added ^E@ string building character

 * allows expansion of Q-Register contents with UNIX shell quoting
 * This especially improves the usefulness of the EC/EG commands as
   we can reliably determine that a TECO string (ie. Q-Register)
   will end up as a single argument to the spawned process.
   A previous workaround was to enclose ^EQ in quotes, but it does
   not work e.g. if the register contains the wrong kind of quotes or
   other magic shell characters.
 * NOTE: In order to be absolutely sure about the runtime behaviour of
   EC plus ^E@, you will have to enable UNIX98 shell emulation in portable
   macros.

3 files changed, 42 insertions, 11 deletions

diff --git a/doc/sciteco.7.template b/doc/sciteco.7.template
index eab26e5..9b31c7d 100644
--- a/doc/sciteco.7.template
+++ b/doc/sciteco.7.template
@@ -1398,9 +1398,12 @@ When \fB^V\fP is not followed by \fB^V\fP, a single character
 .BI ^W c
 Analogous to \fB^V\fP, but upper-cases characters.
 .TP
-.BI ^EQ q
-Expands to the string contents of the Q-Register specified by
-\fIq\fP.
+.BI ^E\(rs q
+Expands to the formatted number stored in the
+numeric part of Q-Register \fIq\fP.
+The number is formatted according to the current
+radix and exactly the same as the backslash (\fB\(rs\fP)
+command would format it.
 Currently, long Q-Register names have a separate independant
 level of string building character processing, allowing you
 to build Q-Register names whose content is then expanded.
@@ -1411,12 +1414,19 @@ part of Q-Register \fIq\fP.
 For instance if register \(lqA\(rq contains the code 66,
 \(lq^EUa\(rq expands to the character \(lqB\(rq.
 .TP
-.BI ^E\(rs q
-Expands to the formatted number stored in the
-numeric part of Q-Register \fIq\fP.
-The number is formatted according to the current
-radix and exactly the same as the backslash (\fB\(rs\fP)
-command would format it.
+.BI ^EQ q
+Expands to the string contents of the Q-Register specified by
+\fIq\fP.
+.TP
+.BI ^E@ q
+Expands to the quoted string contents of the Q-Register
+specified by \fIq\fP.
+The quoting will be such that an UNIX98 \(lq/bin/sh\(rq will
+interpret the quoted string like the original contents of
+\fIq\fP.
+This is useful when generating UNIX shell code or when passing
+registers with unknown contents as parameters to external
+commands using the \fBEC\fP command.
 .TP
 .BI ^E c
 All remaining \fB^E\fP combinations are passed down
diff --git a/src/parser.cpp b/src/parser.cpp
index f05f167..941db49 100644
--- a/src/parser.cpp
+++ b/src/parser.cpp
@@ -388,6 +388,7 @@ bool
 StringBuildingMachine::input(gchar chr, gchar *&result)
 {
 	QRegister *reg;
+	gchar *str;
 
 	switch (mode) {
 	case MODE_UPPER:
@@ -450,13 +451,17 @@ StateCtlE:
 		undo.push_obj(qregspec_machine) = new QRegSpecMachine;
 		set(&&StateCtlENum);
 		break;
+	case 'U':
+		undo.push_obj(qregspec_machine) = new QRegSpecMachine;
+		set(&&StateCtlEU);
+		break;
 	case 'Q':
 		undo.push_obj(qregspec_machine) = new QRegSpecMachine;
 		set(&&StateCtlEQ);
 		break;
-	case 'U':
+	case '@':
 		undo.push_obj(qregspec_machine) = new QRegSpecMachine;
-		set(&&StateCtlEU);
+		set(&&StateCtlEQuote);
 		break;
 	default:
 		result = (gchar *)g_malloc(3);
@@ -497,6 +502,17 @@ StateCtlEQ:
 	result = reg->get_string();
 	return true;
 
+StateCtlEQuote:
+	if (!qregspec_machine->input(chr, reg))
+		return false;
+
+	undo.push_obj(qregspec_machine) = NULL;
+	set(StateStart);
+	str = reg->get_string();
+	result = g_shell_quote(str);
+	g_free(str);
+	return true;
+
 StateEscaped:
 	set(StateStart);
 	result = String::chrdup(chr);
diff --git a/src/spawn.cpp b/src/spawn.cpp
index 9ea3919..0722180 100644
--- a/src/spawn.cpp
+++ b/src/spawn.cpp
@@ -209,6 +209,11 @@ parse_shell_command_line(const gchar *cmdline, GError **error)
  * \(lq0,128ED\(rq, and is recommended when writing cross-platform
  * macros using the EC command.
  *
+ * When using an UNIX-compatible shell or the UNIX98 shell emulation,
+ * you might want to use the \fB^E@\fP string-building character
+ * to pass Q-Register contents reliably as single arguments to
+ * the spawned process.
+ *
  * The spawned process inherits both \*(ST's current working
  * directory and its environment variables.
  * More precisely, \*(ST uses its environment registers