Index: code/sys/sys_unix.c
===================================================================
--- code/sys/sys_unix.c	(revision 2080)
+++ code/sys/sys_unix.c	(working copy)
@@ -43,6 +43,8 @@
 // Used to determine where to store user-specific files
 static char homePath[ MAX_OSPATH ] = { 0 };
 
+static qboolean Sys_PathHasCommand(const char *);
+
 /*
 ==================
 Sys_DefaultHomePath
@@ -438,8 +440,59 @@
 	return listCopy;
 }
 
+
 /*
 ==================
+Sys_PathHasCommand
+
+Try to find a command (name only) in a directory from the PATH
+environment variable.
+==================
+*/
+static qboolean Sys_PathHasCommand( const char *command )
+{
+	char try_path[ MAX_OSPATH ];
+	size_t buf_sizeof;
+	char *buf;
+	const char *start;
+	const char *path;
+	char *p;
+	qboolean flag = qfalse;
+
+	path = getenv( "PATH" );
+	if (path == NULL) {
+		return qfalse;
+	}
+
+	buf_sizeof = strlen(path) + 1;
+
+	buf = Z_Malloc(buf_sizeof * sizeof(char));
+	Com_sprintf(buf, buf_sizeof, "%s", path);
+
+	for (start = buf; start != NULL && *start != '\0'; ) {
+		p = strchr(start, ':');
+		if (p != NULL) {
+			*p = '\0';
+		}
+
+		Com_sprintf(try_path, sizeof(try_path), "%s/%s", start, command);
+		if (access(try_path, F_OK | X_OK) == 0) {
+			flag = qtrue;
+			break;
+		}
+
+		if (p == NULL) {
+			break;
+		}
+		start = ++p;
+	}
+
+	Z_Free(buf);
+	return flag;
+}
+
+/*
+==================
 Sys_FreeFileList
 ==================
 */
@@ -557,9 +610,14 @@
 */
 static int Sys_ZenityCommand( dialogType_t type, const char *message, const char *title )	
 {
+	const char *cmd_name = "zenity";
 	const char *options = "";
 	char       command[ 1024 ];
 
+	if ( ! Sys_PathHasCommand(cmd_name)) {
+		return -1;
+	}
+
 	switch( type )
 	{
 		default:
@@ -570,8 +628,8 @@
 		case DT_OK_CANCEL: options = "--question --ok-label=\"OK\" --cancel-label=\"Cancel\""; break;
 	}
 
-	Com_sprintf( command, sizeof( command ), "zenity %s --text=\"%s\" --title=\"%s\"",
-		options, message, title );
+	Com_sprintf( command, sizeof( command ), "%s %s --text=\"%s\" --title=\"%s\"",
+		cmd_name, options, message, title );
 
 	return system( command );
 }
@@ -583,9 +641,14 @@
 */
 static int Sys_KdialogCommand( dialogType_t type, const char *message, const char *title )
 {
+	const char *cmd_name = "kdialog";
 	const char *options = "";
 	char       command[ 1024 ];
 
+	if ( ! Sys_PathHasCommand(cmd_name)) {
+		return -1;
+	}
+
 	switch( type )
 	{
 		default:
@@ -596,8 +659,8 @@
 		case DT_OK_CANCEL: options = "--warningcontinuecancel"; break;
 	}
 
-	Com_sprintf( command, sizeof( command ), "kdialog %s \"%s\" --title \"%s\"",
-		options, message, title );
+	Com_sprintf( command, sizeof( command ), "%s %s \"%s\" --title \"%s\"",
+		cmd_name, options, message, title );
 
 	return system( command );
 }
@@ -609,9 +672,14 @@
 */
 static int Sys_XmessageCommand( dialogType_t type, const char *message, const char *title )
 {
+	const char *cmd_name = "xmessage";
 	const char *options = "";
 	char       command[ 1024 ];
 
+	if ( ! Sys_PathHasCommand(cmd_name)) {
+		return -1;
+	}
+
 	switch( type )
 	{
 		default:           options = "-buttons OK"; break;
@@ -619,8 +687,8 @@
 		case DT_OK_CANCEL: options = "-buttons OK:0,Cancel:1"; break;
 	}
 
-	Com_sprintf( command, sizeof( command ), "xmessage -center %s \"%s\"",
-		options, message );
+	Com_sprintf( command, sizeof( command ), "%s -center %s \"%s\"",
+		cmd_name, options, message );
 
 	return system( command );
 }