main: add --check-config command line option

CHANGELOG.md

@@ -21,6 +21,7 @@
   **scrollback-indicator-format** options in `footrc`
   (https://codeberg.org/dnkl/foot/issues/42).
 * Key bindings in _scollback search_ mode are now configurable.
+* `--check-config` command line option.
 
 
 ### Deprecated

completions/zsh/_foot

@@ -3,6 +3,7 @@
 _arguments \
     -s -S -C \
     '(-c --config)'{-c,--config}'[path to configuration file (XDG_CONFIG_HOME/footrc)]:config:_files' \
+    '--check-config[verify configuration and exit with 0 if ok, otherwise exit with 1]' \
     '(-f --font)'{-f,--font}'[font name and style in fontconfig format (monospace)]:font:->fonts' \
     '(-t --term)'{-t,--term}'[value to set the environment variable TERM to (foot)]:term:->terms' \
     '--title[initial window title]:()' \

doc/foot.1.scd

@@ -15,6 +15,10 @@ arguments, to execute (instead of the default shell).
 *-c*,*--config*=_PATH_
 	Path to configuration file. Default: *XDG_CONFIG_HOME/footrc*.
 
+*--check-config*
+	Verify configuration and then exit with 0 if ok, otherwise exit
+	with 1.
+
 *-f*,*--font*=_FONT_
 	Comma separated list of fonts to use, in fontconfig format (see
 	*FONT FORMAT*).

main.c

@@ -46,6 +46,7 @@ print_usage(const char *prog_name)
         "\n"
         "Options:\n"
         "  -c,--config=PATH                      load configuration from PATH (XDG_CONFIG_HOME/footrc)\n"
+        "     --check-config                     verify configuration, exit with 0 if ok, otherwise exit with 1\n"
         "  -f,--font=FONT                        comma separated list of fonts in fontconfig format (monospace)\n"
         "  -t,--term=TERM                        value to set the environment variable TERM to (foot)\n"
         "     --title=TITLE                      initial window title (foot)\n"
@@ -142,6 +143,7 @@ main(int argc, char *const *argv)
 
     static const struct option longopts[] =  {
         {"config",               required_argument, NULL, 'c'},
+        {"check-config",         no_argument,       NULL, 'C'},
         {"term",                 required_argument, NULL, 't'},
         {"title",                required_argument, NULL, 'T'},
         {"app-id",               required_argument, NULL, 'a'},
@@ -161,6 +163,7 @@ main(int argc, char *const *argv)
         {NULL,                   no_argument,       NULL,   0},
     };
 
+    bool check_config = false;
     const char *conf_path = NULL;
     const char *conf_term = NULL;
     const char *conf_title = NULL;
@@ -181,7 +184,7 @@ main(int argc, char *const *argv)
     bool log_syslog = true;
 
     while (true) {
-        int c = getopt_long(argc, argv, "+c:t:a:Lf:g:s::Pp:l::Svh", longopts, NULL);
+        int c = getopt_long(argc, argv, "+c:Ct:a:Lf:g:s::Pp:l::Svh", longopts, NULL);
         if (c == -1)
             break;
 
@@ -190,6 +193,10 @@ main(int argc, char *const *argv)
             conf_path = optarg;
             break;
 
+        case 'C':
+            check_config = true;
+            break;
+
         case 't':
             conf_term = optarg;
             break;
@@ -320,6 +327,11 @@ main(int argc, char *const *argv)
         return ret;
     }
 
+    if (check_config) {
+        config_free(conf);
+        return EXIT_SUCCESS;
+    }
+
     setlocale(LC_CTYPE, "");
     LOG_INFO("locale: %s", setlocale(LC_CTYPE, NULL));
     if (!locale_is_utf8()) {