >(void );</CODE ></P ><P ></P ></DIV ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN4966" ></A ><H2 > Description </H2 ><P >When a Comedilib function fails, it usually returns -1 or NULL, depending on the return type. An internal library variable stores an error number, which can be retrieved with comedi_errno(). This error number can be converted to a human-readable form by the functions comedi_perror() and comedi_strerror().</P ><P >These functions are intended to mimic the behavior of the standard C library functions perror(), strerror(), and errno. In particular, Comedilib functions sometimes return an error that is generated inside the C library; the comedi error message in this case is the same as the C library.</P ><P >The function comedi_errno() returns an integer describing the most recent comedilib error. This integer may be used as the errnum parameter for comedi_strerror().</P ><P >Note that comedi_errno() is deliberately different than the variable errno. This is to overcome difficulties in making errno thread-safe.</P ><P > </P ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="r4930.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="r4973.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >comedi_strerror</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="x4629.html#FUNCTIONREFERENCE" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >comedi_fileno</TD ></TR ></TABLE ></DIV ></BODY ></HTML >