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       comedi_errno - number of last Comedilib error


       #include <comedilib.h>

       int comedi_errno (void );


       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().

       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.

       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().

       Note  that  comedi_errno()  is deliberately different than the variable
       errno.  This is to overcome difficulties in making errno thread-safe.

                                28 October 2007