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3.1.2 Commands to select the type of operation

--sign
-s
Make a signature. This command may be combined with --encrypt (for a signed and encrypted message), --symmetric (for a signed and symmetrically encrypted message), or --encrypt and --symmetric together (for a signed message that may be decrypted via a secret key or a passphrase). The key to be used for signing is chosen by default or can be set with the --local-user and --default-key options.
--clearsign
Make a clear text signature. The content in a clear text signature is readable without any special software. OpenPGP software is only needed to verify the signature. Clear text signatures may modify end-of-line whitespace for platform independence and are not intended to be reversible. The key to be used for signing is chosen by default or can be set with the --local-user and --default-key options.
--detach-sign
-b
Make a detached signature.
--encrypt
-e
Encrypt data. This option may be combined with --sign (for a signed and encrypted message), --symmetric (for a message that may be decrypted via a secret key or a passphrase), or --sign and --symmetric together (for a signed message that may be decrypted via a secret key or a passphrase).
--symmetric
-c
Encrypt with a symmetric cipher using a passphrase. The default symmetric cipher used is CAST5, but may be chosen with the --cipher-algo option. This option may be combined with --sign (for a signed and symmetrically encrypted message), --encrypt (for a message that may be decrypted via a secret key or a passphrase), or --sign and --encrypt together (for a signed message that may be decrypted via a secret key or a passphrase).
--store
Store only (make a simple RFC1991 literal data packet).
--decrypt
-d
Decrypt the file given on the command line (or STDIN if no file is specified) and write it to STDOUT (or the file specified with --output). If the decrypted file is signed, the signature is also verified. This command differs from the default operation, as it never writes to the filename which is included in the file and it rejects files which don't begin with an encrypted message.
--verify
Assume that the first argument is a signed file or a detached signature and verify it without generating any output. With no arguments, the signature packet is read from STDIN. If only a sigfile is given, it may be a complete signature or a detached signature, in which case the signed stuff is expected in a file without the ".sig" or ".asc" extension. With more than 1 argument, the first should be a detached signature and the remaining files are the signed stuff. To read the signed stuff from STDIN, use ‘-’ as the second filename. For security reasons a detached signature cannot read the signed material from STDIN without denoting it in the above way.

Note: When verifying a cleartext signature, gpg verifies only what makes up the cleartext signed data and not any extra data outside of the cleartext signature or header lines following directly the dash marker line. The option --output may be used to write out the actual signed data; but there are other pitfalls with this format as well. It is suggested to avoid cleartext signatures in favor of detached signatures.

--multifile
This modifies certain other commands to accept multiple files for processing on the command line or read from STDIN with each filename on a separate line. This allows for many files to be processed at once. --multifile may currently be used along with --verify, --encrypt, and --decrypt. Note that --multifile --verify may not be used with detached signatures.
--verify-files
Identical to --multifile --verify.
--encrypt-files
Identical to --multifile --encrypt.
--decrypt-files
Identical to --multifile --decrypt.
--list-keys
-k
--list-public-keys
List all keys from the public keyrings, or just the keys given on the command line.

Avoid using the output of this command in scripts or other programs as it is likely to change as GnuPG changes. See --with-colons for a machine-parseable key listing command that is appropriate for use in scripts and other programs.

--list-secret-keys
-K
List all keys from the secret keyrings, or just the ones given on the command line. A # after the letters sec means that the secret key is not usable (for example, if it was created via --export-secret-subkeys).
--list-sigs
Same as --list-keys, but the signatures are listed too. This command has the same effect as using --list-keys with --with-sig-list.

For each signature listed, there are several flags in between the "sig" tag and keyid. These flags give additional information about each signature. From left to right, they are the numbers 1-3 for certificate check level (see --ask-cert-level), "L" for a local or non-exportable signature (see --lsign-key), "R" for a nonRevocable signature (see the --edit-key command "nrsign"), "P" for a signature that contains a policy URL (see --cert-policy-url), "N" for a signature that contains a notation (see --cert-notation), "X" for an eXpired signature (see --ask-cert-expire), and the numbers 1-9 or "T" for 10 and above to indicate trust signature levels (see the --edit-key command "tsign").

--check-sigs
Same as --list-sigs, but the signatures are verified. Note that for performance reasons the revocation status of a signing key is not shown. This command has the same effect as using --list-keys with --with-sig-check.

The status of the verification is indicated by a flag directly following the "sig" tag (and thus before the flags described above for --list-sigs). A "!" indicates that the signature has been successfully verified, a "-" denotes a bad signature and a "%" is used if an error occurred while checking the signature (e.g. a non supported algorithm).

--locate-keys
Locate the keys given as arguments. This command basically uses the same algorithm as used when locating keys for encryption or signing and may thus be used to see what keys gpg2 might use. In particular external methods as defined by --auto-key-locate may be used to locate a key. Only public keys are listed.
--fingerprint
List all keys (or the specified ones) along with their fingerprints. This is the same output as --list-keys but with the additional output of a line with the fingerprint. May also be combined with --list-sigs or --check-sigs. If this command is given twice, the fingerprints of all secondary keys are listed too.
--list-packets
List only the sequence of packets. This is mainly useful for debugging.
--card-edit
Present a menu to work with a smartcard. The subcommand "help" provides an overview on available commands. For a detailed description, please see the Card HOWTO at http://www.gnupg.org/documentation/howtos.html#GnuPG-cardHOWTO .
--card-status
Show the content of the smart card.
--change-pin
Present a menu to allow changing the PIN of a smartcard. This functionality is also available as the subcommand "passwd" with the --card-edit command.
--delete-key name
Remove key from the public keyring. In batch mode either --yes is required or the key must be specified by fingerprint. This is a safeguard against accidental deletion of multiple keys.
--delete-secret-key name
Remove key from the secret keyring. In batch mode the key must be specified by fingerprint.
--delete-secret-and-public-key name
Same as --delete-key, but if a secret key exists, it will be removed first. In batch mode the key must be specified by fingerprint.
--export
Either export all keys from all keyrings (default keyrings and those registered via option --keyring), or if at least one name is given, those of the given name. The new keyring is written to STDOUT or to the file given with option --output. Use together with --armor to mail those keys.
--send-keys key IDs
Similar to --export but sends the keys to a keyserver. Fingerprints may be used instead of key IDs. Option --keyserver must be used to give the name of this keyserver. Don't send your complete keyring to a keyserver — select only those keys which are new or changed by you. If no key IDs are given, gpg does nothing.
--export-secret-keys
--export-secret-subkeys
Same as --export, but exports the secret keys instead. This is normally not very useful and a security risk. The second form of the command has the special property to render the secret part of the primary key useless; this is a GNU extension to OpenPGP and other implementations can not be expected to successfully import such a key. See the option --simple-sk-checksum if you want to import such an exported key with an older OpenPGP implementation.
--import
--fast-import
Import/merge keys. This adds the given keys to the keyring. The fast version is currently just a synonym.

There are a few other options which control how this command works. Most notable here is the --import-options merge-only option which does not insert new keys but does only the merging of new signatures, user-IDs and subkeys.

--recv-keys key IDs
Import the keys with the given key IDs from a keyserver. Option --keyserver must be used to give the name of this keyserver.
--refresh-keys
Request updates from a keyserver for keys that already exist on the local keyring. This is useful for updating a key with the latest signatures, user IDs, etc. Calling this with no arguments will refresh the entire keyring. Option --keyserver must be used to give the name of the keyserver for all keys that do not have preferred keyservers set (see --keyserver-options honor-keyserver-url).
--search-keys names
Search the keyserver for the given names. Multiple names given here will be joined together to create the search string for the keyserver. Option --keyserver must be used to give the name of this keyserver. Keyservers that support different search methods allow using the syntax specified in "How to specify a user ID" below. Note that different keyserver types support different search methods. Currently only LDAP supports them all.
--fetch-keys URIs
Retrieve keys located at the specified URIs. Note that different installations of GnuPG may support different protocols (HTTP, FTP, LDAP, etc.)
--update-trustdb
Do trust database maintenance. This command iterates over all keys and builds the Web of Trust. This is an interactive command because it may have to ask for the "ownertrust" values for keys. The user has to give an estimation of how far she trusts the owner of the displayed key to correctly certify (sign) other keys. GnuPG only asks for the ownertrust value if it has not yet been assigned to a key. Using the --edit-key menu, the assigned value can be changed at any time.
--check-trustdb
Do trust database maintenance without user interaction. From time to time the trust database must be updated so that expired keys or signatures and the resulting changes in the Web of Trust can be tracked. Normally, GnuPG will calculate when this is required and do it automatically unless --no-auto-check-trustdb is set. This command can be used to force a trust database check at any time. The processing is identical to that of --update-trustdb but it skips keys with a not yet defined "ownertrust".

For use with cron jobs, this command can be used together with --batch in which case the trust database check is done only if a check is needed. To force a run even in batch mode add the option --yes.


--export-ownertrust
Send the ownertrust values to STDOUT. This is useful for backup purposes as these values are the only ones which can't be re-created from a corrupted trustdb. Example:
            gpg2 --export-ownertrust > otrust.txt

--import-ownertrust
Update the trustdb with the ownertrust values stored in files (or STDIN if not given); existing values will be overwritten. In case of a severely damaged trustdb and if you have a recent backup of the ownertrust values (e.g. in the file otrust.txt, you may re-create the trustdb using these commands:
            cd ~/.gnupg
            rm trustdb.gpg
            gpg2 --import-ownertrust < otrust.txt

--rebuild-keydb-caches
When updating from version 1.0.6 to 1.0.7 this command should be used to create signature caches in the keyring. It might be handy in other situations too.
--print-md algo
--print-mds
Print message digest of algorithm ALGO for all given files or STDIN. With the second form (or a deprecated "*" as algo) digests for all available algorithms are printed.
--gen-random 0|1|2 count
Emit count random bytes of the given quality level 0, 1 or 2. If count is not given or zero, an endless sequence of random bytes will be emitted. If used with --armor the output will be base64 encoded. PLEASE, don't use this command unless you know what you are doing; it may remove precious entropy from the system!
--gen-prime mode bits
Use the source, Luke :-). The output format is still subject to change.
--enarmor
--dearmor
Pack or unpack an arbitrary input into/from an OpenPGP ASCII armor. This is a GnuPG extension to OpenPGP and in general not very useful.