Implement environment unset and listening on environment changes

doc/manpages/dinit-monitor.8.m4

@@ -1,23 +1,25 @@
 changequote(`@@@',`$$$')dnl
 @@@.TH DINIT\-MONITOR "8" "$$$MONTH YEAR@@@" "Dinit $$$VERSION@@@" "Dinit \- service management system"
 .SH NAME
-dinit\-monitor \- monitor services supervised by Dinit
+dinit\-monitor \- monitor services or environment supervised by Dinit
 .\"
 .SH SYNOPSIS
 .\"
 .PD 0
 .nh
 .HP
 .B dinit-monitor
-[\fIoptions\fR] {\fB\-c\fR \fIcommand\fR, \fB\-\-command\fR \fIcommand\fR} \fIservice-name\fR [\fIservice-name\fR...]
+[\fIoptions\fR] {\fB\-c\fR \fIcommand\fR, \fB\-\-command\fR \fIcommand\fR} \fIservice-or-env\fR [\fIservice-or-env\fR...]
 .\"
 .PD
 .hy
 .\"
 .SH DESCRIPTION
 .\"
-\fBdinit\-monitor\fR is a utility to monitor the state of one or more services managed by the \fBdinit\fR daemon.
-Changes in service state are reported by the execution of the specified command.
+\fBdinit\-monitor\fR is a utility to monitor the state of one or more services or environment managed by the \fBdinit\fR daemon.
+Changes in service or environment state are reported by the execution of the specified command.
+When monitoring environment, positional arguments are not required (all environment will be monitored).
+By default, service events are monitored.
 .\"
 .SH GENERAL OPTIONS
 .TP
@@ -27,6 +29,11 @@ Display brief help text and then exit.
 \fB\-\-version\fR
 Display version and then exit.
 .TP
+\fB\-e\fR, \fB\-\-exit\fR
+Exit after the first command is executed, instead of waiting for more events.
+\fB\-E\fR, \fB\-\-env\fR
+Instead of monitoring the services, monitor changes in the global environment.
+If no environment variables are passed, all environment is monitored.
 \fB\-s\fR, \fB\-\-system\fR
 Control the system init process (this is the default when run as root).
 This option determines the default path to the control socket used to communicate with the \fBdinit\fR daemon
@@ -38,8 +45,8 @@ This option determines the default path to the control socket used to communicat
 (it does not override the \fB\-p\fR option).
 .TP
 \fB\-i\fR, \fB\-\-initial\fR
-Issue the specified command additionally for the initial status of the services (when \fBdinit\-monitor\fR is started).
-Without this option, the command is only executed whenever service status changes.
+Issue the specified command additionally for the initial status of the services or environment (when \fBdinit\-monitor\fR is started).
+Without this option, the command is only executed whenever status changes.
 .TP
 \fB\-\-str\-started\fR \fIstarted-text\fR
 Specify the text used for the substitution of the status in the command (as specified
@@ -53,6 +60,14 @@ by the \fB\-\-command\fR option) when a service stops.
 Specify the text used for the substitution of the status in the command (as specified
 by the \fB\-\-command\fR option) when a service fails to start.
 .TP
+\fB\-\-str\-set\fR \fIset-text\fR
+Specify the text used for the substitution of the status in the command (as specified
+by the \fB\-\-command\fR option) when an environment variable is set.
+.TP
+\fB\-\-str\-unset\fR \fIunset-text\fR
+Specify the text used for the substitution of the status in the command (as specified
+by the \fB\-\-command\fR option) when an environment variable is unset.
+.TP
 \fB\-\-socket\-path\fR \fIsocket-path\fR, \fB\-p\fR \fIsocket-path\fR
 Specify the path to the socket used for communicating with the service manager daemon.
 When not specified, the \fIDINIT_SOCKET_PATH\fR environment variable is read, otherwise
@@ -61,9 +76,11 @@ Dinit's default values are used.
 .SH STATUS REPORT OPTIONS
 .TP
 \fB\-\-command\fR \fIcommand\fR, \fB\-c\fR \fIcommand\fR
-Execute the specified \fIcommand\fR when the service status changes. In \fIcommand\fR, \fB%n\fR
-will be substituted with the service name and \fB%s\fR will be substituted with a textual
-description of the new status (\fBstarted\fR, \fBstopped\fR or \fBfailed\fR). A double percent sign
+Execute the specified \fIcommand\fR when the service status changes.
+In \fIcommand\fR, \fB%n\fR will be substituted with the service or environment variable name,
+\fB%v\fR will be substituted with the environment variable value, and \fB%s\fR will be substituted
+with a textual description of the new status (\fBstarted\fR, \fBstopped\fR or \fBfailed\fR for
+services, \fBset\fR or \fBunset\fR for environment variables). A double percent sign
 (\fB%%\fR) is substituted with a single percent sign character.
 .\"
 .SH OPERATION

doc/manpages/dinitctl.8.m4

@@ -69,6 +69,9 @@ dinitctl \- control services supervised by Dinit
 [\fIoptions\fR] \fBsetenv\fR [\fIname\fR[=\fIvalue\fR] \fI...\fR]
 .HP
 .B dinitctl
+[\fIoptions\fR] \fBunsetenv\fR [\fIname\fR \fI...\fR]
+.HP
+.B dinitctl
 [\fIoptions\fR] \fBcatlog\fR [\fB--clear\fR] \fIservice-name\fR
 .HP
 .B dinitctl
@@ -322,6 +325,10 @@ called in.
 Any subsequently started or restarted service will have these environment variables available.
 This is particularly useful for user services that need access to session information.
 .TP
+\fBunsetenv\fR
+Unset one or more variables in the activation environment.
+Any subsequently started or restarted service will have these environment variables unset.
+.TP
 \fBcatlog\fR
 Show the contents of the log buffer for the named service.
 This is possible only if the log type of the service is set to \fBbuffer\fR.

src/control.cc

@@ -111,6 +111,8 @@ bool control_conn_t::process_packet()
             return process_setenv();
         case cp_cmd::GETALLENV:
             return process_getallenv();
+        case cp_cmd::LISTENENV:
+            return process_listenenv();
         case cp_cmd::SETTRIGGER:
             return process_set_trigger();
         case cp_cmd::CATLOG:
@@ -1076,13 +1078,19 @@ bool control_conn_t::process_setenv()
     envVar = rbuf.extract_string(3, envvar_len);
 
     eq = envVar.find('=');
-    if (!eq || eq == envVar.npos) {
-        // Not found or at the beginning of the string
+    if (eq == envVar.npos) {
+        // Unset the env var
+        main_env.undefine_var(std::move(envVar), true);
+    }
+    else if (eq) {
+        // Regular set
+        main_env.set_var(std::move(envVar), true);
+    }
+    else {
+        // At the beginning of the string
         goto badreq;
     }
 
-    main_env.set_var(std::move(envVar));
-
     // Success response
     if (!queue_packet(okRep, 1)) return false;
 
@@ -1141,6 +1149,17 @@ bool control_conn_t::process_getallenv()
     return true;
 }
 
+bool control_conn_t::process_listenenv()
+{
+    // 1 byte packet type, nothing else
+    rbuf.consume(1);
+
+    main_env.add_listener(this);
+
+    char ack_rep[] = { (char)cp_rply::ACK };
+    return queue_packet(ack_rep, 1);
+}
+
 bool control_conn_t::process_set_trigger()
 {
     // 1 byte packet type
@@ -1468,6 +1487,28 @@ void control_conn_t::service_event(service_record *service, service_event_t even
     }
 }
 
+void control_conn_t::environ_event(environment *env, std::string const &var_and_val, bool overridden) noexcept
+{
+    // packet type (byte) + packet length (byte) + flags byte + data size + data
+    // flags byte can be 1 or 0 for now, 1 if the var was overridden and 0 if fresh
+    constexpr int pktsize = 3 + sizeof(envvar_len_t);
+    envvar_len_t ln = var_and_val.size() + 1;
+    auto *ptr = var_and_val.data();
+
+    try {
+        std::vector<char> pkt;
+        pkt.reserve(pktsize + ln);
+        pkt.push_back((char)cp_info::ENVEVENT);
+        pkt.push_back(pktsize);
+        pkt.push_back(overridden ? 1 : 0);
+        pkt.insert(pkt.end(), (char *)&ln, ((char *)&ln) + sizeof(envvar_len_t));
+        pkt.insert(pkt.end(), ptr, ptr + ln);
+        queue_packet(std::move(pkt));
+    } catch (std::bad_alloc &exc) {
+        do_oom_close();
+    }
+}
+
 bool control_conn_t::queue_packet(const char *pkt, unsigned size) noexcept
 {
     bool was_empty = outbuf.empty();
@@ -1671,6 +1712,7 @@ control_conn_t::~control_conn_t() noexcept
     for (auto p : service_key_map) {
         p.first->remove_listener(this);
     }
+    main_env.remove_listener(this);
 
     active_control_conns--;
 }