do nothing but print keep alive characters, can be used for login shell

This is a minimal program that does nothing but print some characters (namely version information and time&date string) every now and then. It is intended to be used for login shell with accounts accessible via secure shell that are used for secure tunneling but should not allow to execute commands.


To compile and run nullshell you need:

  • nothing (this is plain C)
  • markdown (HTML documentation)

Additionally it is expected to have make and a C compiler around to successfully compile.

Build and install

Building and installing is very easy. Just run:


followed by:

make install

This will place an executable at /usr/bin/nullshell.


To create a new user user with nullshell as login shell just run:

useradd -s /usr/bin/nullshell user

Or to make nullshell the login shell for an existing user user:

usermod -s /usr/bin/nullshell user

Make sure /usr/bin/nullshell is listed in /etc/shells if your system expects this.

License and warranty

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.


URL: GitHub.com

Mirror: eworm.de GitLab.com