added cli parsing functions

makefile

@@ -22,3 +22,11 @@ clean:
 .PHONY: uninstall
 uninstall:
 	rm /usr/local/bin/ics_analyzer
+
+.PHONY: test
+test:
+	./a.out
+	@echo
+	./a.out -h
+	@echo
+	./a.out -f tests/calendar.ics

src/cli_arg_parsing.c

@@ -0,0 +1,41 @@
+#include "cli_arg_parsing.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+
+void usage() {
+  printf ("-h\tprint this help\n");
+  printf ("-f\tspecify ics file path\n");
+  exit(0);
+}
+
+void get_cli_args(int argc, char **argv, char **file_name) {
+  int opt = 0;
+
+  memset(file_name, '\0', strlen(*file_name));
+
+  if (argc < 2) {
+    char *home = getenv("HOME");
+    *file_name = home;
+
+    if (home != NULL) {
+      strcat(*file_name, "/.local/share/evolution/calendar/system/calendar.ics");
+    } else {
+      printf ("Environment variable HOME is not set.\n");
+      exit(1);
+    }
+    return;
+  }
+
+  while ((opt = getopt(argc, argv, "f:h")) != -1) {
+    switch(opt) {
+      case 'f':
+      *file_name = optarg;
+      break;
+      case 'h':
+      usage();
+    }
+  }
+}
+

src/cli_arg_parsing.h

@@ -0,0 +1,5 @@
+#pragma once
+
+void usage();
+
+void get_cli_args(int argc, char **argv, char **file_name);

src/main.c

@@ -1,3 +1,4 @@
+#include "cli_arg_parsing.h"
 #include "date_time_handling.h"
 #include "list_handling.h"
 #include "cut_string.h"
@@ -12,21 +13,13 @@
 #include <string.h>
 #include <limits.h>
 
-int main() {
-	//const char ICS_PATH[] = "tests/calendar.ics";
-	char *ICS_PATH;
-	char *HOME = getenv("HOME");
-
-	if (HOME != NULL) {
-		ICS_PATH = strcat(HOME, "/.local/share/evolution/calendar/system/calendar.ics");
-	} else {
-		printf ("Environment variable HOME is not set.\n");
-		return 1;
-	}
+int main(int argc, char **argv) {
+  char *ics_path = "";
+  get_cli_args(argc, argv, &ics_path);
 
 	char my_line[4096] = "";
 
-	int myfd = open(ICS_PATH, O_RDONLY);
+	int myfd = open(ics_path, O_RDONLY);
 	if (myfd == -1) {
 		perror ("Error opening file");
 		return 1;