help语法

ssh-keygen

➜  iOS_Tweak which ssh-keygen
/usr/bin/ssh-keygen
➜  iOS_Tweak ssh-keygen --version
ssh-keygen: illegal option -- -
usage: ssh-keygen [-q] [-b bits] [-C comment] [-f output_keyfile] [-m format]
                  [-N new_passphrase] [-t dsa | ecdsa | ed25519 | rsa]
       ssh-keygen -p [-f keyfile] [-m format] [-N new_passphrase]
                   [-P old_passphrase]
       ssh-keygen -i [-f input_keyfile] [-m key_format]
       ssh-keygen -e [-f input_keyfile] [-m key_format]
       ssh-keygen -y [-f input_keyfile]
       ssh-keygen -c [-C comment] [-f keyfile] [-P passphrase]
       ssh-keygen -l [-v] [-E fingerprint_hash] [-f input_keyfile]
       ssh-keygen -B [-f input_keyfile]
       ssh-keygen -D pkcs11
       ssh-keygen -F hostname [-lv] [-f known_hosts_file]
       ssh-keygen -H [-f known_hosts_file]
       ssh-keygen -R hostname [-f known_hosts_file]
       ssh-keygen -r hostname [-g] [-f input_keyfile]
       ssh-keygen -G output_file [-v] [-b bits] [-M memory] [-S start_point]
       ssh-keygen -f input_file -T output_file [-v] [-a rounds] [-J num_lines]
                  [-j start_line] [-K checkpt] [-W generator]
       ssh-keygen -I certificate_identity -s ca_key [-hU] [-D pkcs11_provider]
                  [-n principals] [-O option] [-V validity_interval]
                  [-z serial_number] file ...
       ssh-keygen -L [-f input_keyfile]
       ssh-keygen -A [-f prefix_path]
       ssh-keygen -k -f krl_file [-u] [-s ca_public] [-z version_number]
                  file ...
       ssh-keygen -Q -f krl_file file ...
       ssh-keygen -Y check-novalidate -n namespace -s signature_file
       ssh-keygen -Y sign -f key_file -n namespace file ...
       ssh-keygen -Y verify -f allowed_signers_file -I signer_identity
               -n namespace -s signature_file [-r revocation_file]

ssh-copy-id

➜  iOS_Tweak which ssh-copy-id
/usr/bin/ssh-copy-id
➜  iOS_Tweak ssh-copy-id --version


/usr/bin/ssh-copy-id: ERROR: invalid option (--version)


Usage: /usr/bin/ssh-copy-id [-h|-?|-f|-n] [-i [identity_file]] [-p port] [[-o <ssh -o options>] ...] [user@]hostname
    -f: force mode -- copy keys without trying to check if they are already installed
    -n: dry run    -- no keys are actually copied
    -h|-?: print this help