updated usage() to make cli parsing flow more obvious

src/docsis.c

@@ -261,36 +261,38 @@ usage ()
   fprintf(stderr, "Copyright (c) 2002,2003,2004,2005 Evvolve Media SRL, docsis@evvolve.com\n");
   fprintf(stderr, "Copyright (c) 2014 - 2015 Adrian Simionov, daniel.simionov@gmail.com\n\n");
 
-  fprintf(stderr, "To encode a cable modem configuration file: \n\tdocsis -e <modem_cfg_file> <key_file> <output_file>\n");
-  fprintf(stderr, "To encode multiple cable modem configuration files: \n\tdocsis -m <modem_cfg_file1> ...  <key_file> <new_extension>\n");
-  fprintf(stderr, "To encode a MTA configuration file: \n\tdocsis -p <mta_cfg_file> <output_file>\n");
-  fprintf(stderr, "To encode multiple MTA configuration files: \n\tdocsis -m -p <mta_file1> ...  <new_extension>\n");
-  fprintf(stderr, "To decode a CM or MTA config file: \n\tdocsis -d <binary_file>\n");
-  fprintf(stderr, "To decode a CM or MTA config file with OIDs: \n\tdocsis -o -d <binary_file>\n");
-  fprintf(stderr, "\nTo specify the MIBPATH encode or decode use:\n"
-		  "\tdocsis -M \"PATH1:PATH2\" -d <binary_file>\n"
-		  "\tdocsis -M \"PATH1:PATH2\" -e <modem_cfg_file> <key_file> <output_file>\n"
-		  "\tdocsis -M \"PATH1:PATH2\" -m <modem_cfg_file1> ...  <key_file> <new_extension>\n"
-		  "\tdocsis -M \"PATH1:PATH2\" -p <mta_cfg_file> <output_file>\n"
-		  "\tdocsis -M \"PATH1:PATH2\" -m -p <mta_file1> ...  <new_extension>\n");
-  fprintf(stderr, "\nTo add SHA1 hash to mta config file, use -na or -eu options:\n");
-  fprintf(stderr, "\tdocsis -na|-eu -p <mta_cfg_file> <output_file>\n");
-  fprintf(stderr, "\tdocsis -na|-eu -m -p <mta_file1> ...  <new_extension>\n");
-  fprintf(stderr, "\nTo add PC20 dialplan from external dialplan.txt file, use -dialplan option:\n");
-  fprintf(stderr, "\tdocsis -p -dialplan <mta_cfg_file> <output_file>\n");
-  fprintf(stderr, "\tdocsis -na|-eu -p -dialplan <mta_cfg_file> <output_file>\n");
-  fprintf(stderr, "\nTo remove hash from MTA config file, use -nohash option:\n");
-  fprintf(stderr, "\tdocsis -nohash -d <mta_cfg_file>\n");
-  fprintf(stderr, "\tdocsis -nohash -o -d <mta_cfg_file>\n");
-  fprintf(stderr, "\nWhere:\n<cfg_file>\t\t= name of text (human readable) cable modem or MTA \n"
+  fprintf(stderr, "To encode a cable modem configuration file: \n\tdocsis [modifiers] -e <modem_cfg_file> <key_file> <output_file>\n");
+  fprintf(stderr, "To encode multiple cable modem configuration files: \n\tdocsis [modifiers] -m <modem_cfg_file1> ... <key_file> <new_extension>\n");
+  fprintf(stderr, "To encode a MTA configuration file: \n\tdocsis [modifiers] -p <mta_cfg_file> <output_file>\n");
+  fprintf(stderr, "To encode multiple MTA configuration files: \n\tdocsis [modifiers] -m -p <mta_file1> ... <new_extension>\n");
+  fprintf(stderr, "To decode a CM or MTA config file: \n\tdocsis [modifiers] -d <binary_file>\n\n");
+
+  fprintf(stderr, "Where:\n<cfg_file>\t\t= name of text (human readable) cable modem or MTA \n"
 		  "\t\t\t  configuration file;\n"
 		  "<key_file>\t\t= text file containing the authentication key\n"
 		  "\t\t\t  (shared secret) to be used for the CMTS MIC;\n"
 		  "<output_file> \t\t= name of output file where"
 		  " the binary data will\n\t\t\t  be written to (if it does not exist it is created);\n"
 		  "<binary_file>\t\t= name of binary file to be decoded;\n"
-		  "<new_extension>\t\t= new extension to be used when encoding multiple files.\n");
-  fprintf(stderr, "\nSee examples/*.cfg for configuration file format.\n");
+		  "<new_extension>\t\t= new extension to be used when encoding multiple files.\n\n");
+
+  fprintf(stderr, "The following command-line modifiers are available:\n"
+	"	-o\n"
+	"		Decode OIDs numerically.\n\n"
+	"	-M \"PATH1:PATH2\"\n"
+	"		Specify the SNMP MIB directory when encoding or decoding configuration\n"
+	"		files.\n\n"
+	"	-na | -eu\n"
+	"		Adds CableLabs PacketCable or Excentis EuroPacketCable SHA1 hash\n"
+	"		when encoding an MTA config file.\n\n"
+	"	-dialplan\n"
+	"		Adds a PC20 dialplan from an external file called \"dialplan.txt\" in\n"
+	"		the current directory.\n\n"
+	"	-nohash\n"
+	"		Removes the PacketCable SHA1 hash from the MTA config file when\n"
+	"		decoding.\n"
+	);
+  fprintf(stderr, "\nSee examples/*.cfg for sample configuration files.\n");
   fprintf(stderr, "\nPlease report bugs or feature requests on GitHub.");
   fprintf(stderr, "\nProject repository is https://github.com/rlaager/docsis\n\n");
   exit (-10);