add README.md to explain the purposes of the project better.

README.md

@@ -0,0 +1,10 @@
+# cpusetcores
+This is a utility application for managing CPU cores / threads on Linux machines.
+It allows you to enable/disable threads (via reading/writing to `/sys/devices/system/cpu/cpuX/online`).
+
+The plan is to eventually through deamons or some kernel magic to manage the amount of cores automatically, in hopes of saving power.
+How well this'll work and how much power is gained from it is still researched and the project is not actively being worked on.
+So for now it just serves as something faster than a shell script.
+
+I assume the kernel likely already has things for this, or it is being worked on.
+I just haven't looked into it that much yet, since I haven't really started the project yet.

src/opts.c

@@ -1,44 +1,49 @@
 #include "opts.h"
 
+#include <errno.h>
 #include <getopt.h>
 #include <stdint.h>
 #include <stdlib.h>
 
 #include "error.h"
+#include "util/intdef.h"
 
-uint8_t getoptions(int32_t argc, char *const *argv, int32_t *ncpus) {
+u8 getoptions(int argc, char *const *argv, int *ncpus) {
+	*ncpus = -1;
 	uint8_t opts = 0;
 	char opt;
 
-	while ((opt = getopt(argc, argv, "lavi")) != -1) {
+	while ((opt = getopt(argc, argv, "lavih")) != -1) {
 		switch (opt) {
-		case 'l':
+		case 'l': opts |= OPT_LIST_CORES; break;
-			if (opts & OPT_LIST_CORES) fatal("-%c has already been set", 'l');
+		case 'a': opts |= OPT_SET_ALL; break;
-			opts |= OPT_LIST_CORES;
+		case 'v': opts |= OPT_VERBOSE | OPT_LIST_CORES; break;
-			break;
+		case 'i': opts |= OPT_INVERT; break;
-		case 'a':
-			if (opts & OPT_SET_ALL) fatal("-%c has already been set", 'a');
-			opts |= OPT_SET_ALL;
-			break;
-		case 'v':
-			if (opts & OPT_VERBOSE) fatal("-%c has already been set", 'v');
-			opts |= OPT_VERBOSE | OPT_LIST_CORES;
-			break;
-		case 'i':
-			if (opts & OPT_INVERT) fatal("-%c has already been set", 'i');
-			opts |= OPT_INVERT;
-			break;
 		case '?':
-			fatal("usage: %s [number] [-l] [-a] [-v] [-i]", argv[0]);
+			printf("specify -h for help\n");
+			exit(EXIT_FAILURE);
+		case 'h':
+			printf(
+				"%s: a tool for turning on/off CPU threads\n"
+				"USAGE: %s [integer] [-l] [-a] [-v] [-i] [-h]\n"
+				"ARGUMENTS:\n"
+				"\t-l : List cores after executing the command. May be specified without integer.\n"
+				"\t-a : Writes to all cores, regardless of their state.\n"
+				"\t-v : Print the cores that are written. (implies -l)\n"
+				"\t-i : Instead of the given number.\n"
+				"\t-h : Shows this dialogue.\n",
+				argv[0], argv[0]);
+			exit(EXIT_SUCCESS);
 		}
 	}
 
 	if (optind < argc) {
+		char *end;
 		char *num = argv[optind];
-		*ncpus = atoi(num);
+		*ncpus = strtol(num, &end, 0);
-	} else if (opts & OPT_LIST_CORES) {
+		if (errno || end == num || *end != '\0')
-		*ncpus = -1;
+			fatal("failed to parse numeric value from string '%s'", num);
-	} else
+	} else if (!(opts & OPT_LIST_CORES))
 		fatal("must execute with either a number or [-l]");
 
 	return opts;

src/opts.h

@@ -1,6 +1,8 @@
 #pragma once
 #include <stdint.h>
 
+#include "util/intdef.h"
+
 enum opt {
 	OPT_LIST_CORES = 1, // option that lists the total amount of cores that are set
 	OPT_SET_ALL = 2,    // option to set all cores, regardless of their assumed state
@@ -8,4 +10,7 @@ enum opt {
 	OPT_INVERT = 8,     // 'num' now represents the amount of cores to disable
 };
 
-uint8_t getoptions(int32_t, char *const *, int32_t *);
+/* acquires the options given by the user through arguments.
+ * returns the bitmap of these options.
+ * `ncpus` is set to `-1`, or the amount of CPUs that the user requested to enable.*/
+u8 getoptions(int argc, char *const *argv, int *ncpus);