openssl-passphrase-options - Pass phrase options
openssl command [ options ... ] [ parameters ... ]
Several OpenSSL commands accept password arguments, typically using
  -passin and -passout for input and output passwords
  respectively. These allow the password to be obtained from a variety of
  sources. Both of these options take a single argument whose format is
  described below. If no password argument is given and a password is required
  then the user is prompted to enter one: this will typically be read from the
  current terminal with echoing turned off.
Note that character encoding may be relevant, please see
    passphrase-encoding(7).
Pass phrase arguments can be formatted as follows.
  - pass:password
- The actual password is password. Since the password is visible to
      utilities (like 'ps' under Unix) this form should only be used where
      security is not important.
- env:var
- Obtain the password from the environment variable var. Since the
      environment of other processes is visible on certain platforms (e.g. ps
      under certain Unix OSes) this option should be used with caution.
- file:pathname
- The first line of pathname is the password. If the same
      pathname argument is supplied to -passin and -passout
      arguments then the first line will be used for the input password and the
      next line for the output password. pathname need not refer to a
      regular file: it could for example refer to a device or named pipe.
- fd:number
- Read the password from the file descriptor number. This can be used
      to send the data via a pipe for example.
- stdin
- Read the password from standard input.
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    You may not use this file except in compliance with the License. You can
    obtain a copy in the file LICENSE in the source distribution or at
    <https://www.openssl.org/source/license.html>.