eval and execute: Automatically skips over empty commands (those that parse command interprets as empty lists)

src/fsh.nim

@@ -120,7 +120,8 @@ proc readCommand(strm: Stream): string =
       of '\\':
         result.add("\\")
         result.add(strm.readChar())
-      of '\n', '\r', ';': break
+      of '\n', '\r', ';':
+        break
       else: result.add(c)
 
 # readVariable reads a variable
@@ -168,6 +169,7 @@ proc substitute(strm: Stream, delim=";\p"): string =
       of '\\':
         result.add(strm.readChar())
       of '$': result.add(strm.readVariable.evalVariable)
+      of ';', '\n', '\r': break
       else:
         result.add(c)
 
@@ -189,9 +191,13 @@ proc parseCommand(cmd: string): seq[string] =
         newitem.add(strm.readSubstitution.newStringStream.substitute)
       of '$': result.add(strm.readVariable.evalVariable)
       of ' ':
+        if (result == @[]) and (newitem == ""): continue
         result.add(newitem)
         newitem = ""
         discard strm.skipSpaces()
+      of ';', '\n', '\r':
+        result.add(newitem)
+        break
       else: newitem.add(c)
 
 # runBuiltin runs a shell builtin
@@ -239,26 +245,38 @@ proc runBuiltin(builtin: string, args: openArray[string]): string =
 
 # executes executes the command. For now it involves catting the command and printing it
 proc execute(cmd: string): int =
-  let parsed = cmd.parseCommand
-  let progname = parsed[0]
-  let args = parsed[1..parsed.high]
-  if progname in builtins:
-    stdout.write(runBuiltin(progname, args))
-    return 0
-  let ps = startProcess(progname, args=args, options={poUsePath, poParentStreams})
-  result =  ps.waitForExit
-  ps.close
+  let strm=cmd.newStringStream
+  while not strm.atEnd:
+    let parsed = strm.readCommand.parseCommand
+    if parsed == @[]:
+      continue
+    let progname = parsed[0]
+    let args = parsed[1..parsed.high]
+    if progname in builtins:
+      stdout.write(runBuiltin(progname, args))
+      result = 0
+      continue
+    let ps = startProcess(progname, args=args, options={poUsePath, poParentStreams})
+    result =  ps.waitForExit
+    ps.close
+  strm.close
 
 # eval evaluates the given string
 proc eval(cmd: string): string =
-  let parsed = cmd.parseCommand
-  let progname=parsed[0]
-  let args = parsed[1..parsed.high]
-  if progname in builtins:
-    return runBuiltin(progname, args)
-  let ps = startProcess(progname, args=args, options={poUsePath})
-  result=ps.outputStream.readAll
-  ps.close
+  let strm=cmd.newStringStream
+  while not strm.atEnd():
+    let parsed = strm.readCommand.parseCommand
+    if parsed == @[]:
+      continue
+    let progname=parsed[0]
+    let args = parsed[1..parsed.high]
+    if progname in builtins:
+      result = runBuiltin(progname, args)
+      continue
+    let ps = startProcess(progname, args=args, options={poUsePath})
+    result=ps.outputStream.readAll
+    ps.close
+  strm.close
 
 when isMainModule:
   let stdinstrm = stdin.newFileStream