The only dependencies are cat, date and openssl.

You are recommended to use it with pass from https://www.passwordstore.org/

For example, to get the token for two-factor authentication:

# Usage: totp [server] [interval] [timestamp] < secret
pass show otp/GitHub | totp GitHub

# Run this at Fri Jan 1 00:00:00 UTC 2038 you'd get 846121.
printf "%s" "base32-decoded secret" | base32 | totp GitHub 30 #2145916800

In the first example above, the second parameter "GitHub" is optional, and defaults to "Google", since the Google Authenticator app has become the de facto standard for such usage.

License:

• totp : at the top of the source code (WTF)

• totp.py : at the top of the source code (MIT)

• other :

  This is free and unencumbered software released into the public domain.
  
  Anyone is free to copy, modify, publish, use, compile, sell, or
  distribute this software, either in source code form or as a compiled
  binary, for any purpose, commercial or non-commercial, and by any
  means.
  
  In jurisdictions that recognize copyright laws, the author or authors
  of this software dedicate any and all copyright interest in the
  software to the public domain. We make this dedication for the benefit
  of the public at large and to the detriment of our heirs and
  successors. We intend this dedication to be an overt act of
  relinquishment in perpetuity of all present and future rights to this
  software under copyright law.
  
  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
  IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
  OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
  ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  OTHER DEALINGS IN THE SOFTWARE.
  
  For more information, please refer to https://unlicense.org/