Read the derivation from PATH (`/gnu/store/xxx.drv'), and return the store path of its output OUTPUT.

Return the output file name of INPUT. If INPUT has more than one outputs, an error is raised.

Return #t if DRV can be substituted.

Return the list of output paths corresponding to INPUT, a <derivation-input>.

Return #t if DRV is a fixed-output derivation, such as the result of a download with a fixed hash (aka. `fetchurl').

Return true if INPUT is valid--i.e., if all the outputs it requests are in the store.

Write the ATerm-like serialization of DRV to PORT. See Section 2.4 of Eelco Dolstra's PhD dissertation for an overview of a previous version of that form.

Invalidate internal derivation caches. This is mostly useful for long-running processes that know what they're doing. Use with care!

Build a derivation with the given arguments, and return the resulting <derivation> object. When HASH and HASH-ALGO are given, a fixed-output derivation is created---i.e., one whose result is known in advance, such as a file download. If, in addition, RECURSIVE? is true, then that fixed output may be an executable file or a directory and HASH must be the hash of an archive containing this output.

When REFERENCES-GRAPHS is true, it must be a list of file name/store path pairs. In that case, the reference graph of each store path is exported in the build environment in the corresponding file, in a simple text format.

When ALLOWED-REFERENCES is true, it must be a list of store items or outputs that the derivation's outputs may refer to. Likewise, DISALLOWED-REFERENCES, if true, must be a list of things the outputs may not refer to.

When LEAKED-ENV-VARS is true, it must be a list of strings denoting environment variables that are allowed to "leak" from the daemon's environment to the build environment. This is only applicable to fixed-output derivations--i.e., when HASH is true. The main use is to allow variables such as "http_proxy" to be passed to derivations that download files.

When LOCAL-BUILD? is true, declare that the derivation is not a good candidate for offloading and should rather be built locally. This is the case for small derivations where the costs of data transfers would outweigh the benefits.

When SUBSTITUTABLE? is false, declare that substitutes of the derivation's output should not be used.

PROPERTIES must be an association list describing "properties" of the derivation. It is kept as-is, uninterpreted, in the derivation.

Return the list of derivation-inputs required to build DRV, recursively.

CUT? is a predicate that is passed a derivation-input and returns true to eliminate the given input and its dependencies from the search. An example of such a predicate is 'valid-derivation-input?'; when it is used as CUT?, the result is the set of prerequisites of DRV not already in valid.

Return the store path of its output OUTPUT. Raise a '&derivation-missing-output-error' condition if OUTPUT is not an output of DRV.