gnupg: Invoking gpg-preset-passphrase
9.6.1 List of all commands and options
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'gpg-preset-passphrase' is invoked this way:
gpg-preset-passphrase [options] [command] CACHEID
CACHEID is either a 40 character keygrip of hexadecimal characters
identifying the key for which the passphrase should be set or cleared.
The keygrip is listed along with the key when running the command:
'gpgsm --with-keygrip --list-secret-keys'. Alternatively an arbitrary
string may be used to identify a passphrase; it is suggested that such a
string is prefixed with the name of the application (e.g 'foo:12346').
Scripts should always use the option '--with-colons', which provides the
keygrip in a "grp" line (cf. 'doc/DETAILS')/
One of the following command options must be given:
'--preset'
Preset a passphrase. This is what you usually will use.
'gpg-preset-passphrase' will then read the passphrase from 'stdin'.
'--forget'
Flush the passphrase for the given cache ID from the cache.
The following additional options may be used:
'-v'
'--verbose'
Output additional information while running.
'-P STRING'
'--passphrase STRING'
Instead of reading the passphrase from 'stdin', use the supplied
STRING as passphrase. Note that this makes the passphrase visible
for other users.