From 326e62862c790fac79e412263392680ee5628874 Mon Sep 17 00:00:00 2001
From: alistair <alistair@topost.net>
Date: Mon, 25 Nov 2019 15:44:26 +1000
Subject: [PATCH] support cd

---
 builtins.c |  0
 builtins.h |  0
 main.c     | 40 ++++++++++++++++++++++++++++++++++++----
 run.c      | 18 +++++++++---------
 run.h      |  9 +++------
 5 files changed, 48 insertions(+), 19 deletions(-)
 create mode 100644 builtins.c
 create mode 100644 builtins.h

diff --git a/builtins.c b/builtins.c
new file mode 100644
index 0000000..e69de29
diff --git a/builtins.h b/builtins.h
new file mode 100644
index 0000000..e69de29
diff --git a/main.c b/main.c
index 6b6ef29..0d8827e 100644
--- a/main.c
+++ b/main.c
@@ -1,14 +1,19 @@
 #include <stdlib.h>
 #include <stdio.h>
 #include <stdbool.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <string.h>
+
 #include "error.h"
 #include "run.h"
 
-#define INITIALLINEBUFFER 80
+#define INITIAL_LINE_BUFFER 80
 #define INITIAL_WORD_SIZE 80
+#define NUM_BUILTINS 2
 
 int readline(FILE* in, char **out) {
-    int size_of_buffer = INITIALLINEBUFFER;
+    int size_of_buffer = INITIAL_LINE_BUFFER;
     char *buffer = calloc(size_of_buffer, sizeof(char));
     char character;
     int count = 0;
@@ -82,6 +87,28 @@ int split_string(char **sep_string[], int *num, char *string, char delim) {
     return ER_FAILURE;
 }
 
+int check_builtins(char *args[]) {
+    char *builtins[NUM_BUILTINS] = {
+        "cd",
+    };
+    
+     if (!strcmp(args[0], "cd")) {
+
+         if (args[1] == 0) {
+             chdir(getenv("HOME"));
+             return ER_SUCCESS;
+         }
+
+         if (args[2] != 0) {
+             return ER_FAILURE;
+         }
+
+         chdir(args[1]);
+    }
+
+    return ER_FAILURE;
+}
+
 int repl(void) {
     while (true) {
         char *line;
@@ -94,7 +121,13 @@ int repl(void) {
         int num_words;
 
         split_string(&sep_string, &num_words, line, ' ');
-        execute(stdin, stdout, sep_string);
+        pid_t child;
+
+        if (check_builtins(sep_string)) {
+            execute(stdin, stdout, sep_string, &child);
+        }
+
+        waitpid(child, NULL, 0);
 
         for (int i = 0; i < num_words; i++) {
             free(sep_string[i]);
@@ -104,7 +137,6 @@ int repl(void) {
     }
 }
 
-
 int main(int argc, char** argv) {
 
     char *chicken[] = {
diff --git a/run.c b/run.c
index 9b47d2f..00c64d6 100644
--- a/run.c
+++ b/run.c
@@ -1,11 +1,18 @@
 #include "run.h"
 
+/* Contains builtin functions and code for executing system programs */
+
+int change_dir(char *dir) {
+    return chdir(dir);
+}
+
+
 /* Fork and exec a command given in args taking input from in and sending 
  * output to out. The arguments array must end in a NULL. 
  *
  * Returns true on success or 1 on failure.
  */
-int execute(FILE *in, FILE *out, char *args[]) {
+int execute(FILE *in, FILE *out, char *args[], pid_t* child_ID) {
     int in_FD = fileno(in);
     int out_FD = fileno(out);
 
@@ -16,6 +23,7 @@ int execute(FILE *in, FILE *out, char *args[]) {
     }
 
     if (err) {  // parent
+        *child_ID = err;
         return ER_SUCCESS;
     } else {    // child
         dup2(in_FD, 0);
@@ -27,11 +35,3 @@ int execute(FILE *in, FILE *out, char *args[]) {
     return ER_SUCCESS;
 }
 
-int test_exec(void) {
-    char *arg[] = {"ls", "lah", 0};
-
-    execute(stdin, stdout, arg);
-
-    return 0;
-}
-
diff --git a/run.h b/run.h
index 4e3f57e..0adca76 100644
--- a/run.h
+++ b/run.h
@@ -8,11 +8,8 @@
 #ifndef RUNH
 #define RUNH
 
-/* Fork and exec a command given in args taking input from in and sending 
- * output to out. The arguments array must end in a NULL. 
- *
- * Returns true on success or 1 on failure.
- */
-int execute(FILE* in, FILE* out, char *args[]);
+int execute(FILE *in, FILE *out, char *args[], pid_t* child_ID); 
+
+int change_dir(char *dir); 
 
 #endif