DtMsgLogSetHandler(library call) DtMsgLogSetHandler(library call)
NAMEDtMsgLogSetHandler — installs an alternate message logging handler
SYNOPSIS
#include <Dt/MsgLog.h>
DtMsgLogHandler DtMsgLogSetHandler(
DtMsgLogHandler handler);
DESCRIPTION
The DtMsgLogSetHandler function installs an alternate message logging
handler that will be invoked when DtMsgLogMessage is called. If han‐
dler is NULL, the default handler is installed.
DtMsgLogSetHandler is optional and should be used only to override the
default message logging handler. If the handler function wants to log
a message, it must use the format and file specified in DtMsgLogMes‐
sage(3) so applications can reliably parse the log file. (If the han‐
dler wants to log a message, it can obtain the byte count to output by
using the return value from a call to vfprint.)
The DtMsgLogHandler handler function has the following arguments:
program_name
A string "tag" to identify the application issuing the mes‐
sage. This is generally an application's argv[0].
msg_type The message type.
format Specifies the sprintf format of the message.
args Specifies the variable number of arguments needed by format.
The handler function should not call DtMsgLogMessage.
A sample use of the DtMsgLogSetHandler function is in an application
that prints the CDE data types and actions databases. If an error
occurs when the databases are loaded, the error messages are logged and
the application is not able to get the messages. However, if the appli‐
cation installs a message logging handler, when the database loading
code encounters an error, the application's installed handler will be
invoked to give the application access to the database loading error
messages.
ARGUMENTS
handler Specifies a message handler function.
ENVIRONMENT VARIABLES
None.
RESOURCES
None.
ACTIONS/MESSAGES
None.
ERRORS/WARNINGS
None.
EXAMPLES
The following code installs a DtMsgLogHandler handler and then calls
DtDbLoad to load the CDE data typing and action databases. If an error
occurs when the databases are loaded, the handler function will be
invoked. The handler writes the message to an alternate file. After
the databases are loaded, the default handler is restored.
(void) DtMsgLogSetHandler (msglog_handler);
DtDbLoad ();
(void) DtMsgLogSetHandler (NULL);
void my_handler (
const char * prog_name,
DtMsgLogType msg_type,
const char * format,
va_list args)
{
FILE *fp;
fp = fopen ("/tmp/foo", "a+");
(void) fprintf (fp, "progname = %sformat = %smsg_type = %d0,
prog_name, format, msg_type);
(void) vfprintf (fp, format, args);
(void) fprintf (fp, "0);
}
RETURN VALUE
If DtMsgLogMessage completes successfully, it returns the previously
installed handler. If it fails, it returns NULL.
FILES
None.
SEE ALSODtMsgLogMessage(3), DtMsgLogOpenFile(3)
DtMsgLogSetHandler(library call)
