[systemd-devel] [PATCH] systemctl: Implement "info" and "doc" commands, similar to "man"

[Gergely Nagy]

Similar to systemctl man, implement the info and doc commands. The
former will open the appropriate info page, the latter will open any
http (or https) documentation via xdg-open.

Signed-off-by: Gergely Nagy <algernon at balabit.hu>
---
 man/systemctl.xml         |   23 +++++++++++++++++
 src/systemctl/systemctl.c |   59 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 82 insertions(+), 0 deletions(-)

diff --git a/man/systemctl.xml b/man/systemctl.xml
index 34a3ea8..5878d7a 100644
--- a/man/systemctl.xml
+++ b/man/systemctl.xml
@@ -642,6 +642,29 @@
                                 is shown.</para></listitem>
                         </varlistentry>
                         <varlistentry>
+                                <term><command>info [NAME...|PID...]</command></term>
+
+                                <listitem><para>Show info pages for
+                                one or more units, if available. If a
+                                PID is passed the info pages for the
+                                unit the process of the PID belongs to
+                                is shown.</para></listitem>
+                        </varlistentry>
+                        <varlistentry>
+                                <term><command>doc [NAME...|PID...]</command></term>
+
+                                <listitem><para>Show online documentation for
+                                one or more units, if available. If a
+                                PID is passed the documentation for the
+                                unit the process of the PID belongs to
+                                is shown.</para>
+
+                                <para>Only documentation available
+                                on-line via http will be considered,
+                                and will be opened with
+                                <literal>xdg-open</literal></para></listitem>
+                        </varlistentry>
+                        <varlistentry>
                                 <term><command>reset-failed [NAME...]</command></term>
 
                                 <listitem><para>Reset the
diff --git a/src/systemctl/systemctl.c b/src/systemctl/systemctl.c
index f65bd2f..a0a6d07 100644
--- a/src/systemctl/systemctl.c
+++ b/src/systemctl/systemctl.c
@@ -2525,6 +2525,57 @@ static void man_status_info(UnitStatusInfo *i) {
         }
 }
 
+static void simple_status_info(const char *cmd, const char *prefix, bool strip_prefix, UnitStatusInfo *i) {
+        char **p;
+
+        assert(i);
+
+        if (!i->documentation) {
+                log_info("Documentation for %s not known.", i->id);
+                return;
+        }
+
+        STRV_FOREACH(p, i->documentation) {
+
+                if (startswith(*p, prefix)) {
+                        pid_t pid;
+                        char *page;
+                        const char *args[3] = { cmd, NULL, NULL };
+
+                        if (strip_prefix) {
+                                page = *p + strlen(prefix);
+                        } else
+                                page = *p;
+
+                        args[1] = page;
+
+                        pid = fork();
+                        if (pid < 0) {
+                                log_error("Failed to fork: %m");
+                                continue;
+                        }
+
+                        if (pid == 0) {
+                                /* Child */
+                                execvp(args[0], (char **) args);
+                                log_error("Failed to execute %s: %m", cmd);
+                                _exit(EXIT_FAILURE);
+                        }
+
+                        wait_for_terminate(pid, NULL);
+                } else
+                        log_info("Can't show %s.", *p);
+        }
+}
+
+static void info_status_info(UnitStatusInfo *i) {
+        simple_status_info("info", "info:", true, i);
+}
+
+static void doc_status_info(UnitStatusInfo *i) {
+        simple_status_info("xdg-open", "http", false, i);
+}
+
 static int status_property(const char *name, DBusMessageIter *iter, UnitStatusInfo *i) {
 
         assert(name);
@@ -3022,6 +3073,10 @@ static int show_one(const char *verb, DBusConnection *bus, const char *path, boo
         if (!show_properties) {
                 if (streq(verb, "man"))
                         man_status_info(&info);
+                else if (streq(verb, "info"))
+                        info_status_info(&info);
+                else if (streq(verb, "doc"))
+                        doc_status_info(&info);
                 else
                         print_status_info(&info);
         }
@@ -4285,6 +4340,8 @@ static int systemctl_help(void) {
                "  show [NAME...|JOB...]           Show properties of one or more\n"
                "                                  units/jobs or the manager\n"
                "  man [NAME...|PID...]            Show manual for one or more units\n"
+               "  info [NAME...|PID...]           Show info pages for one or more units\n"
+               "  doc [NAME...|PID...]            Show on-line documentation for one or more units\n"
                "  reset-failed [NAME...]          Reset failed state for all, one, or more\n"
                "                                  units\n"
                "  load [NAME...]                  Load one or more units\n\n"
@@ -5249,6 +5306,8 @@ static int systemctl_main(DBusConnection *bus, int argc, char *argv[], DBusError
                 { "show",                  MORE,  1, show              },
                 { "status",                MORE,  2, show              },
                 { "man",                   MORE,  2, show              },
+                { "info",                  MORE,  2, show              },
+                { "doc",                   MORE,  2, show              },
                 { "dump",                  EQUAL, 1, dump              },
                 { "dot",                   EQUAL, 1, dot               },
                 { "snapshot",              LESS,  2, snapshot          },
-- 
1.7.9