This program provides a straightforward command-line interface to crypt(3).

sudo apt install libssl-dev
./autogen.sh
./configure
make check
sudo make install

$ crypt3 
Enter password: 
Retype password: 
$6$DLwtdvJ.mGpVjtsd$6NKZLh/WIi9Gd2vvnYrzJ7bDCrOA2lTMasIdrzy9V//BsRDL9yC2RIxJan5eaExJkWUKleh125B22FN64PELs0

crypt3 --help
man crypt3

crypt3 will let you specify passwords on the command line. This isn't very secure since command line are visible in ps, but it's convenient for low-value passwords.

crypt3 makes no effort to evaluate password strength.

crypt3 will let you use obsolete modes of crypt(3), even though they are totally insecure. Only use them if you're stuck with an ancient application which cannot do better.

crypt3 exists to interwork with applications that are already committed to crypt(3). If you're creating a new system and need to protect passwords, consult Cryptographic Right Answers.

Copyright © Richard Kettewell.

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see www.gnu.org/licenses.

crypt3 embeds its own copy of the password-hashing code, in order to be independent of platform C libraries (which don't all support the same algorithms). The code used was taken from FreeBSD.

Variously copyright © Dag-Erling Smørgrav, David Burren, Mark Murray, Poul-Henning Kamp, Richard Kettlewell, The FreeBSD Project, University of California.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
3. Neither the name of the author nor the names of other contributors may be used to endorse or promote products derived from this software without specific prior written permission.