Allow running fping --help even when raw socket can't be opened, fixes #131

CHANGELOG.md

@@ -5,6 +5,7 @@ fping 4.1 (UNRELEASED)
 
 - Fix problem when socket fd is 0 (#125, thanks Ramón Novoa!)
 - Fix running on servers with disabled IPv6 (#118, thanks Simon Matter)
+- Allow running "fping -h" or "--help" even when raw socket can't be opened (#131, thanks @teto)
 
 fping 4.0 (2017-04-23)
 ======================

src/fping.c

@@ -352,6 +352,12 @@ int main(int argc, char** argv)
     HOST_ENTRY* cursor;
     struct optparse optparse_state;
 
+    /* pre-parse -h/--help, so that we also can output help information
+     * without trying to open the socket, which might fail */
+    if(argc == 2 && ( strcmp(argv[1],"-h")==0 || strcmp(argv[1],"--help")==0 )) {
+        usage(0);
+    }
+
     socket4 = open_ping_socket_ipv4(ping_data_size);
 #ifdef IPV6
     socket6 = open_ping_socket_ipv6(ping_data_size);