Updated with builtin command support!

MahmoodKS · Jan 16, 2015 · 45a0026 · 45a0026
1 parent 540a381
commit 45a0026
Showing 1 changed file with 100 additions and 5 deletions.
diff --git a/src/main.c b/src/main.c
@@ -17,11 +17,87 @@
 #include <stdio.h>
 #include <string.h>
 
+/*
+  Function Declarations for builtin shell commands:
+ */
+int lsh_cd(char **args);
+int lsh_help(char **args);
+int lsh_exit(char **args);
+
+/*
+  List of builtin commands, followed by their corresponding functions.
+ */
+char *builtin_str[] = {
+  "cd",
+  "help",
+  "exit"
+};
+
+int (*builtin_func[]) (char **) = {
+  &lsh_cd,
+  &lsh_help,
+  &lsh_exit
+};
+
+int lsh_num_builtins() {
+  return sizeof(builtin_str) / sizeof(char *);
+}
+
+/*
+  Builtin function implementations.
+*/
+
+/**
+   @brief Bultin command: change directory.
+   @param args List of args.  args[0] is "cd".  args[1] is the directory.
+   @return Always returns 1, to continue executing.
+ */
+int lsh_cd(char **args)
+{
+  if (args[1] == NULL) {
+    fprintf(stderr, "lsh: expected argument to \"cd\"\n");
+  } else {
+    if (chdir(args[1]) != 0) {
+      perror("lsh");
+    }
+  }
+  return 1;
+}
+
+/**
+   @brief Builtin command: print help.
+   @param args List of args.  Not examined.
+   @return Always returns 1, to continue executing.
+ */
+int lsh_help(char **args)
+{
+  int i;
+  printf("Stephen Brennan's LSH\n");
+  printf("Type program names and arguments, and hit enter.\n");
+  printf("The following are built in:\n");
+
+  for (i = 0; i < lsh_num_builtins(); i++) {
+    printf("  %s\n", builtin_str[i]);
+  }
+
+  printf("Use the man command for information on other programs.\n");
+  return 1;
+}
+
+/**
+   @brief Builtin command: exit.
+   @param args List of args.  Not examined.
+   @return Always returns 0, to terminate execution.
+ */
+int lsh_exit(char **args)
+{
+  return 0;
+}
 
 /**
   @brief Launch a program and wait for it to terminate.
   @param args Null terminated list of arguments (including program).
-  @return 0
+  @return Always returns 1, to continue execution.
  */
 int lsh_launch(char **args)
 {
@@ -45,7 +121,25 @@ int lsh_launch(char **args)
     } while (!WIFEXITED(status) && !WIFSIGNALED(status));
   }
 
-  return 0;
+  return 1;
+}
+
+/**
+   @brief Execute shell built-in or launch program.
+   @param args Null terminated list of arguments.
+   @return 1 if the shell should continue running, 0 if it should terminate
+ */
+int lsh_execute(char **args)
+{
+  int i;
+
+  for (i = 0; i < lsh_num_builtins(); i++) {
+    if (strcmp(args[0], builtin_str[i]) == 0) {
+      return (*builtin_func[i])(args);
+    }
+  }
+
+  return lsh_launch(args);
 }
 
 #define LSH_RL_BUFSIZE 1024
@@ -146,16 +240,17 @@ void lsh_loop(void)
 {
   char *line;
   char **args;
+  int status;
 
-  while (1) {
+  do {
     printf("> ");
     line = lsh_read_line();
     args = lsh_split_line(line);
-    lsh_launch(args);
+    status = lsh_execute(args);
 
     free(line);
     lsh_free_args(args);
-  }
+  } while (status);
 }
 
 /**