From 19a4b38f2bcfe6a1809bdcbcd23fdec15c3cf771 Mon Sep 17 00:00:00 2001
From: Laurent Bercot <ska-skaware@skarnet.org>
Date: Sun, 1 Jun 2025 10:03:28 +0000
Subject:  Add config test option to mdevd (thanks lanodan)

Signed-off-by: Laurent Bercot <ska@appnovation.com>
---
 AUTHORS           | 3 +++
 doc/mdevd.html    | 5 ++++-
 src/mdevd/mdevd.c | 6 ++++--
 3 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/AUTHORS b/AUTHORS
index 33d961a..797c469 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -1,6 +1,9 @@
 Main author:
   Laurent Bercot <ska-skaware@skarnet.org>
 
+Contributors:
+ Haelwenn (lanodan) Monnier <contact@hacktivis.me>
+
 Thanks to:
   Rob Landley <rob@landley.net>
   Natanael Copa <ncopa@alpinelinux.org>
diff --git a/doc/mdevd.html b/doc/mdevd.html
index 7c2a869..4b814de 100644
--- a/doc/mdevd.html
+++ b/doc/mdevd.html
@@ -49,7 +49,7 @@ to running mdevd over mdev. </li>
 <h2> Interface </h2>
 
 <pre>
-     mdevd [ -v <em>verbosity</em> ] [ -D <em>notif</em> ] [ -I <em>intake</em> ] [ -o <em>outputfd</em> ] [ -I <em>intake</em> ] [ -O <em>nlgroups</em> ] [ -b <em>kbufsz</em> ] [ -f <em>conffile</em> ] [ -n ] [ -s <em>slashsys</em> ] [ -d <em>slashdev</em> ] [ -F <em>fwbase</em> ] [ -C ]
+     mdevd [ -v <em>verbosity</em> ] [ -D <em>notif</em> ] [ -I <em>intake</em> ] [ -o <em>outputfd</em> ] [ -I <em>intake</em> ] [ -O <em>nlgroups</em> ] [ -b <em>kbufsz</em> ] [ -f <em>conffile</em> ] [ -n | -N ] [ -s <em>slashsys</em> ] [ -d <em>slashdev</em> ] [ -F <em>fwbase</em> ] [ -C ]
 </pre>
 
 <ul>
@@ -126,6 +126,9 @@ from mdevd at coldplug time, try increasing this number. </li>
  <li> <tt>-n</tt>&nbsp;: dry run. mdevd will not create or delete
 device nodes, and it will not spawn commands. Instead, it will print to stdout
 the actions it would have performed. </li>
+ <li> <tt>-N</tt>&nbsp;: configuration file test. mdevd will not run, it will
+only parse its configuration file and exit 0 on success or nonzero (with an
+error message) on failure. This option overrides, and is overridden by, <tt>-n</tt>. </li>
  <li> <tt>-f</tt>&nbsp;<em>conffile</em>&nbsp;: read the configuration
 file from <em>conffile</em>. Default is <tt>/etc/mdev.conf</tt>.
 <em>conffile</em> must be an absolute path. </li>
diff --git a/src/mdevd/mdevd.c b/src/mdevd/mdevd.c
index f5222f7..c34bf58 100644
--- a/src/mdevd/mdevd.c
+++ b/src/mdevd/mdevd.c
@@ -43,7 +43,7 @@
 #include <mdevd/config.h>
 #include "mdevd-internal.h"
 
-#define USAGE "mdevd [ -v verbosity ] [ -D notif ] [ -I intake ] [ -o outputfd ] [ -O nlgroups ] [ -b kbufsz ] [ -f conffile ] [ -n ] [ -s slashsys ] [ -d slashdev ] [ -F fwbase ] [ -C ]"
+#define USAGE "mdevd [ -v verbosity ] [ -D notif ] [ -I intake ] [ -o outputfd ] [ -O nlgroups ] [ -b kbufsz ] [ -f conffile ] [ -n | -N ] [ -s slashsys ] [ -d slashdev ] [ -F fwbase ] [ -C ]"
 #define dieusage() strerr_dieusage(100, USAGE)
 
 #define CONFBUFSIZE 8192
@@ -915,11 +915,12 @@ int main (int argc, char const *const *argv)
     subgetopt l = SUBGETOPT_ZERO ;
     for (;;)
     {
-      int opt = subgetopt_r(argc, argv, "nv:D:I:o:O:b:f:s:d:F:C", &l) ;
+      int opt = subgetopt_r(argc, argv, "nNv:D:I:o:O:b:f:s:d:F:C", &l) ;
       if (opt == -1) break ;
       switch (opt)
       {
         case 'n' : dryrun = 1 ; break ;
+        case 'N' : dryrun = 2 ; break ;
         case 'v' : if (!uint0_scan(l.arg, &verbosity)) dieusage() ; break ;
         case 'D' : if (!uint0_scan(l.arg, &notif)) dieusage() ; break ;
         case 'I' : if (!uint0_scan(l.arg, &intake)) dieusage() ; break ;
@@ -1023,6 +1024,7 @@ int main (int argc, char const *const *argv)
       memset(script, 0, scriptlen * sizeof(scriptelem)) ;
       script[scriptlen++] = scriptelem_catchall ;
       script_secondpass(storage, script, envmatch) ;
+      if (dryrun == 2) break ;
       cont = 2 ;
       if (docoldplug)
       {
-- 
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