Prince Networking

Prince can process local files or fetch them from remote locations. To do this, a full URL needs to be provided, including the protocol.

    $ prince http://example.com/path/file.html -o out.pdf

Authentication

If authentication is required for the URL, the credentials can be passed by means of the --auth-user and --auth-password command-line options. A more cautious way is to add the --auth-server option, which sends username and password credentials to the specified server only - the default is to send them to any server which challenges for authentication. The option --auth-scheme sends username and password credentials only for requests with the given scheme, either HTTP or HTTPS, while --auth-method specifies a comma separated list of HTTP authentication methods to enable. Valid entries are: basic, digest, ntlm and negotiate.

A shorthand command-line option for authentication is --auth, which specifies a URL with credentials for HTTP authentication: [SCHEME:]//USER:PASS@HOST[:PORT]. Unlike the preceding options, it may be used multiple times. The username and password must be percent-encoded.

The advanced command-line option --no-auth-preemptive instructs Prince not to send credentials to named servers until an authentication challenge is received. When multiple authentication methods are enabled, an initial request may be required to discover the methods supported by the remote site.

Cookies

If cookies are required, the --cookie command-line option can be used to set a value for the Set-Cookie HTTP header value. If you do not specify a domain for the cookie, it may not be sent. The exact behaviour depends on the underlying libcurl version. The option may be used multiple times. Alternatively, the option --cookie-file specifies a file containing HTTP cookies.

SSL

The command-line option --ssl-cacert specifies an SSL certificate file, while the option --ssl-capath is used to specify an SSL certificate directory.

The command-line option --ssl-version sets the minimum version of SSL to allow. It may be one of: default, tlsv1, tlsv1.0, tlsv1.1, tlsv1.2 or tlsv1.3. The value default lets libcurl choose.

Prince on Windows allows for fine-tuning SSL certificate revocation checks: by default Prince ignores certificate revocation checks that fail due to missing or offline distribution points for the revocation check lists, but this behaviour can be disabled with --no-ssl-revoke-best-effort. Alternatively, it can outright disable certificate revocation checks with --ssl-no-revoke.

The option --insecure disables SSL verification altogether. Please note that using this option is not recommended! As the name already suggests, all secure connections are downgraded to insecure.

Prince makes use of the libcurl library to process network locations - see Acknowledgments. Please note that command-line options are passed to curl as-is. On some systems curl might use a library other than OpenSSL to handle SSL - in those cases the SSL-related command-line options might behave in a slightly different way. In case of doubt, please check your own curl documentation.

Client Certificates

Client certificates are supported on Linux with several command-line options. The --ssl-cert option specifies an SSL client certificate file, while the --ssl-cert-type option defines the SSL client certificate file type (PEM, DER) - the default is PEM. The option --ssl-key specifies an SSL private key file and --ssl-key-type is used to define the SSL private key file type (PEM, DER) - the default is PEM. Last but not least, --ssl-key-password indicates the passphrase for the private key.

On MacOS, the command-line option --ssl-cert specifies a PKCS#12 file containing a client certificate and private key. The options --ssl-cert-type, --ssl-key and --ssl-key-password are not available.

Client certificates are not supported on Windows.

Miscellaneous

If an HTTP proxy server is required, it can be specified with the --http-proxy command-line option.

Please note that since Prince uses curl for loading resources from HTTP URLs, it is possible to use curl-supported environment variables (such as e.g. http_proxy and no_proxy) to fine-tune the proxy rules. In this case it is not necessary to specify the command-line option - the proxy rules are provided through the environment variables. See this forum post for more details.

The option --http-timeout can be used to define the HTTP timeout in seconds, which can be useful for slow servers.

Prince can also disable downloading multiple HTTP resources at once with the --no-parallel-downloads command-line option.

Custom HTTP headers

In extreme cases, a custom user-agent string can be passed to Prince with the --user-agent command-line option in order to circumvent user-agent-sniffing that leads to undesired results, degrading the PDF output.

Other custom HTTP headers can be sent to the server with the command-line option --http-header. To send multiple custom headers, use the option multiple times. Note that headers already sent by Prince can be overridden by this command-line option, but cannot be removed.

Please be aware that there can be unforseen side-effects when manipulating HTTP headers, including the User-Agent header.