feat: also modularizing main

Makefile

@@ -1,4 +1,4 @@
-.PHONY: all clean
+.PHONY: all
 
 all: out out/sh
 

src/main.c

@@ -1,15 +1,29 @@
 #include <stdio.h>
 #include <stdlib.h>
-#include <string.h>
+
+#include "reader.h"
 
 int main() {
+  /*
   size_t buffer_size;
   size_t initial_buffer_size = 64;
   char *input_buffer;
   char *initial_buffer_position;
   unsigned int how_many_characters_to_read;
+  */
+  char *input_line;
 
   while (1) {
+    printf("$ ");
+    input_line = read_a_line(stdin);
+    if (input_line == NULL) {
+      return 0;
+    }
+
+    printf("command: '%s'\n", input_line);
+
+    free(input_line);
+    /*
     buffer_size = initial_buffer_size;
     how_many_characters_to_read = buffer_size + 1;
     input_buffer = malloc(how_many_characters_to_read);
@@ -32,5 +46,6 @@ int main() {
     printf("%s", input_buffer);
 
     free(input_buffer);
+    */
   }
 }

src/reader.c

@@ -0,0 +1,33 @@
+#include "reader.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+char *read_a_line(FILE *file_to_read) {
+  size_t initial_buffer_size = 64;
+  size_t buffer_size = initial_buffer_size;
+  unsigned int how_many_characters_to_read = buffer_size + 1;
+  char *input_buffer = malloc(how_many_characters_to_read);
+  char *initial_buffer_position = input_buffer;
+
+  while (fgets(input_buffer, how_many_characters_to_read, file_to_read) !=
+             NULL &&
+         input_buffer[strlen(input_buffer) - 1] != '\n') {
+    size_t new_buffer_size = buffer_size * 2;
+    if (buffer_size != initial_buffer_size) {
+      how_many_characters_to_read = buffer_size + 1;
+    }
+    input_buffer = realloc(initial_buffer_position, new_buffer_size + 1);
+    initial_buffer_position = input_buffer;
+    input_buffer += buffer_size;
+    buffer_size = new_buffer_size;
+  }
+  input_buffer = initial_buffer_position;
+
+  if (!feof(file_to_read)) {
+    return input_buffer;
+  } else {
+    return NULL;
+  }
+}

src/reader.h

@@ -0,0 +1,8 @@
+#ifndef READER_H
+#define READER_H
+
+#include <stdio.h>
+
+char *read_a_line(FILE *file_to_read);
+
+#endif /* READER_H */