Howto: Configure the logger from a program¶

The following example shows how to configure the logger from a program (without the need for a log config file):

#include "dcmtk/config/osconfig.h" 
#include "dcmtk/oflog/oflog.h" 

int main(int argc, char *argv[])
{
    /* enable verbose mode (info log level) */
    OFLog::configure(OFLogger::INFO_LOG_LEVEL);

    /* ... */
}

Log Levels¶

The following log levels are available. Every log level in this list includes the details of the above level (e.g. the WARN_LOG_LEVEL also outputs all errors and thus also fatal errors).

• FATAL_LOG_LEVEL: Only fatal error messages are printed.
• ERROR_LOG_LEVEL: All errors are printed.
• WARN_LOG_LEVEL: Warnings are printed.
• INFO_LOG_LEVEL: The most important processing information is printed.
• DEBUG_LOG_LEVEL: This is a pretty verbose logging level that is a good starting point for getting more information what actually happens in the code and to identify corresponding problems.
• TRACE_LOG_LEVEL: This is the most verbose logging level and outputs many processing details.

Redirecting log output to a file¶

If the log output should be directed to a file or another log pattern should be used, we need some more lines of code:

#include "dcmtk/config/osconfig.h" 
#include "dcmtk/oflog/fileap.h" 

int main(int argc, char *argv[])
{
    /* specify log pattern */
    OFunique_ptr<log4cplus::Layout> layout(new log4cplus::PatternLayout("%D{%Y-%m-%d %H:%M:%S.%q} %5p: %m%n"));
    /* Denote that a log file should be used that is appended to. The file is re-created every
       time the code gets to this point.
     */
    log4cplus::SharedAppenderPtr logfile(new log4cplus::FileAppender("example.log"));
    logfile->setLayout(OFmove(layout));

    /* make sure that only the file logger is used */
    log4cplus::Logger log = log4cplus::Logger::getRoot();
    log.removeAllAppenders();
    log.addAppender(logfile);
    log.setLogLevel(OFLogger::INFO_LOG_LEVEL);

    /* ...*/
}

The above code re-creates the example.log file every time the code is encountered, i.e. if the complete program is restarted. If you want to append a file without deleting it, use the following line instead

  log4cplus::SharedAppenderPtr logfile(new log4cplus::FileAppender("example.log", STD_NAMESPACE ios::app));

No output at all (quiet mode)¶

If all log output should be discarded:

#include "dcmtk/config/osconfig.h" 
#include "dcmtk/oflog/nullap.h" 

int main(int argc, char *argv[])
{
    log4cplus::SharedAppenderPtr nullapp(new log4cplus::NullAppender());

    /* make sure that only the null logger is used */
    log4cplus::Logger log = log4cplus::Logger::getRoot();
    log.removeAllAppenders();
    log.addAppender(nullapp);

    /* ...*/
}

Note¶

Please note that the above sample code requires DCMTK 3.5.5 (20091222) or newer.

Please also note that the namespace has changed after the DCMTK 3.6.0 release from log4cplus to dcmtk::log4cplus with this commit.

Please also note that older versions of DCMTK (prior to commit 3a54504640c35a) required the use of the no longer available OFauto_ptr instead of OFunique_ptr.