Variables: 2 dollarsignsin a row are equal to a single dollarsign now

src/fsh.nim

@@ -18,12 +18,13 @@ for k, v in envPairs():
   envVariables[k]=v
 
 # list of builtin commands
-let builtins: array[5, string] = [
+let builtins: array[6, string] = [
 "set",
 "setenv",
 "echo",
 "exit",
 "if",
+"cd",
 ]
 
 # Exception types
@@ -178,6 +179,7 @@ proc readVariable(strm: Stream): string =
       result.add(strm.readSubstitution())
     of ']', '}':
       stderr.write("Unexpected " & c & ".\n")
+    of '$': result = "$"
     else:
       result.add(c)
       while not strm.atEnd():
@@ -188,6 +190,7 @@ proc readVariable(strm: Stream): string =
 
 # evalVariable finds a value of a variable
 proc evalVariable(vari: string): string =
+  if vari == "$": return "$"
   if shellVariables.hasKey(vari):
     result=shellVariables[vari]
   elif envVariables.hasKey(vari):
@@ -304,7 +307,23 @@ proc runBuiltin(builtin: string, args: openArray[string]): (string, int) =
           i.inc
           i.inc
           continue
-    
+    of "cd":
+      try:
+        if args.len == 0:
+          shellVariables["LASTPWD"] = getCurrentDir()
+          setCurrentDir(getHomeDir())
+          return ("", 0)
+        else:
+          if args[0] == "-":
+            let LASTPWD = getCurrentDir()
+            setCurrentDir(shellVariables["LASTPWD"])
+            shellVariables["LASTPWD"] = LASTPWD
+            return ("", 0)
+          shellVariables["LASTPWD"] = getCurrentDir()
+          setCurrentDir(args[0])
+          return ("", 0)
+      except OsError as e:
+        raise newShellCommandException("No such directory", "cd")
     else:
       raise newShellCommandException("No such builtin implemented", builtin)
 
@@ -354,9 +373,13 @@ when isMainModule:
   # ctrlc handler
   setControlCHook(ctrlc)
   let stdinstrm = stdin.newFileStream
+  # Set the default prompt
+  shellVariables["PROMPT"] = "$PWD \\$"
+  stdout.write(shellVariables["PROMPT"].newStringStream.substitute)
   while not stdinstrm.atEnd():
     try:
       discard stdinstrm.readCommand.execute
+      stdout.write(shellVariables["PROMPT"].newStringStream.substitute)
     except ShellError, ShellCommandError, ShellVariableError:
       let e = getCurrentException()
       stderr.write(e.msg, "\n")