diff --git a/FishsFish.xcodeproj/project.pbxproj b/FishsFish.xcodeproj/project.pbxproj
index 320528b5a..e4987a9c0 100644
--- a/FishsFish.xcodeproj/project.pbxproj
+++ b/FishsFish.xcodeproj/project.pbxproj
@@ -28,14 +28,14 @@
 /* End PBXAggregateTarget section */
 
 /* Begin PBXBuildFile section */
+		D025C02A15D1FEA100B9DB63 /* completions in Resources */ = {isa = PBXBuildFile; fileRef = D025C02715D1FEA100B9DB63 /* completions */; };
+		D025C02B15D1FEA100B9DB63 /* functions in Resources */ = {isa = PBXBuildFile; fileRef = D025C02815D1FEA100B9DB63 /* functions */; };
+		D025C02C15D1FEA100B9DB63 /* tools in Resources */ = {isa = PBXBuildFile; fileRef = D025C02915D1FEA100B9DB63 /* tools */; };
 		D07A7D3C15A7A38100811FC6 /* builtin_scripts.cpp in Sources */ = {isa = PBXBuildFile; fileRef = D0F5E28215A7A32D00315DFF /* builtin_scripts.cpp */; };
 		D07B247315BCC15700D4ADB4 /* add-shell in Resources */ = {isa = PBXBuildFile; fileRef = D07B247215BCC15700D4ADB4 /* add-shell */; };
 		D07B247615BCC4BE00D4ADB4 /* install.sh in Resources */ = {isa = PBXBuildFile; fileRef = D07B247515BCC4BE00D4ADB4 /* install.sh */; };
 		D0C4FD9515A7D80700212EF1 /* config.fish in CopyFiles */ = {isa = PBXBuildFile; fileRef = D0C4FD9415A7D7EE00212EF1 /* config.fish */; };
 		D0C4FD9615A7D80C00212EF1 /* config.fish in CopyFiles */ = {isa = PBXBuildFile; fileRef = D0CBD580159EE48F0024809C /* config.fish */; };
-		D0CBD57B159EE4640024809C /* completions in CopyFiles */ = {isa = PBXBuildFile; fileRef = D0CBD578159EE4600024809C /* completions */; };
-		D0CBD57C159EE4640024809C /* functions in CopyFiles */ = {isa = PBXBuildFile; fileRef = D0CBD579159EE4600024809C /* functions */; };
-		D0CBD57D159EE4640024809C /* tools in CopyFiles */ = {isa = PBXBuildFile; fileRef = D0CBD57A159EE4600024809C /* tools */; };
 		D0CBD587159EF0E10024809C /* launch_fish.scpt in Resources */ = {isa = PBXBuildFile; fileRef = D0CBD586159EF0E10024809C /* launch_fish.scpt */; };
 		D0D02A67159837AD008E62BD /* complete.cpp in Sources */ = {isa = PBXBuildFile; fileRef = D0A0853713B3ACEE0099B651 /* complete.cpp */; };
 		D0D02A69159837B2008E62BD /* env.cpp in Sources */ = {isa = PBXBuildFile; fileRef = D0A0853A13B3ACEE0099B651 /* env.cpp */; };
@@ -121,9 +121,6 @@
 		D0F019F415A9772C0034B3B1 /* fish_pager in CopyFiles */ = {isa = PBXBuildFile; fileRef = D0D02AE415986537008E62BD /* fish_pager */; };
 		D0F019F615A977360034B3B1 /* set_color in CopyFiles */ = {isa = PBXBuildFile; fileRef = D0F019DC15A969970034B3B1 /* set_color */; };
 		D0F019F815A977AB0034B3B1 /* config.fish in CopyFiles */ = {isa = PBXBuildFile; fileRef = D0CBD580159EE48F0024809C /* config.fish */; };
-		D0F019F915A977AD0034B3B1 /* completions in CopyFiles */ = {isa = PBXBuildFile; fileRef = D0CBD578159EE4600024809C /* completions */; };
-		D0F019FA15A977AE0034B3B1 /* functions in CopyFiles */ = {isa = PBXBuildFile; fileRef = D0CBD579159EE4600024809C /* functions */; };
-		D0F019FB15A977B00034B3B1 /* tools in CopyFiles */ = {isa = PBXBuildFile; fileRef = D0CBD57A159EE4600024809C /* tools */; };
 		D0F019FD15A977CA0034B3B1 /* config.fish in CopyFiles */ = {isa = PBXBuildFile; fileRef = D0C4FD9415A7D7EE00212EF1 /* config.fish */; };
 		D0F01A0315A978910034B3B1 /* osx_fish_launcher.m in Sources */ = {isa = PBXBuildFile; fileRef = D0D02AFA159871B2008E62BD /* osx_fish_launcher.m */; };
 		D0F01A0515A978A10034B3B1 /* Foundation.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = D0CBD583159EEE010024809C /* Foundation.framework */; };
@@ -210,9 +207,6 @@
 			dstSubfolderSpec = 7;
 			files = (
 				D0C4FD9615A7D80C00212EF1 /* config.fish in CopyFiles */,
-				D0CBD57B159EE4640024809C /* completions in CopyFiles */,
-				D0CBD57C159EE4640024809C /* functions in CopyFiles */,
-				D0CBD57D159EE4640024809C /* tools in CopyFiles */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
@@ -261,9 +255,6 @@
 			dstSubfolderSpec = 1;
 			files = (
 				D0F019F815A977AB0034B3B1 /* config.fish in CopyFiles */,
-				D0F019F915A977AD0034B3B1 /* completions in CopyFiles */,
-				D0F019FA15A977AE0034B3B1 /* functions in CopyFiles */,
-				D0F019FB15A977B00034B3B1 /* tools in CopyFiles */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
@@ -280,6 +271,9 @@
 /* End PBXCopyFilesBuildPhase section */
 
 /* Begin PBXFileReference section */
+		D025C02715D1FEA100B9DB63 /* completions */ = {isa = PBXFileReference; lastKnownFileType = folder; name = completions; path = share/completions; sourceTree = "<group>"; };
+		D025C02815D1FEA100B9DB63 /* functions */ = {isa = PBXFileReference; lastKnownFileType = folder; name = functions; path = share/functions; sourceTree = "<group>"; };
+		D025C02915D1FEA100B9DB63 /* tools */ = {isa = PBXFileReference; lastKnownFileType = folder; name = tools; path = share/tools; sourceTree = "<group>"; };
 		D03EE83814DF88B200FC7150 /* lru.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = lru.h; sourceTree = "<group>"; };
 		D07B247215BCC15700D4ADB4 /* add-shell */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.script.sh; name = "add-shell"; path = "build_tools/osx_package_scripts/add-shell"; sourceTree = "<group>"; };
 		D07B247515BCC4BE00D4ADB4 /* install.sh */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.script.sh; name = install.sh; path = osx/install.sh; sourceTree = "<group>"; };
@@ -387,9 +381,6 @@
 		D0C4FD9415A7D7EE00212EF1 /* config.fish */ = {isa = PBXFileReference; lastKnownFileType = text; name = config.fish; path = etc/config.fish; sourceTree = "<group>"; };
 		D0C6FCC914CFA4B0004CE8AD /* autoload.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = autoload.cpp; sourceTree = "<group>"; };
 		D0C6FCCB14CFA4B7004CE8AD /* autoload.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = autoload.h; sourceTree = "<group>"; };
-		D0CBD578159EE4600024809C /* completions */ = {isa = PBXFileReference; lastKnownFileType = folder; name = completions; path = share/completions; sourceTree = "<group>"; };
-		D0CBD579159EE4600024809C /* functions */ = {isa = PBXFileReference; lastKnownFileType = folder; name = functions; path = share/functions; sourceTree = "<group>"; };
-		D0CBD57A159EE4600024809C /* tools */ = {isa = PBXFileReference; lastKnownFileType = folder; name = tools; path = share/tools; sourceTree = "<group>"; };
 		D0CBD580159EE48F0024809C /* config.fish */ = {isa = PBXFileReference; lastKnownFileType = text; name = config.fish; path = share/config.fish; sourceTree = "<group>"; };
 		D0CBD583159EEE010024809C /* Foundation.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = Foundation.framework; path = System/Library/Frameworks/Foundation.framework; sourceTree = SDKROOT; };
 		D0CBD586159EF0E10024809C /* launch_fish.scpt */ = {isa = PBXFileReference; lastKnownFileType = file; name = launch_fish.scpt; path = osx/launch_fish.scpt; sourceTree = "<group>"; };
@@ -608,10 +599,10 @@
 				D0CBD580159EE48F0024809C /* config.fish */,
 				D0C4FD9415A7D7EE00212EF1 /* config.fish */,
 				D07B247515BCC4BE00D4ADB4 /* install.sh */,
-				D0CBD578159EE4600024809C /* completions */,
-				D0CBD579159EE4600024809C /* functions */,
-				D0CBD57A159EE4600024809C /* tools */,
 				D0D02AA915985C0C008E62BD /* Info.plist */,
+				D025C02715D1FEA100B9DB63 /* completions */,
+				D025C02815D1FEA100B9DB63 /* functions */,
+				D025C02915D1FEA100B9DB63 /* tools */,
 			);
 			name = Resources;
 			sourceTree = "<group>";
@@ -813,6 +804,9 @@
 				D0CBD587159EF0E10024809C /* launch_fish.scpt in Resources */,
 				D07B247315BCC15700D4ADB4 /* add-shell in Resources */,
 				D07B247615BCC4BE00D4ADB4 /* install.sh in Resources */,
+				D025C02A15D1FEA100B9DB63 /* completions in Resources */,
+				D025C02B15D1FEA100B9DB63 /* functions in Resources */,
+				D025C02C15D1FEA100B9DB63 /* tools in Resources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
diff --git a/builtin.cpp b/builtin.cpp
index f910486c2..f9a42f979 100644
--- a/builtin.cpp
+++ b/builtin.cpp
@@ -155,7 +155,7 @@ static int builtin_stdin;
    should normally not be used - sb_out and friends are already
    configured to handle everything.
 */
-static io_data_t *real_io;
+static const io_chain_t *real_io;
 
 /**
    Counts the number of non null pointers in the specified array
@@ -2752,7 +2752,7 @@ static int builtin_contains( parser_t &parser, wchar_t ** argv )
 		switch( opt )
 		{
 			case 0:
-                assert(opt_index >= 0 && opt_index < sizeof long_options / sizeof *long_options);
+                assert(opt_index >= 0 && (size_t)opt_index < sizeof long_options / sizeof *long_options);
 				if(long_options[opt_index].flag != 0)
 					break;
 				append_format(stderr_buffer,
@@ -2878,7 +2878,7 @@ static int builtin_source( parser_t &parser, wchar_t ** argv )
 	
 	parse_util_set_argv( (argc>2)?(argv+2):(argv+1), wcstring_list_t());
 	
-	res = reader_read( fd, real_io );
+	res = reader_read( fd, real_io ? *real_io : io_chain_t() );
 		
 	parser.pop_block();
 		
@@ -3470,7 +3470,7 @@ static int builtin_breakpoint( parser_t &parser, wchar_t **argv )
 {
 	parser.push_block( BREAKPOINT );		
 	
-	reader_read( STDIN_FILENO, real_io );
+	reader_read( STDIN_FILENO, real_io ? *real_io : io_chain_t() );
 	
 	parser.pop_block();		
 	
@@ -3861,10 +3861,10 @@ static int internal_help( const wchar_t *cmd )
 }
 
 
-int builtin_run( parser_t &parser, const wchar_t * const *argv, io_data_t *io )
+int builtin_run( parser_t &parser, const wchar_t * const *argv, const io_chain_t &io )
 {
 	int (*cmd)(parser_t &parser, const wchar_t * const *argv)=0;
-	real_io = io;
+	real_io = &io;
 		
 	CHECK( argv, STATUS_BUILTIN_ERROR );
 	CHECK( argv[0], STATUS_BUILTIN_ERROR );
diff --git a/builtin.h b/builtin.h
index a34c83cbb..eee03b90c 100644
--- a/builtin.h
+++ b/builtin.h
@@ -135,7 +135,7 @@ int builtin_exists( const wcstring &cmd );
 
   \return the exit status of the builtin command
 */
-int builtin_run( parser_t &parser, const wchar_t * const *argv, io_data_t *io );
+int builtin_run( parser_t &parser, const wchar_t * const *argv, const io_chain_t &io );
 
 /** Returns a list of all builtin names */
 wcstring_list_t builtin_get_names(void);
diff --git a/builtin_set.cpp b/builtin_set.cpp
index 35dea7a12..c9b0b4b68 100644
--- a/builtin_set.cpp
+++ b/builtin_set.cpp
@@ -313,7 +313,7 @@ static void erase_values(wcstring_list_t &list, const std::vector<long> &indexes
     std::set<long>::const_reverse_iterator iter;
     for (iter = indexes_set.rbegin(); iter != indexes_set.rend(); iter++) {
         long val = *iter;
-        if (val > 0 && val <= list.size()) {
+        if (val > 0 && (size_t)val <= list.size()) {
             // One-based indexing!
             list.erase(list.begin() + val - 1);
         }
diff --git a/common.h b/common.h
index 05c795bb5..2028a5d28 100644
--- a/common.h
+++ b/common.h
@@ -135,9 +135,9 @@ extern const wchar_t *program_name;
 */
 #define FATAL_EXIT()											\
 	{															\
-		ssize_t exit_read_count;char exit_read_buff;			\
+		char exit_read_buff;			\
 		show_stackframe();										\
-		exit_read_count=read( 0, &exit_read_buff, 1 );			\
+		read( 0, &exit_read_buff, 1 );			\
 		exit_without_destructors( 1 );												\
 	}															\
 		
diff --git a/configure.ac b/configure.ac
index 3da41794d..ddb8a9158 100644
--- a/configure.ac
+++ b/configure.ac
@@ -39,6 +39,8 @@ AC_SUBST(XSEL_MAN)
 AC_SUBST(XSEL_BIN)
 AC_SUBST(XSEL_MAN_PATH)
 
+
+
 #
 # If needed, run autoconf to regenerate the configure file
 #
@@ -559,7 +561,7 @@ LIBS=$LIBS_COMMON
 # Check presense of various header files
 #
 
-AC_CHECK_HEADERS([getopt.h termio.h sys/resource.h term.h ncurses/term.h ncurses.h curses.h stropts.h siginfo.h sys/select.h sys/ioctl.h sys/termios.h libintl.h execinfo.h])
+AC_CHECK_HEADERS([getopt.h termio.h sys/resource.h term.h ncurses/term.h ncurses.h curses.h stropts.h siginfo.h sys/select.h sys/ioctl.h sys/termios.h libintl.h execinfo.h spawn.h])
 
 AC_CHECK_HEADER(
 	[regex.h],
diff --git a/env.cpp b/env.cpp
index 26658379a..387d50c24 100644
--- a/env.cpp
+++ b/env.cpp
@@ -101,6 +101,7 @@ struct var_entry_t
 typedef std::map<wcstring, var_entry_t*> var_table_t;
 
 bool g_log_forks = false;
+bool g_use_posix_spawn = false; //will usually be set to true
 
 
 /**
@@ -187,7 +188,11 @@ static null_terminated_array_t<char> export_array;
    Flag for checking if we need to regenerate the exported variable
    array
 */
-static bool has_changed = true;
+static bool has_changed_exported = true;
+static void mark_changed_exported()
+{
+    has_changed_exported = true;
+}
 
 /**
    This string is used to store the value of dynamically
@@ -257,7 +262,7 @@ static void start_fishd()
     }
     
     parser_t &parser = parser_t::principal_parser();
-	parser.eval( cmd, 0, TOP );
+	parser.eval( cmd, io_chain_t(), TOP );
 }
 
 /**
@@ -394,7 +399,7 @@ static void universal_callback( int type,
 	
 	if( str )
 	{
-		has_changed=true;
+		mark_changed_exported();
 		
         event_t ev = event_t::variable_event(name);
         ev.arguments.reset(new wcstring_list_t());
@@ -682,6 +687,10 @@ void env_init(const struct config_paths_t *paths /* or NULL */)
     /* Set g_log_forks */
     env_var_t log_forks = env_get_string(L"fish_log_forks");
     g_log_forks = ! log_forks.missing_or_empty() && from_string<bool>(log_forks);
+    
+    /* Set g_use_posix_spawn. Default to true. */
+    env_var_t use_posix_spawn = env_get_string(L"fish_use_posix_spawn");
+    g_use_posix_spawn = (use_posix_spawn.missing_or_empty() ? true : from_string<bool>(use_posix_spawn));
 }
 
 void env_destroy()
@@ -702,7 +711,7 @@ void env_destroy()
 		var_entry_t *entry = iter->second;	
 		if( entry->exportv )
 		{
-			has_changed = true;
+			mark_changed_exported();
 		}
 
 		delete entry;
@@ -741,12 +750,12 @@ int env_set(const wcstring &key, const wchar_t *val, int var_mode)
 {
     ASSERT_IS_MAIN_THREAD();
 	env_node_t *node = NULL;
-	bool has_changed_old = has_changed;
+	bool has_changed_old = has_changed_exported;
 	bool has_changed_new = false;
 	var_entry_t *e=0;	
 	int done=0;
     
-	int is_universal = 0;	
+	int is_universal = 0;
     
 	if( val && contains( key, L"PWD", L"HOME" ) )
 	{
@@ -935,7 +944,8 @@ int env_set(const wcstring &key, const wchar_t *val, int var_mode)
 			    node->exportv=1;
             }
             
-			has_changed = has_changed_old || has_changed_new;
+            if (has_changed_old || has_changed_new)
+                mark_changed_exported();
         }
         
     }
@@ -982,7 +992,7 @@ static int try_remove( env_node_t *n,
 
 		if( v->exportv )
 		{
-			has_changed = true;
+			mark_changed_exported();
 		}
         
 		n->env.erase(result);
@@ -1279,7 +1289,8 @@ void env_push( int new_scope )
 	
 	if( new_scope )
 	{
-		has_changed |= local_scope_exports(top);
+        if (local_scope_exports(top))
+            mark_changed_exported();
 	}
 	top = node;	
 
@@ -1307,7 +1318,8 @@ void env_pop()
 
 		if( killme->new_scope )
 		{
-			has_changed |= killme->exportv || local_scope_exports( killme->next );
+            if (killme->exportv || local_scope_exports( killme->next ))
+                mark_changed_exported();
 		}
 		
 		top = top->next;
@@ -1318,7 +1330,7 @@ void env_pop()
 			var_entry_t *entry = iter->second;	
 			if( entry->exportv )
 			{
-				has_changed = true;
+				mark_changed_exported();
 			}
 			delete entry;
 		}
@@ -1489,7 +1501,7 @@ static void update_export_array_if_necessary(bool recalc) {
 		env_universal_barrier();
 	}
 	
-	if( has_changed )
+	if( has_changed_exported )
 	{
 		std::map<wcstring, wcstring> vals;
 		size_t i;
@@ -1515,22 +1527,22 @@ static void update_export_array_if_necessary(bool recalc) {
         std::vector<std::string> local_export_buffer;
 		export_func(vals, local_export_buffer );
         export_array.set(local_export_buffer);
-		has_changed=false;
+		has_changed_exported=false;
 	}
 
 }
 
-char **env_export_arr( int recalc )
+char **env_export_arr( bool recalc )
 {
     ASSERT_IS_MAIN_THREAD();
-    update_export_array_if_necessary(recalc != 0);
+    update_export_array_if_necessary(recalc);
     return export_array.get();
 }
 
 void env_export_arr(bool recalc, null_terminated_array_t<char> &output)
 {
     ASSERT_IS_MAIN_THREAD();
-    update_export_array_if_necessary(recalc != 0);
+    update_export_array_if_necessary(recalc);
     output = export_array;
 }
 
diff --git a/env.h b/env.h
index bd597f1b9..2c32b6a08 100644
--- a/env.h
+++ b/env.h
@@ -165,7 +165,7 @@ void env_push( int new_scope );
 void env_pop();
 
 /** Returns an array containing all exported variables in a format suitable for execv. */
-char **env_export_arr( int recalc );
+char **env_export_arr( bool recalc );
 void env_export_arr(bool recalc, null_terminated_array_t<char> &result);
 
 /**
@@ -201,5 +201,7 @@ public:
 extern bool g_log_forks;
 extern int g_fork_count;
 
+extern bool g_use_posix_spawn;
+
 
 #endif
diff --git a/event.cpp b/event.cpp
index 619200edf..176bc0a0d 100644
--- a/event.cpp
+++ b/event.cpp
@@ -454,7 +454,7 @@ static void event_fire_internal( const event_t *event )
         parser_t &parser = parser_t::principal_parser();
 		parser.push_block( EVENT );
 		parser.current_block->state1<const event_t *>() = event;
-		parser.eval( buffer, 0, TOP );
+		parser.eval( buffer, io_chain_t(), TOP );
 		parser.pop_block();
 		proc_pop_interactive();					
 		proc_set_last_status( prev_status );
diff --git a/exec.cpp b/exec.cpp
index e20c48263..499250923 100644
--- a/exec.cpp
+++ b/exec.cpp
@@ -49,6 +49,7 @@
 #include "expand.h"
 #include "signal.h"
 
+
 #include "parse_util.h"
 
 /**
@@ -148,24 +149,25 @@ int exec_pipe( int fd[2])
 /**
    Check if the specified fd is used as a part of a pipeline in the
    specidied set of IO redirections.
+   This is called after fork().
 
    \param fd the fd to search for
-   \param io the set of io redirections to search in
+   \param io_chain the set of io redirections to search in
 */
-static int use_fd_in_pipe( int fd, io_data_t *io )
-{	
-	if( !io )
-		return 0;
-	
-	if( ( io->io_mode == IO_BUFFER ) || 
-		( io->io_mode == IO_PIPE ) )
-	{
-		if( io->param1.pipe_fd[0] == fd ||
-			io->param1.pipe_fd[1] == fd )
-			return 1;
-	}
-		
-	return use_fd_in_pipe( fd, io->next );
+static bool use_fd_in_pipe(int fd, const io_chain_t &io_chain )
+{
+    for (size_t idx = 0; idx < io_chain.size(); idx++)
+    {
+        const io_data_t *io = io_chain.at(idx);
+        if( ( io->io_mode == IO_BUFFER ) || 
+            ( io->io_mode == IO_PIPE ) )
+        {
+            if( io->param1.pipe_fd[0] == fd ||
+                io->param1.pipe_fd[1] == fd )
+                return true;
+        }
+    }
+    return false;
 }
 
 
@@ -177,13 +179,13 @@ static int use_fd_in_pipe( int fd, io_data_t *io )
    \param io the list of io redirections for this job. Pipes mentioned
    here should not be closed.
 */
-void close_unused_internal_pipes( io_data_t *io )
+void close_unused_internal_pipes( const io_chain_t &io )
 {
     /* A call to exec_close will modify open_fds, so be careful how we walk */
     for (size_t i=0; i < open_fds.size(); i++) {
         if (open_fds[i]) {
             int fd = (int)i;
-            if( !use_fd_in_pipe( fd, io) )
+            if( !use_fd_in_pipe(fd, io))
             {
                 debug( 4, L"Close fd %d, used in other context", fd );
                 exec_close( fd );
@@ -193,11 +195,24 @@ void close_unused_internal_pipes( io_data_t *io )
     }
 }
 
+void get_unused_internal_pipes(std::vector<int> &fds, const io_chain_t &io)
+{
+    for (size_t i=0; i < open_fds.size(); i++) {
+        if (open_fds[i]) {
+            int fd = (int)i;
+            if( !use_fd_in_pipe(fd, io))
+            {
+                fds.push_back(fd);
+            }
+        }
+    }
+}
+
 /**
    Returns the interpreter for the specified script. Returns NULL if file
    is not a script with a shebang.
  */
-static char *get_interpreter( const char *command, char *interpreter, size_t buff_size )
+char *get_interpreter( const char *command, char *interpreter, size_t buff_size )
 {
     // OK to not use CLO_EXEC here because this is only called after fork
 	int fd = open( command, O_RDONLY );
@@ -239,9 +254,8 @@ static void safe_launch_process( process_t *p, const char *actual_cmd, char **ar
 	
 //	debug( 1, L"exec '%ls'", p->argv[0] );
 
-	execve ( wcs2str(p->actual_cmd.c_str()), 
-		 argv,
-		 envv );
+    // Wow, this wcs2str call totally allocates memory
+	execve ( actual_cmd, argv, envv );
 	
 	err = errno;
 	
@@ -275,88 +289,8 @@ static void safe_launch_process( process_t *p, const char *actual_cmd, char **ar
 	}
 	
 	errno = err;
-	debug_safe( 0, "Failed to execute process '%s'. Reason:", actual_cmd );
-	
-	switch( errno )
-	{
-		
-		case E2BIG:
-		{
-			char sz1[128], sz2[128];
-			
-			long arg_max = -1;
-
-			size_t sz = 0;
-			char **p;
-			for(p=argv; *p; p++)
-			{
-				sz += strlen(*p)+1;
-			}
-			
-			for(p=envv; *p; p++)
-			{
-				sz += strlen(*p)+1;
-			}
-			
-            format_size_safe(sz1, sz);
-			arg_max = sysconf( _SC_ARG_MAX );
-			
-			if( arg_max > 0 )
-			{
-                format_size_safe(sz2, sz);
-                debug_safe(0, "The total size of the argument and environment lists %s exceeds the operating system limit of %s.", sz1, sz2);
-			}
-			else
-			{
-				debug_safe( 0, "The total size of the argument and environment lists (%s) exceeds the operating system limit.", sz1);
-			}
-			
-			debug_safe(0, "Try running the command again with fewer arguments.");			
-			exit_without_destructors(STATUS_EXEC_FAIL);
-			break;
-		}
-
-		case ENOEXEC:
-		{
-            /* Hope strerror doesn't allocate... */
-            const char *err = strerror(errno);
-            debug_safe(0, "exec: %s", err);
-			
-			debug_safe(0, "The file '%ls' is marked as an executable but could not be run by the operating system.", actual_cmd);
-			exit_without_destructors(STATUS_EXEC_FAIL);
-		}
-
-		case ENOENT:
-		{
-            char interpreter_buff[128] = {}, *interpreter;
-            interpreter = get_interpreter(actual_cmd, interpreter_buff, sizeof interpreter_buff);
-			if( interpreter && 0 != access( interpreter, X_OK ) )
-			{
-				debug_safe(0, "The file '%s' specified the interpreter '%s', which is not an executable command.", actual_cmd, interpreter );
-			}
-			else
-			{
-				debug_safe(0, "The file '%s' or a script or ELF interpreter does not exist, or a shared library needed for file or interpreter cannot be found.", actual_cmd);
-			}
-			exit_without_destructors(STATUS_EXEC_FAIL);
-		}
-
-		case ENOMEM:
-		{
-			debug_safe(0, "Out of memory");
-			exit_without_destructors(STATUS_EXEC_FAIL);
-		}
-
-		default:
-		{
-            /* Hope strerror doesn't allocate... */
-            const char *err = strerror(errno);
-            debug_safe(0, "exec: %s", err);
-			
-			//		debug(0, L"The file '%ls' is marked as an executable but could not be run by the operating system.", p->actual_cmd);
-			exit_without_destructors(STATUS_EXEC_FAIL);
-		}
-	}
+    safe_report_exec_error(errno, actual_cmd, argv, envv);
+	exit_without_destructors(STATUS_EXEC_FAIL);
 }
 
 /**
@@ -368,7 +302,7 @@ static void launch_process_nofork( process_t *p )
     ASSERT_IS_NOT_FORKED_CHILD();
     
 	char **argv = wcsv2strv(p->get_argv());
-	char **envv = env_export_arr( 0 );
+	char **envv = env_export_arr( false );
     char *actual_cmd = wcs2str(p->actual_cmd.c_str());
 	
     /* Bounce to launch_process. This never returns. */
@@ -380,102 +314,9 @@ static void launch_process_nofork( process_t *p )
    Check if the IO redirection chains contains redirections for the
    specified file descriptor
 */
-static int has_fd( io_data_t *d, int fd )
+static int has_fd( const io_chain_t &d, int fd )
 {
-	return io_get( d, fd ) != 0;
-}
-
-
-/**
-   Free a transmogrified io chain. Only the chain itself and resources
-   used by a transmogrified IO_FILE redirection are freed, since the
-   original chain may still be needed.
-*/
-static void io_untransmogrify( io_data_t * in, io_data_t *out )
-{
-	if( !out )
-		return;
-    assert(in != NULL);
-	io_untransmogrify( in->next, out->next );
-	switch( in->io_mode )
-	{
-		case IO_FILE:
-			exec_close( out->param1.old_fd );
-			break;
-	}	
-	delete out;
-}
-
-
-/**
-   Make a copy of the specified io redirection chain, but change file
-   redirection into fd redirection. This makes the redirection chain
-   suitable for use as block-level io, since the file won't be
-   repeatedly reopened for every command in the block, which would
-   reset the cursor position.
-
-   \return the transmogrified chain on sucess, or 0 on failiure
-*/
-static io_data_t *io_transmogrify( io_data_t * in )
-{
-    ASSERT_IS_MAIN_THREAD();
-	if( !in )
-		return 0;
-	
-	std::auto_ptr<io_data_t> out(new io_data_t);
-	
-	out->fd = in->fd;
-	out->io_mode = IO_FD;
-	out->param2.close_old = 1;
-	out->next=0;
-		
-	switch( in->io_mode )
-	{
-		/*
-		  These redirections don't need transmogrification. They can be passed through.
-		*/
-		case IO_FD:
-		case IO_CLOSE:
-		case IO_BUFFER:
-		case IO_PIPE:
-		{
-            out.reset(new io_data_t(*in));
-			break;
-		}
-
-		/*
-		  Transmogrify file redirections
-		*/
-		case IO_FILE:
-		{
-			int fd;
-			
-			if( (fd=open( in->filename_cstr, in->param2.flags, OPEN_MASK ) )==-1 )
-			{
-				debug( 1, 
-					   FILE_ERROR,
-					   in->filename_cstr );
-								
-				wperror( L"open" );
-				return NULL;
-			}	
-
-			out->param1.old_fd = fd;
-			break;
-		}
-	}
-	
-	if( in->next)
-	{
-		out->next = io_transmogrify( in->next );
-		if( !out->next )
-		{
-			io_untransmogrify( in, out.release() );
-			return NULL;
-		}
-	}
-	
-	return out.release();
+	return io_chain_get( d, fd ) != NULL;
 }
 
 /**
@@ -490,28 +331,17 @@ static io_data_t *io_transmogrify( io_data_t * in )
 static void internal_exec_helper( parser_t &parser,
                                   const wchar_t *def, 
 								  enum block_type_t block_type,
-								  io_data_t *io )
+								  io_chain_t &ios )
 {
-	io_data_t *io_internal = io_transmogrify( io );
 	int is_block_old=is_block;
 	is_block=1;
-	
-	/*
-	  Did the transmogrification fail - if so, set error status and return
-	*/
-	if( io && !io_internal )
-	{
-		proc_set_last_status( STATUS_EXEC_FAIL );
-		return;
-	}
-	
+
 	signal_unblock();
 	
-	parser.eval( def, io_internal, block_type );		
+	parser.eval( def, ios, block_type );
 	
 	signal_block();
 	
-	io_untransmogrify( io, io_internal );
 	job_reap( 0 );
 	is_block=is_block_old;
 }
@@ -552,7 +382,6 @@ void exec( parser_t &parser, job_t *j )
 	sigset_t chldset; 
 	
 	io_data_t pipe_read, pipe_write;
-	io_data_t *tmp;
 
 	io_data_t *io_buffer =0;
 
@@ -577,23 +406,16 @@ void exec( parser_t &parser, job_t *j )
 	
 	debug( 4, L"Exec job '%ls' with id %d", j->command_wcstr(), j->job_id );	
 	
-	if( parser.block_io )
+	if( ! parser.block_io.empty() )
 	{
-		if( j->io )
-		{
-			j->io = io_add( io_duplicate(parser.block_io), j->io );
-		}
-		else
-		{
-			j->io=io_duplicate(parser.block_io);				
-		}
+        io_duplicate_append(parser.block_io, j->io);
 	}
 
-	
-	io_data_t *input_redirect;
-
-	for( input_redirect = j->io; input_redirect; input_redirect = input_redirect->next )
+	const io_data_t *input_redirect = NULL;
+    for (size_t idx = 0; idx < j->io.size(); idx++)
 	{
+        input_redirect = j->io.at(idx);
+        
 		if( (input_redirect->io_mode == IO_BUFFER) && 
 			input_redirect->is_input )
 		{
@@ -647,11 +469,9 @@ void exec( parser_t &parser, job_t *j )
 
 	pipe_write.io_mode=IO_PIPE;
 	pipe_write.is_input = 0;
-	pipe_read.next=0;
-	pipe_write.next=0;
 	pipe_write.param1.pipe_fd[0]=pipe_write.param1.pipe_fd[1]=-1;
 	
-	j->io = io_add( j->io, &pipe_write );
+    j->io.push_back(&pipe_write);
 	
 	signal_block();
 
@@ -737,7 +557,7 @@ void exec( parser_t &parser, job_t *j )
 		   uniprocessor systems.
 		*/
 		if( p->type == EXTERNAL )
-			env_export_arr( 1 );
+			env_export_arr( true );
 		
 		
 		/*
@@ -746,7 +566,7 @@ void exec( parser_t &parser, job_t *j )
 		
 		if( p == j->first_process->next )
 		{
-			j->io = io_add( j->io, &pipe_read );
+            j->io.push_back(&pipe_read);
 		}
 		
 		if( p_wants_pipe )
@@ -769,8 +589,9 @@ void exec( parser_t &parser, job_t *j )
 			  This is the last element of the pipeline.
 			  Remove the io redirection for pipe output.
 			*/
-			j->io = io_remove( j->io, &pipe_write );
-			
+            io_chain_t::iterator where = std::find(j->io.begin(), j->io.end(), &pipe_write);
+            if (where != j->io.end())
+                j->io.erase(where);
 		}
 
 		switch( p->type )
@@ -825,8 +646,8 @@ void exec( parser_t &parser, job_t *j )
 
 				if( p->next )
 				{
-					io_buffer = io_buffer_create( 0 );					
-					j->io = io_add( j->io, io_buffer );
+					io_buffer = io_buffer_create( 0 );
+                    j->io.push_back(io_buffer);
 				}
 				
 				internal_exec_helper( parser, def, TOP, j->io );
@@ -842,8 +663,8 @@ void exec( parser_t &parser, job_t *j )
 			{
 				if( p->next )
 				{
-					io_buffer = io_buffer_create( 0 );					
-					j->io = io_add( j->io, io_buffer );
+					io_buffer = io_buffer_create( 0 );
+                    j->io.push_back(io_buffer);
 				}
                 
 				internal_exec_helper( parser, p->argv0(), TOP, j->io );			
@@ -864,7 +685,7 @@ void exec( parser_t &parser, job_t *j )
 				*/
 				if( p == j->first_process )
 				{
-					io_data_t *in = io_get( j->io, 0 );
+					const io_data_t *in = io_chain_get( j->io, 0 );
 					
 					if( in )
 					{
@@ -1040,7 +861,7 @@ void exec( parser_t &parser, job_t *j )
 					break;
 				}
 
-				j->io = io_remove( j->io, io_buffer );
+				io_remove( j->io, io_buffer );
 				
 				io_buffer_read( io_buffer );
 				
@@ -1159,7 +980,7 @@ void exec( parser_t &parser, job_t *j )
 				  performance quite a bit in complex completion code.
 				*/
 
-				io_data_t *io = io_get( j->io, 1 );
+				io_data_t *io = io_chain_get( j->io, 1 );
 				bool buffer_stdout = io && io->io_mode == IO_BUFFER;
 				
 				if( ( get_stderr_buffer().empty() ) && 
@@ -1172,10 +993,10 @@ void exec( parser_t &parser, job_t *j )
 					skip_fork = 1;
 				}
                 
-                if (! skip_fork && ! j->io) {
+                if (! skip_fork && j->io.empty()) {
                     /* PCA for some reason, fish forks a lot, even for basic builtins like echo just to write out their buffers. I'm certain a lot of this is unnecessary, but I am not sure exactly when. If j->io is NULL, then it means there's no pipes or anything, so we can certainly just write out our data. Beyond that, we may be able to do the same if io_get returns 0 for STDOUT_FILENO and STDERR_FILENO. */
                     if (g_log_forks) {
-                        printf("fork #-: Skipping fork for internal builtin for '%ls' (io is %p, job_io is %p)\n", p->argv0(), io, j->io);
+                        printf("fork #-: Skipping fork for internal builtin for '%ls'\n", p->argv0());
                     }
                     const wcstring &out = get_stdout_buffer(), &err = get_stderr_buffer();
                     char *outbuff = wcs2str(out.c_str()), *errbuff = wcs2str(err.c_str());
@@ -1185,8 +1006,9 @@ void exec( parser_t &parser, job_t *j )
                     skip_fork = 1;
                 }
 
-				for( io_data_t *tmp_io = j->io; tmp_io != NULL; tmp_io=tmp_io->next )
+                for( io_chain_t::iterator iter = j->io.begin(); iter != j->io.end(); iter++ )
 				{
+                    io_data_t *tmp_io = *iter;
 					if( tmp_io->io_mode == IO_FILE && strcmp(tmp_io->filename_cstr, "/dev/null") != 0)
 					{
 						skip_fork = 0;
@@ -1218,8 +1040,8 @@ void exec( parser_t &parser, job_t *j )
                 fflush(stdout);
                 fflush(stderr);
                 if (g_log_forks) {
-                    printf("fork #%d: Executing fork for internal builtin for '%ls' (io is %p, job_io is %p)\n", g_fork_count, p->argv0(), io, j->io);
-                    io_print(io);
+                    printf("fork #%d: Executing fork for internal builtin for '%ls'\n", g_fork_count, p->argv0());
+                    io_print(io_chain_t(io));
                 }
 				pid = execute_fork(false);
 				if( pid == 0 )
@@ -1274,33 +1096,65 @@ void exec( parser_t &parser, job_t *j )
                     const wchar_t *file = reader_current_filename();
                     const wchar_t *func = parser_t::principal_parser().is_function();
                     printf("fork #%d: forking for '%s' in '%ls:%ls'\n", g_fork_count, actual_cmd, file ? file : L"", func ? func : L"?");
+                
+                    fprintf(stderr, "IO chain for %s:\n", actual_cmd);
+                    io_print(j->io);
+                }
+                
+#if FISH_USE_POSIX_SPAWN
+                /* Prefer to use posix_spawn, since it's faster on some systems like OS X */
+                bool use_posix_spawn = g_use_posix_spawn;
+                if (use_posix_spawn)
+                {
+                    /* Create posix spawn attributes and actions */
+                    posix_spawnattr_t attr = posix_spawnattr_t();
+                    posix_spawn_file_actions_t actions = posix_spawn_file_actions_t();
+                    bool made_it = fork_actions_make_spawn_properties(&attr, &actions, j, p);
+                    if (made_it)
+                    {
+                        /* We successfully made the attributes and actions; actually call posix_spawn */
+                        int spawn_ret = posix_spawn(&pid, actual_cmd, &actions, &attr, argv, envv);
+                        if (spawn_ret != 0)
+                        {
+                            safe_report_exec_error(spawn_ret, actual_cmd, argv, envv);
+                            /* Make sure our pid isn't set */
+                            pid = 0;
+                        }
+                            
+                        /* Clean up our actions */
+                        posix_spawn_file_actions_destroy(&actions);
+                        posix_spawnattr_destroy(&attr);
+                    }
+                }
+                else
+#endif
+                {
+                    pid = execute_fork(false);
+                    if (pid == 0)
+                    {
+                        /*
+                          This is the child process. 
+                        */
+                        p->pid = getpid();
+                        setup_child_process( j, p );
+                        safe_launch_process( p, actual_cmd, argv, envv );
+                        
+                        /*
+                          safe_launch_process _never_ returns...
+                        */
+                    }
                 }
-				pid = execute_fork(false);
-				if( pid == 0 )
-				{
-					/*
-					  This is the child process. 
-					*/
-					p->pid = getpid();
-					setup_child_process( j, p );
-					safe_launch_process( p, actual_cmd, argv, envv );
-					
-					/*
-					  safe_launch_process _never_ returns...
-					*/
-				}
-				else
-				{
-					/* 
-					   This is the parent process. Store away
-					   information on the child, and possibly fice
-					   it control over the terminal.
-					*/
-					p->pid = pid;
 
-					set_child_group( j, p, 0 );
-															
-				}
+
+                /* 
+                   This is the parent process. Store away
+                   information on the child, and possibly fice
+                   it control over the terminal.
+                */
+                p->pid = pid;
+
+                set_child_group( j, p, 0 );
+
 				break;
 			}
 			
@@ -1348,10 +1202,12 @@ void exec( parser_t &parser, job_t *j )
 
 	debug( 3, L"Job is constructed" );
 
-	j->io = io_remove( j->io, &pipe_read );
-
-	for( tmp = parser.block_io; tmp; tmp=tmp->next )
-		j->io = io_remove( j->io, tmp );
+	io_remove( j->io, &pipe_read );
+    
+    for (io_chain_t::const_iterator iter = parser.block_io.begin(); iter != parser.block_io.end(); iter++)
+    {
+        io_remove( j->io, *iter );
+    }
 	
 	job_set_flag( j, JOB_CONSTRUCTED, 1 );
 
@@ -1400,7 +1256,7 @@ static int exec_subshell_internal( const wcstring &cmd, wcstring_list_t *lst )
 	prev_status = proc_get_last_status();
 	
     parser_t &parser = parser_t::principal_parser();
-	if( parser.eval( cmd, io_buffer, SUBST ) )
+	if( parser.eval( cmd, io_chain_t(io_buffer), SUBST ) )
 	{
 		status = -1;
 	}
diff --git a/exec.h b/exec.h
index 4fa4b10c6..97342f114 100644
--- a/exec.h
+++ b/exec.h
@@ -71,6 +71,12 @@ void exec_close( int fd );
 int exec_pipe( int fd[2]);
 
 /* Close all fds in open_fds. This is called from postfork.cpp */
-void close_unused_internal_pipes( io_data_t *io );
+void close_unused_internal_pipes( const io_chain_t &io );
+
+/* Gets all unused internal pipes into fds */
+void get_unused_internal_pipes(std::vector<int> &fds, const io_chain_t &io);
+
+/** Gets the interpreter for a given command */
+char *get_interpreter( const char *command, char *interpreter, size_t buff_size );
 
 #endif
diff --git a/fish.cpp b/fish.cpp
index 5e8c6b62d..baf8a7741 100644
--- a/fish.cpp
+++ b/fish.cpp
@@ -216,8 +216,10 @@ static struct config_paths_t determine_config_directory_paths(const char *argv0)
 static int read_init(const struct config_paths_t &paths)
 {
     parser_t &parser = parser_t::principal_parser();
-	parser.eval( L"builtin . " + paths.data + L"/config.fish 2>/dev/null", 0, TOP );
-	parser.eval( L"builtin . " + paths.sysconf + L"/config.fish 2>/dev/null", 0, TOP );
+    const io_chain_t empty_ios;
+	parser.eval( L"builtin . " + paths.data + L"/config.fish 2>/dev/null", empty_ios, TOP );
+	parser.eval( L"builtin . " + paths.sysconf + L"/config.fish 2>/dev/null", empty_ios, TOP );
+
 	
 	/*
 	  We need to get the configuration directory before we can source the user configuration file
@@ -232,7 +234,7 @@ static int read_init(const struct config_paths_t &paths)
 	{
 		wcstring config_dir_escaped = escape_string( config_dir, 1 );
         wcstring eval_buff = format_string(L"builtin . %ls/config.fish 2>/dev/null", config_dir_escaped.c_str());
-		parser.eval( eval_buff, 0, TOP );
+		parser.eval( eval_buff, empty_ios, TOP );
 	}
 	
 	return 1;
@@ -453,12 +455,13 @@ int main( int argc, char **argv )
     if (g_log_forks)
         printf("%d: g_fork_count: %d\n", __LINE__, g_fork_count);
 
+    const io_chain_t empty_ios;
 	if( read_init(paths) )
 	{
 		if( cmd != 0 )
 		{
 			wchar_t *cmd_wcs = str2wcs( cmd );
-			res = parser.eval( cmd_wcs, 0, TOP );
+			res = parser.eval( cmd_wcs, empty_ios, TOP );
 			free(cmd_wcs);
 			reader_exit(0, 0);
 		}
@@ -466,7 +469,7 @@ int main( int argc, char **argv )
 		{
 			if( my_optind == argc )
 			{
-				res = reader_read( STDIN_FILENO, 0 );
+				res = reader_read( STDIN_FILENO, empty_ios );
 			}
 			else
 			{
@@ -511,7 +514,7 @@ int main( int argc, char **argv )
 				free( rel_filename );
 				free( abs_filename );
 
-				res = reader_read( fd, 0 );
+				res = reader_read( fd, empty_ios );
 
 				if( res )
 				{
diff --git a/fish_tests.cpp b/fish_tests.cpp
index e682acdb7..a5bddfa23 100644
--- a/fish_tests.cpp
+++ b/fish_tests.cpp
@@ -451,7 +451,7 @@ static void test_parser()
 		err( L"Null input when evaluating undetected" );
 	}
 #endif
-	if( !parser.eval( L"ls", 0, WHILE ) )
+	if( !parser.eval( L"ls", io_chain_t(), WHILE ) )
 	{
 		err( L"Invalid block mode when evaluating undetected" );
 	}	
diff --git a/input.cpp b/input.cpp
index 0ae04c547..38164d21e 100644
--- a/input.cpp
+++ b/input.cpp
@@ -411,7 +411,7 @@ static wint_t input_exec_binding( const input_mapping_t &m, const wcstring &seq
 		*/
 		int last_status = proc_get_last_status();
 	  		
-		parser_t::principal_parser().eval( m.command.c_str(), 0, TOP );
+		parser_t::principal_parser().eval( m.command.c_str(), io_chain_t(), TOP );
 		
 		proc_set_last_status( last_status );
 		
diff --git a/io.cpp b/io.cpp
index 10648c5bc..176fb2a34 100644
--- a/io.cpp
+++ b/io.cpp
@@ -12,6 +12,8 @@ Utilities for io redirection.
 #include <string.h>
 #include <errno.h>
 #include <sys/types.h>
+#include <set>
+#include <algorithm>
 
 #ifdef HAVE_SYS_TERMIOS_H
 #include <sys/termios.h>
@@ -98,20 +100,20 @@ void io_buffer_read( io_data_t *d )
 }
 
 
-io_data_t *io_buffer_create( int is_input )
+io_data_t *io_buffer_create( bool is_input )
 {
-	std::auto_ptr<io_data_t> buffer_redirect(new io_data_t);
+    bool success = true;
+	io_data_t *buffer_redirect = new io_data_t;
 	buffer_redirect->out_buffer_create();
-	buffer_redirect->io_mode=IO_BUFFER;
-	buffer_redirect->next=0;
-	buffer_redirect->is_input = is_input;
+	buffer_redirect->io_mode = IO_BUFFER;
+	buffer_redirect->is_input = is_input ? true : false;
 	buffer_redirect->fd=is_input?0:1;
 	
 	if( exec_pipe( buffer_redirect->param1.pipe_fd ) == -1 )
 	{
 		debug( 1, PIPE_ERROR );
 		wperror (L"pipe");
-		return NULL;
+		success = false;
 	}
 	else if( fcntl( buffer_redirect->param1.pipe_fd[0],
 					F_SETFL,
@@ -119,9 +121,16 @@ io_data_t *io_buffer_create( int is_input )
 	{
 		debug( 1, PIPE_ERROR );
 		wperror( L"fcntl" );
-		return NULL;
+		success = false;
 	}
-	return buffer_redirect.release();
+    
+    if (! success)
+    {
+        delete buffer_redirect;
+        buffer_redirect = NULL;
+    }
+    
+	return buffer_redirect;
 }
 
 void io_buffer_destroy( io_data_t *io_buffer )
@@ -145,98 +154,146 @@ void io_buffer_destroy( io_data_t *io_buffer )
 	delete io_buffer;
 }
 
-
-
-io_data_t *io_add( io_data_t *list, io_data_t *element )
+void io_chain_t::remove(const io_data_t *element)
 {
-	io_data_t *curr = list;
-	if( curr == 0 )
-		return element;
-	while( curr->next != 0 )
-		curr = curr->next;
-	curr->next = element;
-	return list;
+    // See if you can guess why std::find doesn't work here
+    for (io_chain_t::iterator iter = this->begin(); iter != this->end(); ++iter)
+    {
+        if (*iter == element)
+        {
+            this->erase(iter);
+            break;
+        }
+    }
 }
 
-io_data_t *io_remove( io_data_t *list, io_data_t *element )
+io_chain_t io_chain_t::duplicate() const
 {
-	io_data_t *curr, *prev=0;
-	for( curr=list; curr; curr = curr->next )
-	{		
-		if( element == curr )
-		{
-			if( prev == 0 )
-			{
-				io_data_t *tmp = element->next;
-				element->next = 0;
-				return tmp;
-			}
-			else
-			{
-				prev->next = element->next;
-				element->next = 0;
-				return list;
-			}
-		}
-		prev = curr;
-	}
-	return list;
+    io_chain_t result;
+    result.reserve(this->size());
+    for (io_chain_t::const_iterator iter = this->begin(); iter != this->end(); iter++)
+    {
+        const io_data_t *io = *iter;
+        result.push_back(new io_data_t(*io));
+    }
+    return result;
 }
 
-io_data_t *io_duplicate( io_data_t *l )
+void io_chain_t::duplicate_append(const io_chain_t &src)
 {
-	io_data_t *res;
-	
-	if( l == 0 )
-		return 0;
-
-	res = new io_data_t(*l);
-	res->next=io_duplicate(l->next );
-	return res;	
+    this->reserve(this->size() + src.size());
+    for (size_t idx = 0; idx < src.size(); idx++)
+    {
+        const io_data_t *src_data = src.at(idx);
+        this->push_back(new io_data_t(*src_data));
+    }
 }
 
-io_data_t *io_get( io_data_t *io, int fd )
+void io_chain_t::destroy()
 {
-	if( io == NULL )
-		return 0;
-	
-	io_data_t *res = io_get( io->next, fd );
-	if( res )
-		return res;
-	
-	if( io->fd == fd )
-		return io;
-
-	return 0;
+    for (size_t idx = 0; idx < this->size(); idx++)
+    {
+        delete this->at(idx);
+    }
+    this->clear();
 }
 
-
-void io_print( io_data_t *io )
+void io_remove(io_chain_t &list, const io_data_t *element)
+{
+    list.remove(element);
+}
+
+io_chain_t io_duplicate(const io_chain_t &chain)
+{
+    return chain.duplicate();
+}
+
+void io_print(const io_chain_t &chain)
+{
+    if (chain.empty())
+    {
+        fprintf(stderr, "Empty chain %p\n", &chain);
+        return;
+    }
+    
+    fprintf(stderr, "Chain %p (%ld items):\n", &chain, (long)chain.size());
+    for (size_t i=0; i < chain.size(); i++) {
+        const io_data_t *io = chain.at(i);
+        fprintf(stderr, "\t%lu: fd:%d, input:%s, ", (unsigned long)i, io->fd, io->is_input ? "yes" : "no");
+        switch (io->io_mode)
+        {
+            case IO_FILE:
+                fprintf(stderr, "file (%s)\n", io->filename_cstr);
+                break;
+            case IO_PIPE:
+                fprintf(stderr, "pipe {%d, %d}\n", io->param1.pipe_fd[0], io->param1.pipe_fd[1]);
+                break;
+            case IO_FD:
+                fprintf(stderr, "FD map %d -> %d\n", io->param1.old_fd, io->fd);
+                break;
+            case IO_BUFFER:
+                fprintf(stderr, "buffer %p (size %lu)\n", io->out_buffer_ptr(), io->out_buffer_size());
+                break;
+            case IO_CLOSE:
+                fprintf(stderr, "close %d\n", io->fd);
+                break;
+        }
+    }
+}
+
+void io_duplicate_append( const io_chain_t &src, io_chain_t &dst )
+{
+    return dst.duplicate_append(src);
+}
+
+void io_chain_destroy(io_chain_t &chain) 
+{
+    chain.destroy();
+}
+
+/* Return the last IO for the given fd */
+const io_data_t *io_chain_t::get_io_for_fd(int fd) const
+{
+    size_t idx = this->size();
+    while (idx--)
+    {
+        const io_data_t *data = this->at(idx);
+        if (data->fd == fd) {
+            return data;
+        }
+    }
+    return NULL;
+}
+
+io_data_t *io_chain_t::get_io_for_fd(int fd)
+{
+    size_t idx = this->size();
+    while (idx--)
+    {
+        io_data_t *data = this->at(idx);
+        if (data->fd == fd) {
+            return data;
+        }
+    }
+    return NULL;
+}
+
+/* The old function returned the last match, so we mimic that. */
+const io_data_t *io_chain_get(const io_chain_t &src, int fd)
+{
+    return src.get_io_for_fd(fd);
+}
+
+io_data_t *io_chain_get(io_chain_t &src, int fd)
+{
+    return src.get_io_for_fd(fd);
+}
+
+io_chain_t::io_chain_t(io_data_t *data) : std::vector<io_data_t *>(1, data)
+{
+
+}
+
+io_chain_t::io_chain_t() : std::vector<io_data_t *>()
 {
-	if( !io )
-	{
-		return;
-	}
-	
-	debug( 1, L"IO fd %d, type ", io->fd );
-	switch( io->io_mode )
-	{
-		case IO_PIPE:
-			debug( 1, L"PIPE, data %d", io->param1.pipe_fd[io->fd?1:0] );
-			break;
-		
-		case IO_FD:
-			debug( 1, L"FD, copy %d", io->param1.old_fd );
-			break;
-
-		case IO_BUFFER:
-			debug( 1, L"BUFFER" );
-			break;
-			
-		default:
-			debug( 1, L"OTHER" );
-	}
-
-	io_print( io->next );
-	
 }
diff --git a/io.h b/io.h
index 49bbbafa8..109c1a5ab 100644
--- a/io.h
+++ b/io.h
@@ -73,7 +73,12 @@ public:
     /** Function to get a pointer to the buffer */
     char *out_buffer_ptr(void) {
         assert(out_buffer.get() != NULL);
-        return (out_buffer->size() == 0) ? NULL : &out_buffer->at(0);
+        return out_buffer->empty() ? NULL : &out_buffer->at(0);
+    }
+    
+    const char *out_buffer_ptr(void) const {
+        assert(out_buffer.get() != NULL);
+        return out_buffer->empty() ? NULL : &out_buffer->at(0);
     }
     
     /** Function to get the size of the buffer */
@@ -83,11 +88,8 @@ public:
     }
 
 	/** Set to true if this is an input io redirection */
-	int is_input;
+	bool is_input;
 	
-	/** Pointer to the next IO redirection */
-	io_data_t *next;
-    
     io_data_t() :
         out_buffer(),
         io_mode(0),
@@ -95,8 +97,7 @@ public:
         param1(),
         param2(),
         filename_cstr(NULL),
-        is_input(0),
-        next(NULL)
+        is_input(0)
     {
     }
     
@@ -107,10 +108,8 @@ public:
         param1(rhs.param1),
         param2(rhs.param2),
         filename_cstr(rhs.filename_cstr ? strdup(rhs.filename_cstr) : NULL),
-        is_input(rhs.is_input),
-        next(rhs.next)
+        is_input(rhs.is_input)
     {
-        
     }
     
     ~io_data_t() {
@@ -118,27 +117,44 @@ public:
     }
 };
 
- 
-/**
-   Join two chains of io redirections
-*/
-io_data_t *io_add( io_data_t *first_chain, io_data_t *decond_chain );
+class io_chain_t : public std::vector<io_data_t *> {
+public:
+    io_chain_t();
+    io_chain_t(io_data_t *);
+    
+    void remove(const io_data_t *element);
+    io_chain_t duplicate() const;
+    void duplicate_append(const io_chain_t &src);
+    void destroy();
+    
+    const io_data_t *get_io_for_fd(int fd) const;
+    io_data_t *get_io_for_fd(int fd);
+    
+    
+};
 
 /**
    Remove the specified io redirection from the chain
 */
-io_data_t *io_remove( io_data_t *list, io_data_t *element );
+void io_remove(io_chain_t &list, const io_data_t *element);
 
-/**
-   Make a copy of the specified chain of redirections. Uses operator new.
-*/
-io_data_t *io_duplicate( io_data_t *l );
+/** Make a copy of the specified chain of redirections. Uses operator new. */
+io_chain_t io_duplicate(const io_chain_t &chain);
+
+/** Return a shallow copy of the specified chain of redirections that contains only the applicable redirections. That is, if there's multiple redirections for the same fd, only the second one is included. */
+io_chain_t io_unique(const io_chain_t &chain);
+
+/** Appends a copy of the specified 'src' chain of redirections to 'dst.' Uses operator new. */
+void io_duplicate_append( const io_chain_t &src, io_chain_t &dst );
+
+/** Destroys an io_chain */
+void io_chain_destroy(io_chain_t &chain);
 
 /**
    Return the last io redirection in the chain for the specified file descriptor.
 */
-io_data_t *io_get( io_data_t *io, int fd );
-
+const io_data_t *io_chain_get(const io_chain_t &src, int fd);
+io_data_t *io_chain_get(io_chain_t &src, int fd);
 
 
 /**
@@ -155,16 +171,14 @@ void io_buffer_destroy( io_data_t *io_buffer );
    used to buffer the output of a command, or non-zero to buffer the
    input to a command.
 */
-io_data_t *io_buffer_create( int is_input );
+io_data_t *io_buffer_create( bool is_input );
 
 /**
    Close output pipe, and read from input pipe until eof.
 */
 void io_buffer_read( io_data_t *d );
 
-/**
-   Print debug information about the specified IO redirection chain to stderr.
-*/
-void io_print( io_data_t *io );
+/** Print debug information about the specified IO redirection chain to stderr. */
+void io_print( const io_chain_t &chain );
 
 #endif
diff --git a/osx/config.h b/osx/config.h
index f606d92fe..a72a8825d 100644
--- a/osx/config.h
+++ b/osx/config.h
@@ -1,9 +1,6 @@
 /* config.h.  Generated from config.h.in by configure.  */
 /* config.h.in.  Generated from configure.ac by autoheader.  */
 
-#ifndef FISH_CONFIG_H
-#define FISH_CONFIG_H
-
 /* Define to 1 if you have the `backtrace' function. */
 #define HAVE_BACKTRACE 1
 
@@ -76,6 +73,9 @@
 /* Define to 1 if you have the <siginfo.h> header file. */
 /* #undef HAVE_SIGINFO_H */
 
+/* Define to 1 if you have the <spawn.h> header file. */
+#define HAVE_SPAWN_H 1
+
 /* Define to 1 if you have the <stdint.h> header file. */
 #define HAVE_STDINT_H 1
 
@@ -219,5 +219,3 @@
 #define __warn_unused
 #define __sentinel
 #endif
-
-#endif
diff --git a/parser.cpp b/parser.cpp
index 3e95ee8e9..d701d56ad 100644
--- a/parser.cpp
+++ b/parser.cpp
@@ -1541,7 +1541,7 @@ void parser_t::parse_job_argument_list( process_t *p,
 								   tok_get_desc( tok_last_type(tok)) );
 					}
 
-					if( ! has_target || target.size() == 0 )
+					if( ! has_target || target.empty() )
 					{
 						if( error_code == 0 )
 							error( SYNTAX_ERROR,
@@ -1611,7 +1611,7 @@ void parser_t::parse_job_argument_list( process_t *p,
 					}
 				}
 
-				j->io = io_add( j->io, new_io.release() );
+				j->io.push_back(new_io.release());
 				
 			}
 			break;
@@ -2488,14 +2488,18 @@ void parser_t::eval_job( tokenizer *tok )
 
 }
 
-int parser_t::eval( const wcstring &cmdStr, io_data_t *io, enum block_type_t block_type )
+int parser_t::eval( const wcstring &cmdStr, const io_chain_t &io, enum block_type_t block_type )
 {
     const wchar_t * const cmd = cmdStr.c_str();
 	size_t forbid_count;
 	int code;
 	tokenizer *previous_tokenizer=current_tokenizer;
 	block_t *start_current_block = current_block;
-	io_data_t *prev_io = block_io;
+    
+    /* Record the current chain so we can put it back later */
+    const io_chain_t prev_io = block_io;
+    block_io = io;
+    
     std::vector<wcstring> prev_forbidden = forbidden_function;
 
 	if( block_type == SUBST )
diff --git a/parser.h b/parser.h
index b74a239ca..272008335 100644
--- a/parser.h
+++ b/parser.h
@@ -347,7 +347,7 @@ class parser_t {
     event_block_list_t global_event_blocks;
     
     /** Current block level io redirections  */
-    io_data_t *block_io;
+    io_chain_t block_io;
     
     /**
       Evaluate the expressions contained in cmd.
@@ -358,7 +358,7 @@ class parser_t {
 
       \return 0 on success, 1 otherwise
     */
-    int eval( const wcstring &cmd, io_data_t *io, enum block_type_t block_type );
+    int eval( const wcstring &cmdStr, const io_chain_t &io, enum block_type_t block_type );
     
     /**
       Evaluate line as a list of parameters, i.e. tokenize it and perform parameter expansion and cmdsubst execution on the tokens.
diff --git a/postfork.cpp b/postfork.cpp
index 7b210ff48..07842cb09 100644
--- a/postfork.cpp
+++ b/postfork.cpp
@@ -9,7 +9,6 @@
 #include "iothread.h"
 #include "exec.h"
 
-
 /** The number of times to try to call fork() before giving up */
 #define FORK_LAPS 5
 
@@ -102,39 +101,49 @@ int set_child_group( job_t *j, process_t *p, int print_errors )
 	return res;
 }
 
-/** Make sure the fd used by this redirection is not used by i.e. a pipe.  */
-static void free_fd( io_data_t *io, int fd )
+/** Make sure the fd used by each redirection is not used by a pipe.  */
+static void free_redirected_fds_from_pipes(io_chain_t &io_chain)
 {
-	if( !io )
-		return;
-	
-	if( ( io->io_mode == IO_PIPE ) || ( io->io_mode == IO_BUFFER ) )
-	{
-		int i;
-		for( i=0; i<2; i++ )
-		{
-			if(io->param1.pipe_fd[i] == fd )
-			{
-				while(1)
-				{
-					if( (io->param1.pipe_fd[i] = dup(fd)) == -1)
-					{
-						 if( errno != EINTR )
-						{
-							debug_safe_int( 1, FD_ERROR, fd );							
-							wperror( L"dup" );
-							FATAL_EXIT();
-						}
-					}
-					else
-					{
-						break;
-					}
-				}
-			}
-		}
+    size_t max = io_chain.size();
+    for (size_t i = 0; i < max; i++)
+    {
+        int fd_to_free = io_chain.at(i)->fd;
+        
+        /* We only have to worry about fds beyond the three standard ones */
+        if (fd_to_free <= 2)
+            continue;
+
+        /* Make sure the fd is not used by a pipe */
+        for (size_t j = 0; j < max; j++)
+        {
+            /* We're only interested in pipes */
+            io_data_t *possible_conflict = io_chain.at(j);
+            if (possible_conflict->io_mode != IO_PIPE && possible_conflict->io_mode != IO_BUFFER)
+                continue;
+            
+            /* If the pipe is a conflict, dup it to some other value */
+            for (int k=0; k<2; k++)
+            {
+                /* If it's not a conflict, we don't care */
+                if (possible_conflict->param1.pipe_fd[k] != fd_to_free)
+                    continue;
+                
+                /* Repeat until we have a replacement fd */
+                int replacement_fd = -1;
+                while (replacement_fd < 0)
+                {
+                    replacement_fd = dup(fd_to_free);
+                    if (replacement_fd == -1 && errno != EINTR)
+                    {
+                        debug_safe_int( 1, FD_ERROR, fd_to_free );
+                        wperror( L"dup" );
+                        FATAL_EXIT();
+                    }
+                }
+                possible_conflict->param1.pipe_fd[k] = replacement_fd;
+            }
+        }
 	}
-	free_fd( io->next, fd );
 }
 
 
@@ -150,25 +159,24 @@ static void free_fd( io_data_t *io, int fd )
 
    \return 0 on sucess, -1 on failiure
 */
-static int handle_child_io( io_data_t *io )
+static int handle_child_io( io_chain_t &io_chain )
 {
 
-	close_unused_internal_pipes( io );
-
-	for( ; io; io=io->next )
+	close_unused_internal_pipes( io_chain );
+    free_redirected_fds_from_pipes(io_chain);
+	for (size_t idx = 0; idx < io_chain.size(); idx++)
 	{
+        io_data_t *io = io_chain.at(idx);
 		int tmp;
+        
+        /* If this is not the last IO redirection for this fd, then skip it. This comes about because of the funky way in which we list IO redirections: every process in a job gets the input and output redirections, even internal ones. For example, in 'cat < foo | cat | cat > bar', the middle cat sees both < foo and > bar. It also gets pipes for its fd 0 and 1, which appear after in the list. */
+        if (io != io_chain.get_io_for_fd(io->fd))
+            continue;
 
 		if( io->io_mode == IO_FD && io->fd == io->param1.old_fd )
 		{
 			continue;
 		}
-
-		if( io->fd > 2 )
-		{
-			/* Make sure the fd used by this redirection is not used by e.g. a pipe.  */
-			free_fd( io, io->fd );
-		}
 				
 		switch( io->io_mode )
 		{
@@ -184,7 +192,7 @@ static int handle_child_io( io_data_t *io )
 
 			case IO_FILE:
 			{
-                // Here we definitely do not want to set CLO_EXEC because our child needs access
+				// Here we definitely do not want to set CLO_EXEC because our child needs access
 				if( (tmp=open( io->filename_cstr,
 						io->param2.flags, OPEN_MASK ) )==-1 )
 				{
@@ -240,6 +248,7 @@ static int handle_child_io( io_data_t *io )
 			case IO_BUFFER:
 			case IO_PIPE:
 			{
+                /* If write_pipe_idx is 0, it means we're connecting to the read end (first pipe fd). If it's 1, we're connecting to the write end (second pipe fd). */
 				unsigned int write_pipe_idx = (io->is_input ? 0 : 1);
 /*
 				debug( 0,
@@ -256,16 +265,11 @@ static int handle_child_io( io_data_t *io )
 					perror( "dup2" );
 					return -1;
 				}
-
-				if( write_pipe_idx > 0 ) 
-				{
-					exec_close( io->param1.pipe_fd[0]);
-					exec_close( io->param1.pipe_fd[1]);
-				}
-				else
-				{
-					exec_close( io->param1.pipe_fd[0] );
-				}
+                
+                if (io->param1.pipe_fd[0] >= 0)
+                    exec_close( io->param1.pipe_fd[0]);
+                if (io->param1.pipe_fd[1] >= 0)
+                    exec_close( io->param1.pipe_fd[1]);
 				break;
 			}
 			
@@ -304,8 +308,7 @@ int setup_child_process( job_t *j, process_t *p )
 	/* Remove all signal blocks */
 	signal_unblock();	
 	
-	return ok ? 0 : -1;
-	
+	return ok ? 0 : -1;	
 }
 
 int g_fork_count = 0;
@@ -362,3 +365,239 @@ pid_t execute_fork(bool wait_for_threads_to_die)
 	FATAL_EXIT();
     return 0;
 }
+
+#if FISH_USE_POSIX_SPAWN
+bool fork_actions_make_spawn_properties(posix_spawnattr_t *attr, posix_spawn_file_actions_t *actions, job_t *j, process_t *p)
+{
+    /* Initialize the output */
+    if (posix_spawnattr_init(attr) != 0) {
+        return false;
+    }
+    
+    if (posix_spawn_file_actions_init(actions) != 0) {
+        posix_spawnattr_destroy(attr);
+        return false;
+    }
+        
+    bool should_set_parent_group_id = false;
+    int desired_parent_group_id = 0;
+    if (job_get_flag(j, JOB_CONTROL))
+    {
+        should_set_parent_group_id = true;
+        
+        // PCA: I'm quite fuzzy on process groups,
+        // but I believe that the default value of 0
+        // means that the process becomes its own
+        // group leader, which is what set_child_group did
+        // in this case. So we want this to be 0 if j->pgid is 0.
+        desired_parent_group_id = j->pgid;
+    }
+    
+	/* Set the handling for job control signals back to the default.  */
+	bool reset_signal_handlers = true;
+    
+	/* Remove all signal blocks */
+	bool reset_sigmask = true;
+    
+    /* Set our flags */
+    short flags = 0;
+    if (reset_signal_handlers)
+        flags |= POSIX_SPAWN_SETSIGDEF;
+    if (reset_sigmask)
+        flags |= POSIX_SPAWN_SETSIGMASK;
+    if (should_set_parent_group_id)
+        flags |= POSIX_SPAWN_SETPGROUP;
+    
+    int err = 0;
+    if (! err)
+        err = posix_spawnattr_setflags(attr, flags);
+
+    /* Everybody gets default handlers */
+    if (! err && reset_signal_handlers)
+    {
+        sigset_t sigdefault;
+        get_signals_with_handlers(&sigdefault);
+        err = posix_spawnattr_setsigdefault(attr, &sigdefault);
+    }
+    
+    /* No signals blocked */
+    sigset_t sigmask;
+    sigemptyset(&sigmask);
+    if (! err && reset_sigmask)
+        err = posix_spawnattr_setsigmask(attr, &sigmask);
+        
+    /* Make sure that our pipes don't use an fd that the redirection itself wants to use */
+    free_redirected_fds_from_pipes(j->io);
+    
+    /* Close unused internal pipes */
+    std::vector<int> files_to_close;
+    get_unused_internal_pipes(files_to_close, j->io);
+    for (size_t i = 0; ! err && i < files_to_close.size(); i++)
+    {
+        err = posix_spawn_file_actions_addclose(actions, files_to_close.at(i));
+    }
+    
+    for (size_t idx = 0; idx < j->io.size(); idx++)
+    {
+        const io_data_t *io = j->io.at(idx);
+        
+        /* If this is not the last IO redirection for this fd, then skip it. This comes about because of the funky way in which we list IO redirections: every process in a job gets the input and output redirections, even internal ones. For example, in 'cat < foo | cat | cat > bar', the middle cat sees both < foo and > bar. It also gets pipes for its fd 0 and 1, which appear after in the list. */
+        if (io != j->io.get_io_for_fd(io->fd))
+            continue;
+
+		if( io->io_mode == IO_FD && io->fd == io->param1.old_fd )
+		{
+			continue;
+		}
+        
+		if( io->fd > 2 )
+		{
+			/* Make sure the fd used by this redirection is not used by e.g. a pipe. */
+            // free_fd(io_chain, io->fd );
+            // PCA I don't think we need to worry about this. fd redirection is pretty uncommon anyways.
+		}
+        switch (io->io_mode)
+        {
+            case IO_CLOSE:
+            {
+                if (! err)
+                    err = posix_spawn_file_actions_addclose(actions, io->fd);
+                break;
+            }
+            
+            case IO_FILE:
+            {
+                if (! err) 
+                    err = posix_spawn_file_actions_addopen(actions, io->fd, io->filename_cstr, io->param2.flags /* mode */, OPEN_MASK);
+                break;
+            }
+            
+            case IO_FD:
+            {
+                if (! err)
+                    err = posix_spawn_file_actions_adddup2(actions, io->param1.old_fd /* from */, io->fd /* to */);
+                break;
+            }
+            
+			case IO_BUFFER:
+			case IO_PIPE:
+			{
+                unsigned int write_pipe_idx = (io->is_input ? 0 : 1);
+                int from_fd = io->param1.pipe_fd[write_pipe_idx];
+                int to_fd = io->fd;
+                if (! err)
+                    err = posix_spawn_file_actions_adddup2(actions, from_fd, to_fd);
+
+                
+				if( write_pipe_idx > 0 ) 
+				{
+                    if (! err) 
+                        err = posix_spawn_file_actions_addclose(actions, io->param1.pipe_fd[0]);
+                    if (! err)
+                        err = posix_spawn_file_actions_addclose(actions, io->param1.pipe_fd[1]);
+				}
+				else
+				{
+                    if (! err) 
+                        err = posix_spawn_file_actions_addclose(actions, io->param1.pipe_fd[0]);
+
+				}
+                break;
+            }
+        }
+    }
+    
+    /* Clean up on error */
+    if (err) {
+        posix_spawnattr_destroy(attr);
+        posix_spawn_file_actions_destroy(actions);
+    }
+    
+    return ! err;
+}
+#endif //FISH_USE_POSIX_SPAWN
+
+void safe_report_exec_error(int err, const char *actual_cmd, char **argv, char **envv)
+{
+	debug_safe( 0, "Failed to execute process '%s'. Reason:", actual_cmd );
+	
+	switch( err )
+	{
+		
+		case E2BIG:
+		{
+			char sz1[128], sz2[128];
+			
+			long arg_max = -1;
+
+			size_t sz = 0;
+			char **p;
+			for(p=argv; *p; p++)
+			{
+				sz += strlen(*p)+1;
+			}
+			
+			for(p=envv; *p; p++)
+			{
+				sz += strlen(*p)+1;
+			}
+			
+            format_size_safe(sz1, sz);
+			arg_max = sysconf( _SC_ARG_MAX );
+			
+			if( arg_max > 0 )
+			{
+                format_size_safe(sz2, sz);
+                debug_safe(0, "The total size of the argument and environment lists %s exceeds the operating system limit of %s.", sz1, sz2);
+			}
+			else
+			{
+				debug_safe( 0, "The total size of the argument and environment lists (%s) exceeds the operating system limit.", sz1);
+			}
+			
+			debug_safe(0, "Try running the command again with fewer arguments.");
+			break;
+		}
+
+		case ENOEXEC:
+		{
+            /* Hope strerror doesn't allocate... */
+            const char *err = strerror(errno);
+            debug_safe(0, "exec: %s", err);
+			
+			debug_safe(0, "The file '%s' is marked as an executable but could not be run by the operating system.", actual_cmd);
+            break;
+		}
+
+		case ENOENT:
+		{
+            char interpreter_buff[128] = {}, *interpreter;
+            interpreter = get_interpreter(actual_cmd, interpreter_buff, sizeof interpreter_buff);
+			if( interpreter && 0 != access( interpreter, X_OK ) )
+			{
+				debug_safe(0, "The file '%s' specified the interpreter '%s', which is not an executable command.", actual_cmd, interpreter );
+			}
+			else
+			{
+				debug_safe(0, "The file '%s' or a script or ELF interpreter does not exist, or a shared library needed for file or interpreter cannot be found.", actual_cmd);
+			}
+            break;
+		}
+
+		case ENOMEM:
+		{
+			debug_safe(0, "Out of memory");
+            break;
+		}
+
+		default:
+		{
+            /* Hope strerror doesn't allocate... */
+            const char *err = strerror(errno);
+            debug_safe(0, "exec: %s", err);
+			
+			//		debug(0, L"The file '%ls' is marked as an executable but could not be run by the operating system.", p->actual_cmd);
+            break;
+		}
+	}
+}
diff --git a/postfork.h b/postfork.h
index 741e6369c..9acd4c86c 100644
--- a/postfork.h
+++ b/postfork.h
@@ -19,6 +19,15 @@
 #include "wutil.h"
 #include "io.h"
 
+#if HAVE_SPAWN_H
+#include <spawn.h>
+#endif
+
+#ifndef FISH_USE_POSIX_SPAWN
+ #define FISH_USE_POSIX_SPAWN HAVE_SPAWN_H
+#endif
+
+
 /**
    This function should be called by both the parent process and the
    child right after fork() has been called. If job control is
@@ -44,6 +53,7 @@ int set_child_group( job_t *j, process_t *p, int print_errors );
 
    \param j the job to set up the IO for
    \param p the child process to set up
+   \param io_chain the IO chain to use (ignores the job's iochain)
 
    \return 0 on sucess, -1 on failiure. When this function returns,
    signals are always unblocked. On failiure, signal handlers, io
@@ -55,4 +65,12 @@ int setup_child_process( job_t *j, process_t *p );
 */
 pid_t execute_fork(bool wait_for_threads_to_die);
 
+/** Report an error from failing to exec or posix_spawn a command */
+void safe_report_exec_error(int err, const char *actual_cmd, char **argv, char **envv);
+
+#if FISH_USE_POSIX_SPAWN
+/* Initializes and fills in a posix_spawnattr_t; on success, the caller should destroy it via posix_spawnattr_destroy */
+bool fork_actions_make_spawn_properties(posix_spawnattr_t *attr, posix_spawn_file_actions_t *actions, job_t *j, process_t *p);
+#endif
+
 #endif
diff --git a/proc.cpp b/proc.cpp
index 7de06af53..fe4b9dda9 100644
--- a/proc.cpp
+++ b/proc.cpp
@@ -491,6 +491,51 @@ static void handle_child_status( pid_t pid, int status )
 	return;
 }
 
+process_t::process_t() :
+    argv_array(),
+    argv0_narrow(),
+    type(0),
+    actual_cmd(),
+    pid(0),
+    pipe_write_fd(0),
+    pipe_read_fd(0),
+    completed(0),
+    stopped(0),
+    status(0),
+    count_help_magic(0),
+    next(NULL)
+#ifdef HAVE__PROC_SELF_STAT
+    ,last_time(),
+    last_jiffies(0)
+#endif
+{
+}
+    
+process_t::~process_t()
+{
+    if (this->next != NULL)
+        delete this->next;
+}
+
+job_t::job_t(job_id_t jobid) :
+        command_str(),
+        command_narrow(),
+        first_process(NULL),
+        pgid(0),
+        tmodes(),
+        job_id(jobid),
+        io(),
+        flags(0)
+{
+}
+    
+job_t::~job_t()
+{
+    if (first_process != NULL)
+        delete first_process;
+    io_chain_destroy(this->io);
+    release_job_id(job_id);
+}
 
 /* This is called from a signal handler */
 void job_handle_signal ( int signal, siginfo_t *info, void *con )
@@ -808,12 +853,12 @@ static int select_try( job_t *j )
 {
 	fd_set fds;
 	int maxfd=-1;
-	io_data_t *d;
 
 	FD_ZERO(&fds);
 	
-	for( d = j->io; d; d=d->next )
+    for (size_t idx = 0; idx < j->io.size(); idx++)
 	{
+        const io_data_t *d = j->io.at(idx);
 		if( d->io_mode == IO_BUFFER )
 		{
 			int fd = d->param1.pipe_fd[0];
@@ -846,14 +891,14 @@ static int select_try( job_t *j )
 */
 static void read_try( job_t *j )
 {
-	io_data_t *d, *buff=0;
+	io_data_t *buff=NULL;
 
 	/*
 	  Find the last buffer, which is the one we want to read from
 	*/
-	for( d = j->io; d; d=d->next )
+    for (size_t idx = 0; idx < j->io.size(); idx++)
 	{
-		
+        io_data_t *d = j->io.at(idx);
 		if( d->io_mode == IO_BUFFER )
 		{
 			buff=d;
diff --git a/proc.h b/proc.h
index b313dac59..30c1defb2 100644
--- a/proc.h
+++ b/proc.h
@@ -140,31 +140,9 @@ class process_t
     
     public:
     
-    process_t() :
-        argv_array(),
-        argv0_narrow(),
-        type(0),
-        actual_cmd(),
-        pid(0),
-        pipe_write_fd(0),
-        pipe_read_fd(0),
-        completed(0),
-        stopped(0),
-        status(0),
-        count_help_magic(0),
-        next(NULL)
-#ifdef HAVE__PROC_SELF_STAT
-        ,last_time(),
-        last_jiffies(0)
-#endif
-    {
-    }
+    process_t();
     
-    ~process_t()
-    {
-        if (this->next != NULL)
-            delete this->next;
-    }
+    ~process_t();
     
 	/** 
 		Type of process. Can be one of \c EXTERNAL, \c
@@ -321,29 +299,8 @@ class job_t
     
     public:
     
-    job_t(job_id_t jobid) :
-        command_str(),
-        command_narrow(),
-        first_process(NULL),
-        pgid(0),
-        tmodes(),
-        job_id(jobid),
-        io(NULL),
-        flags(0)
-    {
-    }
-    
-    ~job_t() {
-        if (first_process != NULL)
-            delete first_process;
-        io_data_t *data = this->io;
-        while (data) {
-            io_data_t *tmp = data->next;
-            delete data;
-            data = tmp;
-        }
-        release_job_id(job_id);
-    }
+    job_t(job_id_t jobid);
+    ~job_t();
     
     /** Returns whether the command is empty. */
     bool command_is_empty() const { return command_str.empty(); }
@@ -389,10 +346,8 @@ class job_t
 	*/
 	const job_id_t job_id;
 	
-	/**
-	   List of all IO redirections for this job. This linked list is allocated via new, and owned by the object, which should delete them.
-	*/
-	io_data_t *io;
+	/** List of all IO redirections for this job. */
+	io_chain_t io;
 
 	/**
 	   Bitset containing information about the job. A combination of the JOB_* constants.
diff --git a/reader.cpp b/reader.cpp
index ecf78d846..777502934 100644
--- a/reader.cpp
+++ b/reader.cpp
@@ -940,7 +940,7 @@ static void run_pager( const wcstring &prefix, int is_quoted, const std::vector<
     wcstring msg;
 	wcstring prefix_esc;
 	char *foo;
-	io_data_t *in;
+
 	wchar_t *escaped_separator;
 	int has_case_sensitive=0;
 
@@ -958,7 +958,7 @@ static void run_pager( const wcstring &prefix, int is_quoted, const std::vector<
                                 is_quoted?L"-q":L"",
                                 prefix_esc.c_str() );
     
-	in= io_buffer_create( 1 );
+    io_data_t *in = io_buffer_create(true);
 	in->fd = 3;
 
 	escaped_separator = escape( COMPLETE_SEP_STR, 1);
@@ -1040,12 +1040,14 @@ static void run_pager( const wcstring &prefix, int is_quoted, const std::vector<
 	
 	term_donate();
 	
-	io_data_t *out = io_buffer_create( 0 );
-	out->next = in;
+	io_data_t *out = io_buffer_create( false );
 	out->fd = 4;
 	
     parser_t &parser = parser_t::principal_parser();
-	parser.eval( cmd, out, TOP);
+    io_chain_t io_chain;
+    io_chain.push_back(out);
+    io_chain.push_back(in);
+	parser.eval( cmd, io_chain, TOP);
 	term_steal();
 
 	io_buffer_read( out );
@@ -2062,7 +2064,7 @@ void reader_run_command( parser_t &parser, const wchar_t *cmd )
 
 	gettimeofday(&time_before, NULL);
 
-	parser.eval( cmd, 0, TOP );
+	parser.eval( cmd, io_chain_t(), TOP );
 	job_reap( 1 );
 
 	gettimeofday(&time_after, NULL);
@@ -3199,7 +3201,7 @@ int reader_search_mode()
    the prompt, using syntax highlighting. This is used for reading
    scripts and init files.
 */
-static int read_ni( int fd, io_data_t *io )
+static int read_ni( int fd, const io_chain_t &io )
 {
     parser_t &parser = parser_t::principal_parser();
 	FILE *in_stream;
@@ -3296,7 +3298,7 @@ static int read_ni( int fd, io_data_t *io )
 	return res;
 }
 
-int reader_read( int fd, io_data_t *io )
+int reader_read( int fd, const io_chain_t &io )
 {
 	int res;
 
diff --git a/reader.h b/reader.h
index 732b06cfb..0c674fd07 100644
--- a/reader.h
+++ b/reader.h
@@ -24,7 +24,7 @@ class history_t;
 /**
   Read commands from \c fd until encountering EOF
 */
-int reader_read( int fd, io_data_t *io);
+int reader_read( int fd, const io_chain_t &io);
 
 /**
   Tell the shell that it should exit after the currently running command finishes.
diff --git a/signal.cpp b/signal.cpp
index 3b6bc2dbd..2c51e9d2f 100644
--- a/signal.cpp
+++ b/signal.cpp
@@ -628,6 +628,18 @@ void signal_handle( int sig, int do_handle )
 	sigaction( sig, &act, 0);
 }
 
+void get_signals_with_handlers(sigset_t *set)
+{
+    sigemptyset(set);
+	for( int i=0; lookup[i].desc ; i++ )
+	{
+        struct sigaction act = {};
+		sigaction(lookup[i].signal, NULL, &act);
+        if (act.sa_handler != SIG_DFL)
+            sigaddset(set, lookup[i].signal);
+	}
+}
+
 void signal_block()
 {
     ASSERT_IS_MAIN_THREAD();
diff --git a/signal.h b/signal.h
index 91bddc920..3bc7527d2 100644
--- a/signal.h
+++ b/signal.h
@@ -6,6 +6,8 @@ The library for various signal related issues
 #ifndef FISH_SIGNALH
 #define FISH_SIGNALH
 
+#include <signal.h>
+
 /**
    Get the integer signal value representing the specified signal, or
    -1 of no signal was found
@@ -55,4 +57,9 @@ void signal_unblock();
 */
 int signal_is_blocked();
 
+/**
+  Returns signals with non-default handlers
+*/
+void get_signals_with_handlers(sigset_t *set);
+
 #endif