Merge changes from topic "libutil-split" into main

* changes:
  util.hh: Delete remaining file and clean up headers
  util.hh: Move nativeSystem to local-derivation-goal.cc
  util.hh: Move stuff to types.hh
  util.cc: Delete remaining file
  util.{hh,cc}: Move ignoreException to error.{hh,cc}
  util.{hh,cc}: Split out namespaces.{hh,cc}
  util.{hh,cc}: Split out users.{hh,cc}
  util.{hh,cc}: Split out strings.{hh,cc}
  util.{hh,cc}: Split out unix-domain-socket.{hh,cc}
  util.{hh,cc}: Split out child.{hh,cc}
  util.{hh,cc}: Split out current-process.{hh,cc}
  util.{hh,cc}: Split out processes.{hh,cc}
  util.{hh,cc}: Split out file-descriptor.{hh,cc}
  util.{hh,cc}: Split out file-system.{hh,cc}
  util.{hh,cc}: Split out terminal.{hh,cc}
  util.{hh,cc}: Split out environment-variables.{hh,cc}

1 files changed, 51 insertions, 0 deletions

diff --git a/src/libutil/environment-variables.cc b/src/libutil/environment-variables.cc
new file mode 100644
index 000000000..71c404a0e
--- /dev/null
+++ b/src/libutil/environment-variables.cc
@@ -0,0 +1,51 @@
+#include <cstring>
+#include <map>
+#include <optional>
+#include <string>
+
+extern char * * environ __attribute__((weak));
+
+namespace nix {
+
+std::optional<std::string> getEnv(const std::string & key)
+{
+    char * value = getenv(key.c_str());
+    if (!value) return {};
+    return std::string(value);
+}
+
+std::optional<std::string> getEnvNonEmpty(const std::string & key) {
+    auto value = getEnv(key);
+    if (value == "") return {};
+    return value;
+}
+
+std::map<std::string, std::string> getEnv()
+{
+    std::map<std::string, std::string> env;
+    for (size_t i = 0; environ[i]; ++i) {
+        auto s = environ[i];
+        auto eq = strchr(s, '=');
+        if (!eq)
+            // invalid env, just keep going
+            continue;
+        env.emplace(std::string(s, eq), std::string(eq + 1));
+    }
+    return env;
+}
+
+
+void clearEnv()
+{
+    for (auto & name : getEnv())
+        unsetenv(name.first.c_str());
+}
+
+void replaceEnv(const std::map<std::string, std::string> & newEnv)
+{
+    clearEnv();
+    for (auto & newEnvVar : newEnv)
+        setenv(newEnvVar.first.c_str(), newEnvVar.second.c_str(), 1);
+}
+
+}