From ed90d39cd782f2491754bfc67f05247f521e9e59 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Sat, 25 Jan 2020 12:16:45 +0100
Subject: [PATCH] Shell: Allow empty tokens if enclosed in single or double
 quotes

Previously the shell parser would discard empty tokens. We now allow
them when they are enclosed in quotes (either '' or "")

This means that a command like _echo ""_ will actually pass an empty
string to /bin/echo in argv[1] now.
---
 Shell/Parser.cpp | 8 ++++----
 Shell/Parser.h   | 3 ++-
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/Shell/Parser.cpp b/Shell/Parser.cpp
index e08aa054f2..9fcc1a2683 100644
--- a/Shell/Parser.cpp
+++ b/Shell/Parser.cpp
@@ -29,9 +29,9 @@
 #include <unistd.h>
 #include <ctype.h>
 
-void Parser::commit_token()
+void Parser::commit_token(AllowEmptyToken allow_empty)
 {
-    if (m_token.is_empty())
+    if (allow_empty == AllowEmptyToken::No && m_token.is_empty())
         return;
     if (m_state == InRedirectionPath) {
         m_redirections.last().path = String::copy(m_token);
@@ -239,7 +239,7 @@ Vector<Command> Parser::parse()
             break;
         case State::InSingleQuotes:
             if (ch == '\'') {
-                commit_token();
+                commit_token(AllowEmptyToken::Yes);
                 m_state = State::Free;
                 break;
             }
@@ -247,7 +247,7 @@ Vector<Command> Parser::parse()
             break;
         case State::InDoubleQuotes:
             if (ch == '\"') {
-                commit_token();
+                commit_token(AllowEmptyToken::Yes);
                 m_state = State::Free;
                 break;
             }
diff --git a/Shell/Parser.h b/Shell/Parser.h
index fb516d95b1..06950e02ff 100644
--- a/Shell/Parser.h
+++ b/Shell/Parser.h
@@ -67,7 +67,8 @@ public:
     Vector<Command> parse();
 
 private:
-    void commit_token();
+    enum class AllowEmptyToken { No, Yes };
+    void commit_token(AllowEmptyToken = AllowEmptyToken::No);
     void commit_subcommand();
     void commit_command();
     void do_pipe();