Fixed all those make files

.gitignore

@@ -33,3 +33,4 @@
 *.dSYM/
 
 .idea/
+.vscode/

21st_century_c/first_compile/Makefile

@@ -0,0 +1,12 @@
+.PHONY: clean
+P=erf
+OBJECTS= erf.o
+CFLAGS = -g -Wall -O3
+LDLIBS=''
+CC=gcc
+
+$(P): $(OBJECTS)
+
+
+clean:
+	rm -f *.o $(P)

Makefile

@@ -0,0 +1,6 @@
+CLEANSUBDIRS ?= types structs static pointers hello headers functions file_io env_vars
+
+cleanall:
+	@for subdir in $(CLEANSUBDIRS); do \
+		(cd $$subdir && $(MAKE) clean) || exit 1; \
+	done

env_vars/Makefile

@@ -1,7 +1,11 @@
-P=
+P=env
 OBJECTS=
 CFLAGS = -g -Wall -O3 
 LDLIBS=
 CC=gcc
 
 $(P): $(OBJECTS)
+
+clean:
+	rm -f *.o $(P)
+	rm -rf env.dSYM/

env_vars/env.c

@@ -1,14 +1,18 @@
 #include <stdlib.h> //getenv, atoi
 #include <stdio.h>	//printf
 
-int main(){
+int main()
+{
 	// pointer to a char
-	char *repstext=getenv("reps");
+	char *repstext = getenv("reps");
+	// atoi reads in the string and converts it to a integer value.
+	// This is the tenary operator 'condition ? value_if_true : value_if_false'
 	int reps = repstext ? atoi(repstext) : 10;
 
 	char *msg = getenv("msg");
-	if (!msg) msg = "Hello.";
+	if (!msg)
+		msg = "Hello.";
 
-	for (int i=0; i< reps; i++)
+	for (int i = 0; i < reps; i++)
 		printf("%s\n", msg);
 }

file_io/Makefile

@@ -4,4 +4,4 @@ csv_writer:
 	gcc -o csv_writer csv_writer.c
 
 clean:
-	rm -f csv_writer
+	rm -f csv_writer *.csv

file_io/csv_writer.c

@@ -4,10 +4,11 @@
 
 #define FILE_EXTENSION ".csv"
 
+int main(int argc, char const *argv[])
+{
 
-int main(int argc, char const *argv[]){
-
-	if (argc <= 1){
+	if (argc <= 1)
+	{
 		fprintf(stderr, "Failed to provide a csv file\n");
 		exit(1);
 	}
@@ -15,8 +16,9 @@ int main(int argc, char const *argv[]){
 	size_t file_len = strlen(argv[1]);
 
 	/*char pointer of*/
-	char * FILE_NAME = malloc(file_len + 1);
-	if (FILE_NAME == NULL){
+	char *FILE_NAME = malloc(file_len + 1);
+	if (FILE_NAME == NULL)
+	{
 		fprintf(stderr, "Failed to allocate memory for file name!");
 		exit(1);
 	}
@@ -25,7 +27,8 @@ int main(int argc, char const *argv[]){
 	strcpy(FILE_NAME, argv[1]);
 
 	/*Returns a pointer to the location the substring if found*/
-	if (strstr(FILE_NAME, FILE_EXTENSION) == NULL ){
+	if (strstr(FILE_NAME, FILE_EXTENSION) == NULL)
+	{
 		fprintf(stderr, "What the fuck are you doing? That %s isn't a csv file!\n", FILE_NAME);
 		free(FILE_NAME);
 		FILE_NAME = 0;
@@ -35,9 +38,9 @@ int main(int argc, char const *argv[]){
 	char name[128], phone_number[13];
 	// puts(FILE_NAME);
 	FILE *_target_file = fopen(FILE_NAME, "a");
-	if (_target_file == NULL){
+	if (_target_file == NULL)
+	{
 		exit(1);
-
 	}
 
 	puts("Name: ");
@@ -46,7 +49,7 @@ int main(int argc, char const *argv[]){
 	scanf("%s", phone_number);
 
 	printf("Appending %s and %s to %s", name, phone_number, FILE_NAME);
-	fprintf(_target_file,"%s,%s\n", name, phone_number);
+	fprintf(_target_file, "%s,%s\n", name, phone_number);
 	fclose(_target_file);
 	/*clean up*/
 	free(FILE_NAME);

file_io/dirp.csv

@@ -1 +0,0 @@
-Margot,517-775-7040

functions/Makefile

@@ -0,0 +1,12 @@
+.PHONY: clean
+P=cube
+OBJECTS= cube.o
+CFLAGS = -g -Wall -O3
+LDLIBS=''
+CC=gcc
+
+$(P): $(OBJECTS)
+
+
+clean:
+	rm -f *.o $(P)

pointers/Makefile

@@ -1,5 +1,5 @@
 CFLAGS=-Wall -O3
-PROGRAMS=simple_pointer adv_pointer
+PROGRAMS=simple_pointer adv_pointer char_pointer
 
 all: $(PROGRAMS)
 
@@ -9,6 +9,9 @@ simple_pointer:
 adv_pointer:
 	gcc -o adv_pointer $(CFLAGS) adv_pointer.c
 
+char_pointer:
+	gcc -o char_pointer $(CFLAGS) char_pointer.c
+
 # NOT IMPLEMENTED
 #array_pointer:
 #	gcc -o array_pointer -Wall -O1 array_pointer.c

pointers/char_pointer.c

@@ -0,0 +1,33 @@
+#include <stdio.h>
+
+#define DOLLARS 0x24;
+
+// Example of function declaration. This is what the preprocessor does with the header files
+void set_to_y(char *p);
+
+int main()
+{
+    char my_char = 'a';
+    char *p_char;
+
+    p_char = &my_char;
+
+    printf("The value of *p_char is set to %c\n", *p_char);
+    set_to_y(p_char);
+
+    printf("Lets check the value of my_char: %c\n", my_char);
+    printf("You, know what I want to just muck with your memory directly\n");
+
+    //derefence the location and just set the byte we want
+    *p_char = DOLLARS;
+    printf("So all your bits now should show my_char as $ DOLLARS. Lets see: %c\n", my_char);
+
+    return 0;
+}
+
+// This is function definition
+void set_to_y(char *p)
+{
+    fprintf(stdout, "Setting the value at address %p from %c to y\n", &p, *p);
+    *p = 'y';
+}

types/Makefile

@@ -0,0 +1,12 @@
+.PHONY: clean
+P=types
+OBJECTS= types.o
+CFLAGS = -g -Wall -O3
+LDLIBS=''
+CC=gcc
+
+$(P): $(OBJECTS)
+
+
+clean:
+	rm -f *.o $(P)

types/types.c

@@ -3,8 +3,6 @@
 //Type definition
 typedef unsigned char byte;
 
-
-
 int main(int argc, char const *argv[])
 {
 	int i = 123;
@@ -30,7 +28,7 @@ int main(int argc, char const *argv[])
 
 	//we have to cast the result of sizeof because it returns a value whose size is large enough
 	//to hold a pointer value, but the fundamental types will never be that big so we cast
-	printf("The value of i: %d (%d) bytes\n", i, (int) sizeof(int));
+	printf("The value of i: %d (%d) bytes\n", i, (int)sizeof(int));
 	//this will tell us that int is 4 bytes and running in a 32 bit address space
 
 	return 0;