$ COPRTHR_CLMESG_LEVEL=3 ./executable
levels defined in coprthr/include/printcl.h:
#define CL_EMERG "<0>" /* system is unusable */
#define CL_ALERT "<1>" /* action must be taken immediately */
#define CL_CRIT "<2>" /* critical conditions */
#define CL_ERR "<3>" /* error conditions */
#define CL_WARNING "<4>" /* warning conditions */
#define CL_NOTICE "<5"> /* normal but significant condition */
#define CL_INFO "<6>" /* informational */
#define CL_DEBUG "<7>" /* debug-level messages */
or build copthr with appropiate options:
$ ./configure --enable-silent
or
$ ./configure --with-default-clmesg-level=LEVEL