pidfile support backport to 1.92

--- transmission-1.92/daemon/daemon.orig.c.v1.92	2010-05-20 23:15:45.686493465 -0400
+++ transmission-1.92/daemon/daemon.c	2010-05-20 23:39:59.187742392 -0400
@@ -43,6 +43,7 @@
 static tr_bool paused = FALSE;
 static tr_bool closing = FALSE;
 static tr_session * mySession = NULL;
+static const char * pid_filename = NULL;
 
 /***
 ****  Config File
@@ -98,6 +99,7 @@
     { 'r', "rpc-bind-address", "Where to listen for RPC connections", "r", 1, "<ipv4 address>" },
     { 953, "global-seedratio", "All torrents, unless overridden by a per-torrent setting, should seed until a specific ratio", "gsr", 1, "ratio" },
     { 954, "no-global-seedratio", "All torrents, unless overridden by a per-torrent setting, should seed regardless of ratio", "GSR", 0, NULL },
+    { 'x', "pid-file", "Enable PID file", "x", 1, "<pid-file>" },
     { 0, NULL, NULL, NULL, 0, NULL }
 };
 
@@ -288,6 +290,7 @@
     const char * configDir = NULL;
     dtr_watchdir * watchdir = NULL;
     FILE * logfile = NULL;
+    tr_bool pidfile_created = FALSE;
 
     signal( SIGINT, gotsig );
     signal( SIGTERM, gotsig );
@@ -388,6 +391,8 @@
 	    case 954:
 		      tr_bencDictAddBool( &settings, TR_PREFS_KEY_RATIO_ENABLED, FALSE );
 		      break;
+      case 'x': pid_filename = optarg;
+          break;
             default:  showUsage( );
                       break;
         }
@@ -423,6 +428,20 @@
     tr_ninf( NULL, "Using settings from \"%s\"", configDir );
     tr_sessionSaveSettings( mySession, configDir, &settings );
 
+    /* create the pidfile */
+    if( pid_filename != NULL ) {
+        FILE * fp = fopen( pid_filename, "w+" );
+        if( fp != NULL ) 
+        {
+            fprintf( fp, "%d", (int)getpid() );
+            fclose( fp );
+            tr_inf( "Saved pidfile \"%s\"", pid_filename );
+            pidfile_created = TRUE;
+        }
+        else
+          tr_err( "Unable to save pidfile \"%s\": %s", pid_filename, strerror( errno ) );
+    }
+
     if( tr_bencDictFindBool( &settings, TR_PREFS_KEY_RPC_AUTH_REQUIRED, &boolVal ) && boolVal )
         tr_ninf( MY_NAME, "requiring authentication" );
 
@@ -454,7 +473,7 @@
 
 #ifdef HAVE_SYSLOG
     if( !foreground )
-        openlog( MY_NAME, LOG_CONS, LOG_DAEMON );
+        openlog( MY_NAME, LOG_CONS|LOG_PID, LOG_DAEMON );
 #endif
 
     while( !closing ) {
@@ -479,6 +498,8 @@
     printf( " done.\n" );
 
     /* cleanup */
+    if( pidfile_created )
+        remove( pid_filename );
     tr_bencFree( &settings );
     return 0;
 }