curl basic auth using base64 encoded credentials

I was trying to access password-protected files via HTTPS using curl. The site required basic auth. For a demo, I created this example:
Username: admin
Password: 123456

It’s trivial to access this interactively via curl:

$ curl -u admin
Enter host password for user 'admin':

Or programmatically by providing the credentials in the URL:

$ curl

Or by providing a base64-encoded username:password pair in an Authorization header:

$ curl -H "Authorization: Basic $(echo -n admin:123456 | base64)"

(Note that echo includes a trailing newline character by default, which we do not want to include in the base64-encoded value. Specify the -n flag to echo to eliminate the trailing newline.)

But I was manipulating files with a Bash script that was being stored in a Git repository, and I didn’t want to store the credentials in the repository. So I stored the credentials in a separate file:

$ echo -n 'admin:123456' > ~/admin-credentials
$ chmod 0600 ~/admin-credentials

Now I can read the credentials from the file:

$ curl -H "Authorization: Basic $(cat admin-credentials | base64)"

I ran into a problem when I tried to update the credentials file with vi (or vim). Vi automatically inserts an end-of-line (EOL) character, which is not apparent to the user. The base64-encoded value includes the EOL character, and therefore the above command would supply invalid credentials.

To eliminate this in vi, use the following vi commands:

:set binary
:set noeol

Alternately, just overwrite the file with the updated credentials:

$ echo -n 'admin:123456' > ~/admin-credentials