1.1. help

$  etcdctl put --help
NAME:
        put - Puts the given key into the store

USAGE:
        etcdctl put [options] <key> <value> (<value> can also be given from stdin) [flags]

DESCRIPTION:
        Puts the given key into the store.

        When <value> begins with '-', <value> is interpreted as a flag.
        Insert '--' for workaround:

        $ put <key> -- <value>
        $ put -- <key> <value>

        If <value> isn't given as a command line argument and '--ignore-value' is not specified,
        this command tries to read the value from standard input.

        If <lease> isn't given as a command line argument and '--ignore-lease' is not specified,
        this command tries to read the value from standard input.

        For example,
        $ cat file | put <key>
        will store the content of the file to <key>.

OPTIONS:
  -h, --help[=false]            help for put
      --ignore-lease[=false]    updates the key using its current lease
      --ignore-value[=false]    updates the key using its current value
      --lease="0"               lease ID (in hexadecimal) to attach to the key
      --prev-kv[=false]         return the previous key-value pair before modification