mu extract/view/verify: allow reading message from stdin

Fixes #1463.

NEWS.org

@@ -3,11 +3,17 @@
 
 * 1.11.x (unreleased development build)
 
+*** mu
+
+    - ~mu~ commands ~extract~, ~verify~ and ~view~ can now read the message from
+       standard input; see their man-pages for details
+
 *** mu4e
 
     - experimental: support folding message threads (with TAB / S-TAB).
       See the [[info:mu4e:Folding threads][manual entry]] for further details.
 
+
 * 1.10 (released on March 26, 2023)
 
 *** mu

man/mu-extract.1.org

@@ -8,7 +8,7 @@
 
 * SYNOPSIS
 
-*mu [common-options] extract [options] <file>*
+*mu [common-options] extract [options] [<file>]*
 
 *mu [common-options] extract [options] <file> <pattern>*
 
@@ -30,6 +30,10 @@ Without any options, *mu extract* simply outputs the list of leaf MIME-parts in
 the message. Only 'leaf' MIME-parts (including RFC822 attachments) are
 considered, *multipart/** etc. are ignored.
 
+Without a filename parameter, ~mu extract~ reads a message from standard-input. In
+that case, you cannot use the second, ~<pattern>~ parameter as this would be
+ambiguous; instead, use the ~--matches~ option.
+
 * EXTRACT OPTIONS
 
 ** -a, --save-attachments
@@ -56,6 +60,11 @@ by default, ~mu~ transforms the attachment filenames a bit (such as by replacing
 spaces by dashes); with this option, leave that to the minimum for creating
 a legal filename in the target directory.
 
+** --matches=<pattern>
+Attachments with filenames matching the pattern will be extracted. The regular
+expressions are basic PCRE, and are case-sensitive by default; see *pcre(3)* for
+more details.
+
 ** --play
 Try to 'play' (open) the attachment with the default application for the
 particular file type. On MacOS, this uses the *open* program, on other platforms
@@ -87,6 +96,11 @@ To extract an mp3-file, and play it in the default mp3-playing application:
 $ mu extract --play msgfile 'whoopsididitagain.mp3'
 #+end_example
 
+when reading from standard-input, you need ~--matches~, so:
+#+begin_example
+$ cat msgfile | mu extract --play --matches 'whoopsididitagain.mp3'
+#+end_example
+
 #+include: "prefooter.inc" :minlevel 1
 
 * SEE ALSO

man/mu-verify.1.org

@@ -7,7 +7,7 @@ mu verify - verify message signatures and display information about them
 
 * SYNOPSIS
 
-*mu [common-options] verify [options] <msgfile>*
+*mu [common-options] verify [options] [<file> ... ]*
 
 * DESCRIPTION
 
@@ -15,6 +15,9 @@ mu verify - verify message signatures and display information about them
 signatures) and displaying information about them. The sub-command works on
 message files, and does not require the message to be indexed in the database.
 
+If no message file is provided, the command expects the message on
+standard-input.
+
 * VERIFY OPTIONS
 
 ** -r, --auto-retrieve

man/mu-view.1.org

@@ -7,7 +7,7 @@ mu view - display an e-mail message file
 
 * SYNOPSIS
 
-mu [common options] view [options] <file> [<files>]
+mu [common options] view [options] [<file> ...]
 
 * DESCRIPTION
 
@@ -17,6 +17,9 @@ message files and does =not= require the message to be indexed in the database.
 The command shows some common headers (From:, To:, Cc:, Bcc:, Subject: and
 Date:), the list of attachments and the plain-text body of the message (if any).
 
+If no message file is provided, the command expects the message on
+standard-input.
+
 * VIEW OPTIONS
 
 ** --summary-len=<number>

mu/mu-cmd-extract.cc

@@ -49,15 +49,11 @@ save_part(const Message::Part& part, size_t idx, const Options& opts)
 }
 
 static Result<void>
-save_parts(const std::string& path, const std::string& filename_rx,
+save_parts(const Message& message, const std::string& filename_rx,
 	   const Options& opts)
 {
-	auto message{Message::make_from_path(path, message_options(opts.extract))};
-	if (!message)
-		return Err(std::move(message.error()));
-
 	size_t partnum{}, saved_num{};
-	for (auto&& part: message->parts()) {
+	for (auto&& part: message.parts()) {
 		++partnum;
 		// should we extract this part?
 		const auto do_extract = std::invoke([&]() {
@@ -134,15 +130,11 @@ show_part(const MessagePart& part, size_t index, bool color)
 }
 
 static Mu::Result<void>
-show_parts(const std::string& path, const Options& opts)
+show_parts(const Message& message, const Options& opts)
 {
-	auto msg_res{Message::make_from_path(path, message_options(opts.extract))};
-	if (!msg_res)
-		return Err(std::move(msg_res.error()));
-
 	size_t index{};
 	g_print("MIME-parts in this message:\n");
-	for (auto&& part: msg_res->parts())
+	for (auto&& part: message.parts())
 		show_part(part, ++index, !opts.nocolor);
 
 	return Ok();
@@ -151,15 +143,29 @@ show_parts(const std::string& path, const Options& opts)
 Mu::Result<void>
 Mu::mu_cmd_extract(const Options& opts)
 {
-	if (opts.extract.parts.empty() &&
-	    !opts.extract.save_attachments && !opts.extract.save_all &&
-	    opts.extract.filename_rx.empty())
-		return show_parts(opts.extract.message, opts); /* show, don't save */
+	auto message = std::invoke([&]()->Result<Message>{
+		const auto mopts{message_options(opts.extract)};
+		if (!opts.extract.message.empty())
+			return Message::make_from_path(opts.extract.message, mopts);
+
+		const auto msgtxt = read_from_stdin();
+		if (!msgtxt)
+			return Err(msgtxt.error());
+		else
+			return Message::make_from_text(*msgtxt, {}, mopts);
+	});
+
+	if (!message)
+		return Err(message.error());
+	else if (opts.extract.parts.empty() &&
+		 !opts.extract.save_attachments && !opts.extract.save_all &&
+		 opts.extract.filename_rx.empty())
+		return show_parts(*message, opts); /* show, don't save */
 
 	if (!check_dir(opts.extract.targetdir, false/*!readable*/, true/*writeable*/))
 		return Err(Error::Code::File,
 			   "target '%s' is not a writable directory",
 			   opts.extract.targetdir.c_str());
 
-	return save_parts(opts.extract.message, opts.extract.filename_rx, opts);
+	return save_parts(*message, opts.extract.filename_rx, opts);
 }

mu/mu-cmd.cc

@@ -36,6 +36,7 @@
 #include "message/mu-mime-object.hh"
 
 #include "utils/mu-error.hh"
+#include "utils/mu-utils-file.hh"
 #include "utils/mu-utils.hh"
 #include "message/mu-message.hh"
 
@@ -152,19 +153,15 @@ view_msg_plain(const Message& message, const Options& opts)
 }
 
 static Mu::Result<void>
-handle_msg(const std::string& fname, const Options& opts)
+handle_msg(const Message& message, const Options& opts)
 {
 	using Format = Options::View::Format;
 
-	auto message{Message::make_from_path(fname, message_options(opts.view))};
-	if (!message)
-		return Err(message.error());
-
 	switch (opts.view.format) {
 	case Format::Plain:
-		return view_msg_plain(*message, opts);
+		return view_msg_plain(message, opts);
 	case Format::Sexp:
-		return view_msg_sexp(*message, opts);
+		return view_msg_sexp(message, opts);
 	default:
 		g_critical("bug: should not be reached");
 		return Err(Error::Code::Internal, "error");
@@ -175,13 +172,29 @@ static Mu::Result<void>
 cmd_view(const Options& opts)
 {
 	for (auto&& file: opts.view.files) {
-		if (auto res = handle_msg(file, opts); !res)
+		auto message{Message::make_from_path(
+				file, message_options(opts.view))};
+		if (!message)
+			return Err(message.error());
+
+		if (auto res = handle_msg(*message, opts); !res)
 			return res;
 		/* add a separator between two messages? */
 		if (opts.view.terminate)
 			g_print("%c", VIEW_TERMINATOR);
 	}
 
+	// no files? read from stding
+	if (opts.view.files.empty()) {
+		const auto msgtxt = read_from_stdin();
+		if (!msgtxt)
+			return Err(msgtxt.error());
+		auto message = Message::make_from_text(*msgtxt,{}, message_options(opts.view));
+		if (!message)
+			return Err(message.error());
+		else
+			return handle_msg(*message, opts);
+	}
 	return Ok();
 }
 
@@ -312,6 +325,35 @@ verify(const MimeMultipartSigned& sigpart, const Options& opts)
 	return valid;
 }
 
+
+static bool
+verify_message(const Message& message, const Options& opts, const std::string& name)
+{
+	if (none_of(message.flags() & Flags::Signed)) {
+		if (!opts.quiet)
+			g_print("%s: no signed parts found\n", name.c_str());
+		return false;
+	}
+
+	bool verified{true}; /* innocent until proven guilty */
+	for(auto&& part: message.parts()) {
+
+		if (!part.is_signed())
+			continue;
+
+		const auto& mobj{part.mime_object()};
+		if (!mobj.is_multipart_signed())
+			continue;
+
+		if (!verify(MimeMultipartSigned(mobj), opts))
+			verified = false;
+	}
+
+	return verified;
+}
+
+
+
 static Mu::Result<void>
 cmd_verify(const Options& opts)
 {
@@ -325,29 +367,22 @@ cmd_verify(const Options& opts)
 			return Err(message.error());
 
 		if (!opts.quiet && opts.verify.files.size() > 1)
-			g_print("verifying %sn\n", file.c_str());
+			g_print("verifying %s\n", file.c_str());
 
-		if (none_of(message->flags() & Flags::Signed)) {
-			if (!opts.quiet)
-				g_print("%s: no signed parts found\n", file.c_str());
-			continue;
-		}
+		if (!verify_message(*message, opts, file))
+			all_ok = false;
+	}
 
-		bool verified{true}; /* innocent until proven guilty */
-		for(auto&& part: message->parts()) {
+	// when no messages provided, read from stdin
+	if (opts.verify.files.empty()) {
+		const auto msgtxt = read_from_stdin();
+		if (!msgtxt)
+			return Err(msgtxt.error());
+		auto message{Message::make_from_text(*msgtxt, {}, mopts)};
+		if (!message)
+			return Err(message.error());
 
-			if (!part.is_signed())
-				continue;
-
-			const auto& mobj{part.mime_object()};
-			if (!mobj.is_multipart_signed())
-				continue;
-
-			if (!verify(MimeMultipartSigned(mobj), opts))
-				verified = false;
-		}
-
-		all_ok = all_ok && verified;
+		all_ok = verify_message(*message, opts, "<stdin>");
 	}
 
 	if (all_ok)

mu/mu-options.cc

@@ -223,16 +223,27 @@ sub_extract(CLI::App& sub, Options& opts)
 		       "Target directory for saving")
 		->type_name("<dir>")
 		->default_str("<current>")->default_val(".");
-	sub.add_option("message", opts.extract.message,
-		       "Path to message file")->required()
-		->type_name("<message-path>");
 	sub.add_flag("--uncooked,-u", opts.extract.uncooked,
 		       "Avoid massaging extracted file-names");
+	// optional; otherwise use standard-input
+	sub.add_option("message-path", opts.extract.message,
+		       "Path to message file")
+		->type_name("<message-path>");
+
+	sub.add_option("--matches", opts.extract.filename_rx,
+		       "Regular expression for files to save")
+		->type_name("<filename-rx>")
+		->excludes("--parts")
+		->excludes("--save-attachments")
+		->excludes("--save-all");
+
+	// backward compat: filename-rx as non-option
 	sub.add_option("filename-rx", opts.extract.filename_rx,
 		       "Regular expression for files to save")
 		->type_name("<filename-rx>")
 		->excludes("--parts")
 		->excludes("--save-attachments")
+		->excludes("--matches")
 		->excludes("--save-all");
 }
 
@@ -421,10 +432,10 @@ sub_verify(CLI::App& sub, Options& opts)
 {
 	sub_crypto(sub, opts.verify);
 
-	sub.add_option("files", opts.verify.files,
+	// optional; otherwise use standard-input
+	sub.add_option("message-paths", opts.verify.files,
 		       "Message files to verify")
-		->type_name("<message-file>")
-		->required();
+		->type_name("<message-path>");
 }
 
 static void
@@ -460,10 +471,10 @@ sub_view(CLI::App& sub, Options& opts)
 	sub.add_flag("--terminate", opts.view.terminate,
 		     "Insert form-feed after each message");
 
-	sub.add_option("files", opts.view.files,
+	// optional; otherwise use standard-input
+	sub.add_option("message-paths", opts.view.files,
 		       "Message files to view")
-		->type_name("<file>")
-		->required();
+		->type_name("<message-path>");
 }