Add horrible code

smallsh/main.c

@@ -1,25 +1,54 @@
 #include "main.h"
 
+volatile sig_atomic_t stop_flag = 0;
+int stop_msg = 0;
+
 int main() {
 
+  /*
+  struct sigaction sa;
+    sa.sa_handler = sigstop_handle;
+    sa.sa_flags = 0;
+    sigemptyset(&sa.sa_mask);
+    */
+
+  signal(SIGINT, sigint_handle);
+  signal(SIGTSTP, sigstop_handle);
+
   int status = 0;
   size_t input_size = 2048;
   size_t getline_len;
   char* input = malloc(sizeof(char) * input_size);
 
   while(1) {
+
+    clean_children();
+
+    //signal handling
+    if(stop_msg) {
+      if(stop_flag) 
+        printf("Entering Stop Mode: Background Processes Do Not Work (&)\n");
+      else 
+        printf("Exiting Stop Mode: Background Processes Now Work (&)\n");
+      stop_msg = 0;
+    }
+
+
     printf(": ");
     fflush(stdout);
     getline_len = getline(&input, &input_size, stdin);
     input[getline_len - 1] = '\0';
 
+    expand_dollar(input, input_size);
+
     // Ignore whitespace or comments
-    if(input == NULL ||
+    if(input[0] == '\0' ||
        input[0] == '#') {
       continue;
     }
 
 
+
     char*** array = malloc(sizeof(char**));
     int num_strings = input_format(input, input_size, array);
 
@@ -73,13 +102,95 @@ int run_command(char*** array, int num_array) {
   char* comb_string = malloc(sizeof(char) * 100);
   sprintf(comb_string, "/usr/bin/");
   strcat(comb_string, (*array)[0]);
+
+
+  //Check to see if the process is ran in the background
+  int background = 0; 
+  if(!strncmp("&", (*array)[num_array - 1], 1)) {
+    if(!stop_flag)
+      background = 1;
+    (*array)[num_array - 1] = NULL;
+  }
+
+  // Check to see if the process has output redirected
+  int redirect_o = 0;
+  char* redirect_o_str = NULL;
+  for(int i = 0; i < num_array; i++) {
+
+    if((*array)[i] == NULL)
+      continue;
+
+    if(!strncmp((*array)[i], ">", 1)) {
+      redirect_o = 1;
+      redirect_o_str = (*array)[i+1];
+
+      (*array)[i] = NULL;
+      (*array)[i+1] = NULL;
+
+      break;
+    }
+  }
+
+  sterilize_array(array, num_array);
+
+  // Check to see if the process has input redirected
+  int redirect_i = 0;
+  char* redirect_i_str = NULL;
+  for(int i = 0; i < num_array; i++) {
+
+    if((*array)[i] == NULL)
+      continue;
+
+    if(!strncmp((*array)[i], "<", 1)) {
+      redirect_i = 1;
+      redirect_i_str = (*array)[i+1];
+
+      (*array)[i] = NULL;
+      (*array)[i+1] = NULL;
+
+      break;
+    }
+  }
+
+  sterilize_array(array, num_array);
+
   int f = fork();
   pid_t pid;
-  if(!f) 
+  if(!f) {
+    if(redirect_o) {
+      int fd = open(redirect_o_str, O_WRONLY | O_CREAT, 0666);
+      dup2(fd, STDOUT_FILENO);
+      dup2(fd, STDERR_FILENO);
+
+    }
+    else if(background) {
+      int fd = open("/dev/null", O_WRONLY, 0666);
+      //Direct to dev null
+      dup2(fd, STDOUT_FILENO);
+      dup2(fd, STDERR_FILENO);
+    }
+
+    if(redirect_i) {
+      int fd = open(redirect_i_str, O_RDONLY);
+      dup2(fd, STDIN_FILENO);
+    }
+    else if(background) {
+      int fd = open("/dev/null", O_RDONLY);
+      dup2(fd, STDIN_FILENO);
+    }
+
     pid = execv(comb_string, (*array));
 
+    perror(comb_string);
+    exit(1);
+  }
+  else if(background){
+    printf("background pid is %d\n", f);
+  }
+
   int status;
-  waitpid(pid, &status, 0);
+  if(!background)
+    waitpid(f, &status, 0);
 
   free(comb_string);
 
@@ -88,5 +199,67 @@ int run_command(char*** array, int num_array) {
 }
 
 
+void expand_dollar(char* input, size_t input_size) {
 
+  char pid[20];
+  int pid_size = sprintf(pid, "%d", getpid());
+  char* buffer = malloc(sizeof(char*) * (pid_size + input_size + 1));
 
+  char* dollar;
+
+  dollar = strstr(input, "$$");
+  while(dollar != NULL) {
+
+  dollar[0] = '%';
+  dollar[1] = 's';
+  sprintf(buffer, input, pid);
+  strcpy(input, buffer);
+  dollar = strstr(input, "$$");
+  }
+}
+
+void sterilize_array(char*** array, size_t num_array) {
+
+  for(int i = 0; i < num_array; i++) {
+
+    //check to see if it can be the end of the array
+    if((*array)[i] == NULL) {
+      int is_end = 1;
+      //check if there is any more non-null values in the array
+      for(int j = i; j < num_array; j++) {
+        if((*array)[j])
+          is_end = 0;
+      }
+
+      if(!is_end) {
+
+        //shift the array by 1 bit
+        for(int j = i; j < num_array; j++) {
+          (*array)[j] = (*array)[j+1];
+
+        }
+      }
+    }
+  }
+}
+
+void sigint_handle() {
+}
+
+void sigstop_handle(int n) {
+  stop_flag = !stop_flag;
+  stop_msg = !stop_msg;
+}
+
+void clean_children() {
+
+  // Clean up any child process that has not been cleaned
+  int pid = 43110;
+  while(pid >0) {
+    int status;
+    pid = waitpid(0, &status, WNOHANG);
+
+    if(pid > 0)
+      printf("\nbackground pid %d is done: exit value %d\n", pid, WEXITSTATUS(status));
+  }
+}

smallsh/main.h

@@ -7,9 +7,16 @@
 #include "string.h"
 #include "unistd.h"
 #include "sys/wait.h"
+#include "fcntl.h"
+#include "signal.h"
 
 int input_format(char*, size_t, char***);
 void inbuilt_cd(char*);
 int run_command(char***, int);
+void expand_dollar(char*, size_t);
+void sterilize_array(char***, size_t);
+void sigint_handle();
+void sigstop_handle();
+void clean_children();
 
 #endif