Error reporting
Function: comedi_errno -- number of last Comedilib error
Retval: int
Param: void
Description:
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 by calling
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.
Function: comedi_loglevel -- change Comedilib logging properties
Retval: int
Param: int loglevel
Description:
This function affects the output of debugging and error messages
from Comedilib. By increasing the log level loglevel, additional debugging
information will be printed. Error and debugging messages are
printed to the standard error output stream stderr.
The default loglevel can be set by using the environment variable
COMEDI_LOGLEVEL. The default log level is 1.
In order to conserve resources, some debugging information is
disabled by default when Comedilib is compiled.
The meaning of the log levels is as follows:
LoglevelBehavior0Comedilib prints nothing.1
(default) Comedilib prints error messages when
there is a self-consistency error (i.e., an internal bug.)
2
Comedilib prints an error message when an invalid
parameter is passed.
3
Comedilib prints an error message whenever an
error is generated in the Comedilib library or in the C library,
when called by Comedilib.
4Comedilib prints a lot of junk.
Returns:
This function returns the previous log level.
Function: comedi_perror -- print a Comedilib error message
Retval: void
Param: const char * s
Description:
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 or
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_perror prints an error message to
the standard error output stream stderr.
The error message consists of the argument string
s, a colon, a
space, a description of the error condition, and a new line.
Function: comedi_strerror -- return string describing Comedilib error code
Retval: const char *
Param: int errnum
Description:
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
or 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_strerror returns a pointer to a
character string
describing the Comedilib error errnum.
The returned string may be
modified by a subsequent call to a strerr or
perror function
(either the libc or Comedilib versions).
An unrecognized error number will
return a pointer to the string undefined error, or similar.