Execute system commands without invoking system shell

Changes after a code review:

- fixed documentation for the closeBackground function
- renamed ```app``` parameter to ```cmd```

2 files changed, 16 insertions, 18 deletions

diff --git a/include/mts/MTS_System.h b/include/mts/MTS_System.h
index 6bca21b..cd9b9dd 100644
--- a/include/mts/MTS_System.h
+++ b/include/mts/MTS_System.h
@@ -71,12 +71,12 @@ namespace MTS {
              * A safer alternative to System::cmd that allows to execute applications with controlled
              * list of arguments bypasing the system shell.
              *
-             * \param  app    name of the application to be executed
+             * \param  cmd    name of the application to be executed
              * \param  argv   vector of arguments (excluding argument zero)
              * \param  result stdout output from the application is stored here
              * \return result code as for std::system and UNIX pclose
              */
-            static int32_t execute(const std::string& app, const std::vector<std::string>& argv, std::string& result);
+            static int32_t execute(const std::string& cmd, const std::vector<std::string>& argv, std::string& result);
 
             //! Spawn a process and open pipe with the specified type (READ or WRITE)
             /*!
@@ -84,18 +84,16 @@ namespace MTS {
             * list of arguments bypasing the system shell. If succeded, information about the spawned
             * process is written to the \p child structure.
             *
-            * \param  app  name of the application to be executed
+            * \param  cmd  name of the application to be executed
             * \param  argv vector of arguments (excluding argument zero)
             * \param  type open pipe for read from child or write to child
             * \return true on success, false on failure
             */
-            static bool executeBackground(const std::string& app, const std::vector<std::string>& argv, PipeType type, ChildHandle& child);
+            static bool executeBackground(const std::string& cmd, const std::vector<std::string>& argv, PipeType type, ChildHandle& child);
 
             //! Close the pipe and wait for a child to finish execution
             /*!
-            * \param  child  name of the application to be executed
-            * \param  argv   vector of arguments (excluding argument zero)
-            * \param  result stdout output from the application is stored here
+            * \param  child  structure with child process information as populated by executeBackground
             * \return result code as for std::system and UNIX pclose
             */
             static int closeBackground(ChildHandle& child);
@@ -103,13 +101,13 @@ namespace MTS {
         private:
 
             //! Spawn a process and open pipe with the specified type (READ or WRITE)
-            static bool executeBackground(const std::string& app, char* const argv[], PipeType type, ChildHandle& child);
+            static bool executeBackground(const std::string& cmd, char* const argv[], PipeType type, ChildHandle& child);
 
             //! Utility method. Cast argument to a C pointer required by some C-style functions.
             static inline char* castArgument(const std::string& arg);
 
             //! Utility method. Convert argument vector to a format required by execve and posix_spawn.
-            static std::vector<char*> castArgVector(const std::string& app, const std::vector<std::string>& argv);
+            static std::vector<char*> castArgVector(const std::string& cmd, const std::vector<std::string>& argv);
 
             //! Lightweight C++ wrapper with auto-close for file descriptors
             class FdWrapper {
diff --git a/src/MTS_System.cpp b/src/MTS_System.cpp
index 6acf065..31976e1 100644
--- a/src/MTS_System.cpp
+++ b/src/MTS_System.cpp
@@ -172,7 +172,7 @@ int32_t System::readFile(const std::string& path, std::string& result) {
     return 0;
 }
 
-int32_t System::execute(const std::string& app, const std::vector<std::string>& argv, std::string& result) {
+int32_t System::execute(const std::string& cmd, const std::vector<std::string>& argv, std::string& result) {
     // Ported directly from System::cmd
     std::string output;
     const int max_buffer = 256;
@@ -180,7 +180,7 @@ int32_t System::execute(const std::string& app, const std::vector<std::string>&
     int32_t code = -1;
     ChildHandle child;
 
-    if (executeBackground(app, argv, PipeType::READ, child)) {
+    if (executeBackground(cmd, argv, PipeType::READ, child)) {
         while (!feof(child.stream)) {
             if (fgets(buffer, max_buffer, child.stream) != NULL) {
                 output.append(buffer);
@@ -194,9 +194,9 @@ int32_t System::execute(const std::string& app, const std::vector<std::string>&
     return code;
 }
 
-bool System::executeBackground(const std::string& app, const std::vector<std::string>& argv, System::PipeType type, System::ChildHandle& child) {
-    std::vector<char*> arguments = castArgVector(app, argv);
-    return executeBackground(app, arguments.data(), type, child);
+bool System::executeBackground(const std::string& cmd, const std::vector<std::string>& argv, System::PipeType type, System::ChildHandle& child) {
+    std::vector<char*> arguments = castArgVector(cmd, argv);
+    return executeBackground(cmd, arguments.data(), type, child);
 }
 
 int System::closeBackground(System::ChildHandle& child) {
@@ -212,7 +212,7 @@ int System::closeBackground(System::ChildHandle& child) {
     return pstat;
 }
 
-bool System::executeBackground(const std::string& app, char* const argv[], System::PipeType type, ChildHandle& child) {
+bool System::executeBackground(const std::string& cmd, char* const argv[], System::PipeType type, ChildHandle& child) {
     pid_t childPid;
     FILE* stream = NULL;
     posix_spawn_file_actions_t actions;
@@ -262,7 +262,7 @@ bool System::executeBackground(const std::string& app, char* const argv[], Syste
             break;
         }
 
-        if (posix_spawnp(&childPid, app.c_str(), &actions, NULL, argv, NULL) != 0) {
+        if (posix_spawnp(&childPid, cmd.c_str(), &actions, NULL, argv, NULL) != 0) {
             // failed to spawn the process
             break;
         }
@@ -294,11 +294,11 @@ char* System::castArgument(const std::string& arg) {
     return const_cast<char*>(arg.c_str());
 }
 
-std::vector<char*> System::castArgVector(const std::string& app, const std::vector<std::string>& argv) {
+std::vector<char*> System::castArgVector(const std::string& cmd, const std::vector<std::string>& argv) {
     std::vector<char*> result;
 
     // Append application name as argument zero
-    result.push_back(castArgument(app));
+    result.push_back(castArgument(cmd));
 
     // Append all other arguments
     for (const std::string& arg : argv) {