option to let mtp's keep stdout/stderr

README.md

@@ -826,8 +826,11 @@ copyparty can invoke external programs to collect additional metadata for files
 * "audio file" also means videos btw, as long as there is an audio stream
 * `-mtp ext=an,~/bin/file-ext.py` runs `~/bin/file-ext.py` to get the `ext` tag only if file is not audio (`an`)
 * `-mtp arch,built,ver,orig=an,eexe,edll,~/bin/exe.py` runs `~/bin/exe.py` to get properties about windows-binaries only if file is not audio (`an`) and file extension is exe or dll
-
-you can control how the parser is killed if it times out with option `kt` killing the entire process tree (default), `km` just the main process, or `kn` let it continue running until copyparty is terminated
+* if you want to daisychain parsers, use the `p` flag to set processing order
+  * `-mtp foo=p1,~/a.py` runs before `-mtp foo=p2,~/b.py` and will forward all the tags detected so far as json to the stdin of b.py
+* option `c0` disables capturing of stdout/stderr, so copyparty will not receive any tags from the process at all -- instead the invoked program is free to print whatever to the console, just using copyparty as a launcher
+  * `c1` captures stdout only, `c2` only stderr, and `c3` (default) captures both
+* you can control how the parser is killed if it times out with option `kt` killing the entire process tree (default), `km` just the main process, or `kn` let it continue running until copyparty is terminated
 
 if something doesn't work, try `--mtag-v` for verbose error messages
 
@@ -846,7 +849,7 @@ that'll run the command `notify-send` with the path to the uploaded file as the
 
 note that it will only trigger on new unique files, not dupes
 
-and it will occupy the parsing threads, so fork anything expensive, or if you want to intentionally queue/singlethread you can combine it with `--mtag-mt 1`
+and it will occupy the parsing threads, so fork anything expensive (or set `kn` to have copyparty fork it for you) -- otoh if you want to intentionally queue/singlethread you can combine it with `--mtag-mt 1`
 
 if this becomes popular maybe there should be a less janky way to do it actually
 

bin/mtag/very-bad-idea.py

@@ -16,7 +16,7 @@ goes without saying, but this is HELLA DANGEROUS,
   GIVES RCE TO ANYONE WHO HAVE UPLOAD PERMISSIONS
 
 example copyparty config to use this:
-  --urlform save,get -v.::w:c,e2d,e2t,mte=+a1:c,mtp=a1=ad,kn,bin/mtag/very-bad-idea.py
+  --urlform save,get -v.::w:c,e2d,e2t,mte=+a1:c,mtp=a1=ad,kn,c0,bin/mtag/very-bad-idea.py
 
 recommended deps:
   apt install xdotool libnotify-bin

copyparty/mtag.py

@@ -45,6 +45,7 @@ class MParser(object):
         self.timeout = 30
         self.force = False
         self.kill = "t"  # tree; all children recursively
+        self.capture = 3  # outputs to consume
         self.audio = "y"
         self.pri = 0  # priority; higher = later
         self.ext = []
@@ -72,6 +73,10 @@ class MParser(object):
                 self.kill = arg[1:]  # [t]ree [m]ain [n]one
                 continue
 
+            if arg.startswith("c"):
+                self.capture = int(arg[1:])  # 0=none 1=stdout 2=stderr 3=both
+                continue
+
             if arg == "f":
                 self.force = True
                 continue
@@ -519,7 +524,12 @@ class MTag(object):
                 if parser.bin.endswith(".py"):
                     cmd = [sys.executable] + cmd
 
-                args = {"env": env, "timeout": parser.timeout, "kill": parser.kill}
+                args = {
+                    "env": env,
+                    "timeout": parser.timeout,
+                    "kill": parser.kill,
+                    "capture": parser.capture,
+                }
 
                 if parser.pri:
                     zd = oth_tags.copy()

copyparty/util.py

@@ -1862,12 +1862,16 @@ def runcmd(
     argv: Union[list[bytes], list[str]], timeout: Optional[int] = None, **ka: Any
 ) -> tuple[int, str, str]:
     kill = ka.pop("kill", "t")  # [t]ree [m]ain [n]one
+    capture = ka.pop("capture", 3)  # 0=none 1=stdout 2=stderr 3=both
 
     sin = ka.pop("sin", None)
     if sin:
         ka["stdin"] = sp.PIPE
 
-    p = sp.Popen(argv, stdout=sp.PIPE, stderr=sp.PIPE, **ka)
+    cout = sp.PIPE if capture in [1, 3] else None
+    cerr = sp.PIPE if capture in [2, 3] else None
+
+    p = sp.Popen(argv, stdout=cout, stderr=cerr, **ka)
     if not timeout or PY2:
         stdout, stderr = p.communicate(sin)
     else:
@@ -1887,8 +1891,8 @@ def runcmd(
                 stdout = b""
                 stderr = b""
 
-    stdout = stdout.decode("utf-8", "replace")
-    stderr = stderr.decode("utf-8", "replace")
+    stdout = stdout.decode("utf-8", "replace") if cout else b""
+    stderr = stderr.decode("utf-8", "replace") if cerr else b""
 
     rc = p.returncode
     if rc is None: