The modes parameter specifies what kind of operaion the encoding should be generated for. There are three valid modes:
.SS tx
Generates a transaction that changes state. Used with \fB--format\fP \fIrpc\fP it will generate an \fIeth_sendRawTransaction\fP jsonrpc object. Used with \fB--format\fP \fIbin\fP it outputs signed RLP only in hexdecimal.
.SS call
Generates a query that reads state. Used with \fB--format\fP \fIrpc\fP it will generate a \fIeth_call\fP jsonrpc object with applicable fields filled out from environment, arguments and/or rpc retrieval. \fB--format\fP \fIbin\fP is not valid for this mode.
.SS arg
Encodes the argument part only, optionally with a method signature. \fB--format\fP \fIrpc\fP is not valid for this mode.
