verbosely printf

verbose_c.c

/* verbose_c : verbosely printf for old-c */
#include <stdio.h>
#include <stdarg.h>
extern int verbose_lvl;
extern verbose(int lvl,const char*fmt,...);

int verbose_lvl=3;
int verbose(int lvl,const char*fmt,...){
  int ret=0;
  va_list ap; 
  va_start(ap,fmt);
  if(verbose_lvl>=lvl) ret=vprintf(fmt,ap);
  va_end(ap);
  return ret;
}

int main(int argc,char* argv[]){
  verbose_lvl=3;
  verbose( 3,"This line is output. lvl=%d\n", verbose_lvl);
  verbose( 5,"This line is not output.\n");
  return 0;
}
/* output:
gcc verbose_c.c && ./.aout
This line is output. lvl=3
*/

verbose_m.c

/* verbose_m.c : verbosely printf for c99 */
#include <stdio.h>
extern int verbose_lvl;
#define verbose(err,...) do{if(verbose_lvl>=(err)){printf(__VA_ARGS__);}}while(0);

int verbose_lvl;
int main(int argc, char* argv[]) {
  verbose_lvl = 3;
  verbose( 3,"This line is output. lvl=%d\n", verbose_lvl);
  verbose( 5,"This line is not output.\n");
  return 0;
}
/* output:
gcc verbose_m.c && ./.aout
This line is output. lvl=3
*/