打印所有可能的sysconf和pathconf值

#include "apue.h"
#include <errno.h>
#include <limits.h>

static void pr_sysconf(char *,int);
static void pr_pathconf(char *,char *,int);

int main(int argc,char *argv[])
{
	if(argc!=2)
		err_quit("usage: ./printall <dirname>");
	
#ifdef ARG_MAX
	printf("ARG_MAX defined to be %d\n",ARG_MAX+0);
#else
	printf("no symbol for ARG_MAX\n");
#endif

#ifdef _SC_ARG_MAX
	pr_sysconf("ARG_MAX =",_SC_ARG_MAX);
#else
	printf("no symbol for _SC_ARG_MAX\n");
#endif

#ifdef MAX_CANON
	printf("MAX_CANON defined to be %d\n",MAX_CANON+0);
#else
	printf("no symbol for MAX_CANON\n");
#endif

#ifdef _PC_MAX_CANON
	pr_pathconf("MAX_CANON =",argv[1],_PC_MAX_CANON);
#else
	printf("no symbol for _PC_MAX_CANON\n");
#endif

	exit(0);
}

static void pr_sysconf(char *mesg,int name)
{
	long val;
	fputs(mesg,stdout);
	errno=0;
	if((val = sysconf(name)) <0){
		if(errno !=0){
			if(errno !=0)
				fputs(" (not supported)\n",stdout);
			else
				err_sys("sysconf error");		
		}else{
			fputs(" (no limit)\n",stdout);
		}
	}else{
		printf(" %ld\n",val);
   	}
}

static void pr_pathconf(char *mesg,char *path,int name)
{
	long val;
	fputs(mesg,stdout);
	errno=0;
	if((val = pathconf(path, name)) <0){
		if(errno !=0){
			if(errno == EINVAL)
				fputs(" (no supported)\n",stdout);
			else
				err_sys("pathocnf error, path = %s",path);
		}else{
			fputs(" (no limit)\n",stdout);	
		}
	}else{
		printf(" %ld\n",val);
	}
}