[util] add RunCommandParseJSON

src/util/system.cpp

@@ -6,6 +6,10 @@
 #include <sync.h>
 #include <util/system.h>
 
+#ifdef HAVE_BOOST_PROCESS
+#include <boost/process.hpp>
+#endif // HAVE_BOOST_PROCESS
+
 #include <chainparamsbase.h>
 #include <util/strencodings.h>
 #include <util/string.h>
@@ -1161,6 +1165,43 @@ void runCommand(const std::string& strCommand)
 }
 #endif
 
+#ifdef HAVE_BOOST_PROCESS
+UniValue RunCommandParseJSON(const std::string& str_command, const std::string& str_std_in)
+{
+    namespace bp = boost::process;
+
+    UniValue result_json;
+    bp::opstream stdin_stream;
+    bp::ipstream stdout_stream;
+    bp::ipstream stderr_stream;
+
+    if (str_command.empty()) return UniValue::VNULL;
+
+    bp::child c(
+        str_command,
+        bp::std_out > stdout_stream,
+        bp::std_err > stderr_stream,
+        bp::std_in < stdin_stream
+    );
+    if (!str_std_in.empty()) {
+        stdin_stream << str_std_in << std::endl;
+    }
+    stdin_stream.pipe().close();
+
+    std::string result;
+    std::string error;
+    std::getline(stdout_stream, result);
+    std::getline(stderr_stream, error);
+
+    c.wait();
+    const int n_error = c.exit_code();
+    if (n_error) throw std::runtime_error(strprintf("RunCommandParseJSON error: process(%s) returned %d: %s\n", str_command, n_error, error));
+    if (!result_json.read(result)) throw std::runtime_error("Unable to parse JSON: " + result);
+
+    return result_json;
+}
+#endif // HAVE_BOOST_PROCESS
+
 void SetupEnvironment()
 {
 #ifdef HAVE_MALLOPT_ARENA_MAX

src/util/system.h

@@ -37,6 +37,8 @@
 
 #include <boost/thread/condition_variable.hpp> // for boost::thread_interrupted
 
+class UniValue;
+
 // Application startup time (used for uptime calculation)
 int64_t GetStartupTime();
 
@@ -96,6 +98,16 @@ std::string ShellEscape(const std::string& arg);
 #if HAVE_SYSTEM
 void runCommand(const std::string& strCommand);
 #endif
+#ifdef HAVE_BOOST_PROCESS
+/**
+ * Execute a command which returns JSON, and parse the result.
+ *
+ * @param str_command The command to execute, including any arguments
+ * @param str_std_in string to pass to stdin
+ * @return parsed JSON
+ */
+UniValue RunCommandParseJSON(const std::string& str_command, const std::string& str_std_in="");
+#endif // HAVE_BOOST_PROCESS
 
 /**
  * Most paths passed as configuration arguments are treated as relative to