lix/src/nix/shell.cc

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#include "eval.hh"
#include "command.hh"
#include "common-args.hh"
#include "shared.hh"
#include "store-api.hh"
#include "derivations.hh"
#include "affinity.hh"
#include "progress-bar.hh"
#include <regex>
using namespace nix;
struct Var
{
bool exported = true;
bool associative = false;
std::string value; // quoted string or array
};
struct BuildEnvironment
{
std::map<std::string, Var> env;
std::string bashFunctions;
};
BuildEnvironment readEnvironment(const Path & path)
{
BuildEnvironment res;
std::set<std::string> exported;
debug("reading environment file '%s'", path);
auto file = readFile(path);
auto pos = file.cbegin();
static std::string varNameRegex =
R"re((?:[a-zA-Z_][a-zA-Z0-9_]*))re";
static std::regex declareRegex(
"^declare -x (" + varNameRegex + ")" +
R"re((?:="((?:[^"\\]|\\.)*)")?\n)re");
static std::string simpleStringRegex =
R"re((?:[a-zA-Z0-9_/:\.\-\+=]*))re";
static std::string quotedStringRegex =
R"re((?:\$?'(?:[^'\\]|\\[abeEfnrtv\\'"?])*'))re";
static std::string indexedArrayRegex =
R"re((?:\(( *\[[0-9]+]="(?:[^"\\]|\\.)*")**\)))re";
static std::regex varRegex(
"^(" + varNameRegex + ")=(" + simpleStringRegex + "|" + quotedStringRegex + "|" + indexedArrayRegex + ")\n");
/* Note: we distinguish between an indexed and associative array
using the space before the closing parenthesis. Will
undoubtedly regret this some day. */
static std::regex assocArrayRegex(
"^(" + varNameRegex + ")=" + R"re((?:\(( *\[[^\]]+\]="(?:[^"\\]|\\.)*")* *\)))re" + "\n");
static std::regex functionRegex(
"^" + varNameRegex + " \\(\\) *\n");
while (pos != file.end()) {
std::smatch match;
if (std::regex_search(pos, file.cend(), match, declareRegex)) {
pos = match[0].second;
exported.insert(match[1]);
}
else if (std::regex_search(pos, file.cend(), match, varRegex)) {
pos = match[0].second;
res.env.insert({match[1], Var { .exported = exported.count(match[1]) > 0, .value = match[2] }});
}
else if (std::regex_search(pos, file.cend(), match, assocArrayRegex)) {
pos = match[0].second;
res.env.insert({match[1], Var { .associative = true, .value = match[2] }});
}
else if (std::regex_search(pos, file.cend(), match, functionRegex)) {
res.bashFunctions = std::string(pos, file.cend());
break;
}
else throw Error("shell environment '%s' has unexpected line '%s'",
path, file.substr(pos - file.cbegin(), 60));
}
return res;
}
const static std::string getEnvSh =
#include "get-env.sh.gen.hh"
;
/* Given an existing derivation, return the shell environment as
initialised by stdenv's setup script. We do this by building a
modified derivation with the same dependencies and nearly the same
initial environment variables, that just writes the resulting
environment to a file and exits. */
StorePath getDerivationEnvironment(ref<Store> store, const StorePath & drvPath)
{
auto drv = store->derivationFromPath(drvPath);
auto builder = baseNameOf(drv.builder);
if (builder != "bash")
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throw Error("'nix dev-shell' only works on derivations that use 'bash' as their builder");
auto getEnvShPath = store->addTextToStore("get-env.sh", getEnvSh, {});
drv.args = {store->printStorePath(getEnvShPath)};
/* Remove derivation checks. */
drv.env.erase("allowedReferences");
drv.env.erase("allowedRequisites");
drv.env.erase("disallowedReferences");
drv.env.erase("disallowedRequisites");
/* Rehash and write the derivation. FIXME: would be nice to use
'buildDerivation', but that's privileged. */
auto drvName = std::string(drvPath.name());
assert(hasSuffix(drvName, ".drv"));
drvName.resize(drvName.size() - 4);
drvName += "-env";
for (auto & output : drv.outputs)
drv.env.erase(output.first);
drv.env["out"] = "";
drv.env["outputs"] = "out";
drv.inputSrcs.insert(std::move(getEnvShPath));
Hash h = hashDerivationModulo(*store, drv, true);
auto shellOutPath = store->makeOutputPath("out", h, drvName);
drv.outputs.insert_or_assign("out", DerivationOutput(shellOutPath.clone(), "", ""));
drv.env["out"] = store->printStorePath(shellOutPath);
auto shellDrvPath2 = writeDerivation(store, drv, drvName);
/* Build the derivation. */
store->buildPaths({shellDrvPath2});
assert(store->isValidPath(shellOutPath));
return shellOutPath;
}
struct Common : InstallableCommand, MixProfile
{
std::set<string> ignoreVars{
"BASHOPTS",
"EUID",
"HOME", // FIXME: don't ignore in pure mode?
"NIX_BUILD_TOP",
"NIX_ENFORCE_PURITY",
"NIX_LOG_FD",
"PPID",
"PWD",
"SHELLOPTS",
"SHLVL",
"SSL_CERT_FILE", // FIXME: only want to ignore /no-cert-file.crt
"TEMP",
"TEMPDIR",
"TERM",
"TMP",
"TMPDIR",
"TZ",
"UID",
};
void makeRcScript(const BuildEnvironment & buildEnvironment, std::ostream & out)
{
out << "nix_saved_PATH=\"$PATH\"\n";
for (auto & i : buildEnvironment.env) {
if (!ignoreVars.count(i.first) && !hasPrefix(i.first, "BASH_")) {
if (i.second.associative)
out << fmt("declare -A %s=(%s)\n", i.first, i.second.value);
else {
out << fmt("%s=%s\n", i.first, i.second.value);
if (i.second.exported)
out << fmt("export %s\n", i.first);
}
}
}
out << "PATH=\"$PATH:$nix_saved_PATH\"\n";
out << buildEnvironment.bashFunctions << "\n";
// FIXME: set outputs
out << "export NIX_BUILD_TOP=\"$(mktemp -d --tmpdir nix-shell.XXXXXX)\"\n";
for (auto & i : {"TMP", "TMPDIR", "TEMP", "TEMPDIR"})
out << fmt("export %s=\"$NIX_BUILD_TOP\"\n", i);
out << "eval \"$shellHook\"\n";
}
StorePath getShellOutPath(ref<Store> store)
{
auto path = installable->getStorePath();
if (path && hasSuffix(path->to_string(), "-env"))
return path->clone();
else {
auto drvs = toDerivations(store, {installable});
if (drvs.size() != 1)
throw Error("'%s' needs to evaluate to a single derivation, but it evaluated to %d derivations",
installable->what(), drvs.size());
auto & drvPath = *drvs.begin();
return getDerivationEnvironment(store, drvPath);
}
}
std::pair<BuildEnvironment, std::string> getBuildEnvironment(ref<Store> store)
{
auto shellOutPath = getShellOutPath(store);
auto strPath = store->printStorePath(shellOutPath);
updateProfile(shellOutPath);
return {readEnvironment(strPath), strPath};
}
};
struct CmdDevShell : Common, MixEnvironment
{
std::vector<std::string> command;
CmdDevShell()
{
mkFlag()
.longName("command")
.shortName('c')
.description("command and arguments to be executed insted of an interactive shell")
.labels({"command", "args"})
.arity(ArityAny)
.handler([&](std::vector<std::string> ss) {
if (ss.empty()) throw UsageError("--command requires at least one argument");
command = ss;
});
}
std::string description() override
{
return "run a bash shell that provides the build environment of a derivation";
}
Examples examples() override
{
return {
Example{
"To get the build environment of GNU hello:",
"nix dev-shell nixpkgs.hello"
},
Example{
"To store the build environment in a profile:",
"nix dev-shell --profile /tmp/my-shell nixpkgs.hello"
},
Example{
"To use a build environment previously recorded in a profile:",
"nix dev-shell /tmp/my-shell"
},
};
}
void run(ref<Store> store) override
{
auto [buildEnvironment, gcroot] = getBuildEnvironment(store);
auto [rcFileFd, rcFilePath] = createTempFile("nix-shell");
std::ostringstream ss;
makeRcScript(buildEnvironment, ss);
ss << fmt("rm -f '%s'\n", rcFilePath);
if (!command.empty()) {
std::vector<std::string> args;
for (auto s : command)
args.push_back(shellEscape(s));
ss << fmt("exec %s\n", concatStringsSep(" ", args));
}
writeFull(rcFileFd.get(), ss.str());
stopProgressBar();
auto shell = getEnv("SHELL").value_or("bash");
setEnviron();
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// prevent garbage collection until shell exits
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setenv("NIX_GCROOT", gcroot.data(), 1);
auto args = Strings{std::string(baseNameOf(shell)), "--rcfile", rcFilePath};
restoreAffinity();
restoreSignals();
execvp(shell.c_str(), stringsToCharPtrs(args).data());
throw SysError("executing shell '%s'", shell);
}
};
struct CmdPrintDevEnv : Common
{
std::string description() override
{
return "print shell code that can be sourced by bash to reproduce the build environment of a derivation";
}
Examples examples() override
{
return {
Example{
"To apply the build environment of GNU hello to the current shell:",
". <(nix print-dev-env nixpkgs.hello)"
},
};
}
void run(ref<Store> store) override
{
auto buildEnvironment = getBuildEnvironment(store).first;
stopProgressBar();
makeRcScript(buildEnvironment, std::cout);
}
};
static auto r1 = registerCommand<CmdPrintDevEnv>("print-dev-env");
static auto r2 = registerCommand<CmdDevShell>("dev-shell");