sysconf_dump - Dump sysconf() values

sysconf_dump.c

#include <stdio.h>
#include <unistd.h>
#include <sys/sysctl.h>
#include <string.h>

#define SC_OPT(KEY) { .id = KEY, .label = #KEY }

typedef struct sc_opt {
	int id;
	char* label;
} sc_opt_t;

sc_opt_t vals[] = {
	SC_OPT(_SC_ARG_MAX), SC_OPT(_SC_CHILD_MAX), SC_OPT(_SC_CLK_TCK), SC_OPT(_SC_IOV_MAX), 
	SC_OPT(_SC_NGROUPS_MAX), SC_OPT(_SC_NPROCESSORS_CONF), SC_OPT(_SC_NPROCESSORS_ONLN),
	SC_OPT(_SC_OPEN_MAX), SC_OPT(_SC_PAGESIZE), SC_OPT(_SC_STREAM_MAX),
	SC_OPT(_SC_TZNAME_MAX), SC_OPT(_SC_JOB_CONTROL), SC_OPT(_SC_SAVED_IDS),
	SC_OPT(_SC_VERSION), SC_OPT(_SC_BC_BASE_MAX), SC_OPT(_SC_BC_DIM_MAX),
	SC_OPT(_SC_BC_SCALE_MAX), SC_OPT(_SC_BC_STRING_MAX), SC_OPT(_SC_COLL_WEIGHTS_MAX),
	SC_OPT(_SC_EXPR_NEST_MAX), SC_OPT(_SC_LINE_MAX), SC_OPT(_SC_RE_DUP_MAX), 
	SC_OPT(_SC_2_VERSION), SC_OPT(_SC_2_C_BIND), SC_OPT(_SC_2_C_DEV),
	SC_OPT(_SC_2_C_DEV), SC_OPT(_SC_2_CHAR_TERM), SC_OPT(_SC_2_FORT_DEV),
	SC_OPT(_SC_2_FORT_RUN), SC_OPT(_SC_2_LOCALEDEF), SC_OPT(_SC_2_SW_DEV),
	SC_OPT(_SC_2_UPE), SC_OPT(_SC_PHYS_PAGES)
};

const int SC_VALS_LEN = sizeof(vals) / sizeof(sc_opt_t);

int help(char *bin_name)
{
	printf("%s - print configurable system variables\n", bin_name);
	printf("Usage: sysconf [name|all]\n\n");
	printf("See sysconf manpage for more info\n\n");
	return 0;
}

void print_sc_val(sc_opt_t *val)
{
	int sc_value = sysconf(val->id);
	printf("%02x %-22s %d\n", val->id, val->label, sc_value);
}

int dump_all()
{
	for (int i=0; i<SC_VALS_LEN; i++) 
		print_sc_val(vals+i);	
	return 0;
}

sc_opt_t *sc_opt_from_str(char *str)
{
	for(int i=0; i<SC_VALS_LEN; i++)
		if (!strcmp(vals[i].label, str))
				return vals+i;
	return 0;	
}

char *arg2bin_name(int argc, char **argv)
{
	if (!argc) return "sysconf";
	return argv[0];
}

int main(int argc, char **argv)
{
	char* bin_name = arg2bin_name(argc, argv);
	if (argc < 2) return help(bin_name);

	char *name = argv[1];
	if (!strcmp(name, "all"))
		return dump_all();
	
	sc_opt_t *val = sc_opt_from_str(name);
	if (!val) {
		printf("Invalid argument: %s, see \"man sysconf\"\n", name);
		return -1;
	}

	print_sc_val(val);
	return 0;
}