i/o redirection in sh

better parsing of sh commands (copied from jos sh)
cat: read from 1 if no args
sbrk system call, but untested
getpid system call
moved locks in keyboard intr, but why do we get intr w. null characters from keyboard?

1 files changed, 272 insertions, 28 deletions

diff --git a/sh.c b/sh.c
index 9e0cb3f..2f2d297 100644
--- a/sh.c
+++ b/sh.c
@@ -4,52 +4,296 @@
 #include "fs.h"
 #include "fcntl.h"
 
-char *args[100];
-void parse(char buf[]);
+#define BUFSIZ  512
+#define MAXARGS  10
+#define MAXNODE 2
+
+// only allocate nodes for i/o redir; at some point we may have to build a 
+// a real parse tree.
+struct node {
+  int token;
+  char *s;
+};
+struct node list[MAXNODE];
+int nextnode;
+
+char buf[BUFSIZ];
+char *argv[MAXARGS];
+char argv0buf[BUFSIZ];
+int argc;
+
+int debug = 1;
+
+int parse(char *s);
+void runcmd(void);
+int ioredirection(void);
+int gettoken(char *s, char **token);
+int _gettoken(char *s, char **p1, char **p2);
+void addnode(int token, char *s);
 
 int
 main(void)
 {
-  char buf[128];
-  int pid;
-
   while(1){
     puts("$ ");
     memset (buf, '\0', sizeof(buf));
     gets(buf, sizeof(buf));
-    if(buf[0] == '\0')
+    if (parse(buf) < 0)
       continue;
-    pid = fork();
-    if(pid == 0){
-      parse(buf);
-      if (buf[0] == 'c' && buf[1] == 'd' && buf[2] == '\0') {  // cd
-	chdir(&buf[3]);
-      } else {
-	exec(buf, args);
-	printf(1, "%s: not found\n", buf);
-	exit();
+    runcmd();
+  }
+}
+
+int 
+parse(char *s)
+{
+  char *t;
+  int c;
+
+  gettoken(s, 0);
+
+  argc = 0;
+  nextnode = 0;
+  while (1) {
+    switch ((c = gettoken(0, &t))) {
+
+    case 'w':	// Add an argument
+      if (argc == MAXARGS) {
+	printf(2, "too many arguments\n");
+	return -1;
       }
+      argv[argc++] = t;
+      break;
+			
+    case '<':	// Input redirection
+      // Grab the filename from the argument list
+      if (gettoken(0, &t) != 'w') {
+	printf(2, "syntax error: < not followed by word\n");
+	return -1;
+      }
+      addnode('<', t);
+      break;
+			
+    case '>':	// Output redirection
+      // Grab the filename from the argument list
+      if (gettoken(0, &t) != 'w') {
+	printf(2, "syntax error: > not followed by word\n");
+	return -1;
+      }
+      addnode('>', t);
+      break;
+
+    case 0:		// String is complete
+      return 0;
+			
+    default:
+      printf(2, "syntax error: bad return %d from gettoken", c);
+      return -1;
+			
     }
-    if(pid > 0)
-      wait();
   }
 }
 
+
 void
-parse(char buf[])
+runcmd(void)
+{
+  int i, r, pid;
+
+  // Return immediately if command line was empty.
+  if(argc == 0) {
+    if (debug)
+      printf(2, "EMPTY COMMAND\n");
+    return;
+  }
+
+  // Clean up command line.
+  // Read all commands from the filesystem: add an initial '/' to
+  // the command name.
+  // This essentially acts like 'PATH=/'.
+  if (argv[0][0] != '/') {
+    argv0buf[0] = '/';
+    strcpy(argv0buf + 1, argv[0]);
+    argv[0] = argv0buf;
+  }
+  argv[argc] = 0;
+	
+  // Print the command.
+  if (debug) {
+    printf(2, "[%d] SPAWN:", getpid());
+    for (i = 0; argv[i]; i++)
+      printf(2, " %s", argv[i]);
+    for (i = 0; i < nextnode; i++) {
+      printf(2, "%c %s", list[i].token, list[i].s);
+    }
+    printf(2, "\n");
+  }
+
+  if (strcmp(argv[0], "/cd") == 0) {
+    if (debug) printf (2, "/cd %s is build in\n", argv[1]);
+    chdir(argv[1]);
+    return;
+  }
+
+  pid = fork();
+  if (pid == 0) {
+    if (ioredirection() < 0)
+      exit();
+    if ((r = exec(argv0buf, (char**) argv)) < 0) {
+      printf(2, "exec %s: %d\n", argv[0], r);
+      exit();
+    }
+  }
+
+  if (pid > 0) {
+    if (debug)
+      printf(2, "[%d] WAIT %s\n", getpid(), argv[0]);
+    wait();
+    if (debug)
+      printf(2, "[%d] wait finished\n", getpid());
+  }
+}
+
+int
+ioredirection(void)
 {
-  int j = 1;
-  int i;
-  args[0] = buf;
-  for (i = 0; buf[i] != '\0'; i++) {
-    if (buf[i] == ' ') {
-      buf[i] = '\0';
-      args[j++] = buf + i + 1;
-      if (j >= 100) {
-	printf(2, "too many args\n");
+  int i, fd, dfd;
+
+  for (i = 0; i < nextnode; i++) {
+    switch (list[i].token) {
+    case '<':
+      if ((fd = open(list[i].s, O_RDONLY)) < 0) {
+	printf(2, "failed to open %s for read: %d", list[i].s, fd);
+	return -1;
+      }
+
+      if (debug)
+	printf(2, "redirect 0 from %s\n", list[i].s);
+
+      close(0);
+      if ((dfd = dup(fd)) < 0)
+	printf(2, "dup failed\n");
+      if (debug)
+	printf(2, "dup returns %d\n", dfd);
+      close(fd);
+      break;
+    case '>':
+      if ((fd = open(list[i].s, O_WRONLY|O_CREATE)) < 0) {
+	printf(2, "failed to open %s for write: %d", list[i].s, fd);
 	exit();
       }
+
+      if (debug)
+	printf(2, "redirect 1 to %s\n", list[i].s);
+
+      if (close(1) < 0)
+	printf(2, "close 1 failed\n");
+      if ((dfd = dup(fd)) < 0)
+	printf(2, "dup failed\n");
+      if (debug)
+	printf(2, "dup returns %d\n", dfd);
+      close(fd);
+      break;
     }
   }
-  args[j] = '\0';
+  return 0;
+}
+
+void
+addnode(int token, char *s)
+{
+  if (nextnode >= MAXNODE) {
+    printf(2, "addnode: ran out of nodes\n");
+    return;
+  }
+    
+  list[nextnode].token = token;
+  list[nextnode].s = s;
+  nextnode++;
+}
+
+
+// gettoken(s, 0) prepares gettoken for subsequent calls and returns 0.
+// gettoken(0, token) parses a shell token from the previously set string,
+// null-terminates that token, stores the token pointer in '*token',
+// and returns a token ID (0, '<', '>', '|', or 'w').
+// Subsequent calls to 'gettoken(0, token)' will return subsequent
+// tokens from the string.
+
+int
+gettoken(char *s, char **p1)
+{
+  static int c, nc;
+  static char* np1, *np2;
+
+  if (s) {
+    nc = _gettoken(s, &np1, &np2);
+    return 0;
+  }
+  c = nc;
+  *p1 = np1;
+  nc = _gettoken(np2, &np1, &np2);
+  return c;
 }
+
+
+// Get the next token from string s.
+// Set *p1 to the beginning of the token and *p2 just past the token.
+// Returns
+//	0 for end-of-string;
+//	< for <;
+//	> for >;
+//	| for |;
+//	w for a word.
+//
+// Eventually (once we parse the space where the \0 will go),
+// words get nul-terminated.
+#define WHITESPACE " \t\r\n"
+#define SYMBOLS "<|>&;()"
+
+int
+_gettoken(char *s, char **p1, char **p2)
+{
+  int t;
+
+  if (s == 0) {
+    if (debug > 1)
+      printf(2, "GETTOKEN NULL\n");
+    return 0;
+  }
+
+  if (debug > 1)
+    printf(2, "GETTOKEN: %s\n", s);
+
+  *p1 = 0;
+  *p2 = 0;
+
+  while (strchr(WHITESPACE, *s))
+    *s++ = 0;
+  if (*s == 0) {
+    if (debug > 1)
+      printf(2, "EOL\n");
+    return 0;
+  }
+  if (strchr(SYMBOLS, *s)) {
+    t = *s;
+    *p1 = s;
+    *s++ = 0;
+    *p2 = s;
+    if (debug > 1)
+      printf(2, "TOK %c\n", t);
+    return t;
+  }
+  *p1 = s;
+  while (*s && !strchr(WHITESPACE SYMBOLS, *s))
+    s++;
+  *p2 = s;
+  if (debug > 1) {
+    t = **p2;
+    **p2 = 0;
+    printf(2, "WORD: %s\n", *p1);
+    **p2 = t;
+  }
+  return 'w';
+}
+