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#include "command.hh"
#include "common-args.hh"
#include "shared.hh"
#include "store-api.hh"
#include "eval.hh"
#include "json.hh"
#include "value-to-json.hh"
using namespace nix;
struct CmdEval : MixJSON, InstallableCommand
{
bool raw = false;
CmdEval()
{
mkFlag(0, "raw", "print strings unquoted", &raw);
}
std::string name() override
{
return "eval";
}
std::string description() override
{
return "evaluate a Nix expression";
}
Examples examples() override
{
return {
Example{
"To evaluate a Nix expression given on the command line:",
"nix eval '(1 + 2)'"
},
Example{
"To evaluate a Nix expression from a file or URI:",
"nix eval -f channel:nixos-17.09 hello.name"
},
Example{
"To get the current version of Nixpkgs:",
"nix eval --raw nixpkgs.lib.nixpkgsVersion"
},
Example{
"To print the store path of the Hello package:",
"nix eval --raw nixpkgs.hello"
},
};
}
void run(ref<Store> store) override
{
if (raw && json)
throw UsageError("--raw and --json are mutually exclusive");
auto state = getEvalState();
auto v = installable->toValue(*state);
PathSet context;
if (raw) {
std::cout << state->coerceToString(noPos, *v, context);
} else if (json) {
JSONPlaceholder jsonOut(std::cout);
printValueAsJSON(*state, true, *v, jsonOut, context);
} else {
state->forceValueDeep(*v);
std::cout << *v << "\n";
}
}
};
static RegisterCommand r1(make_ref<CmdEval>());
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