diff --git a/src/api/process.c b/src/api/process.c
index e71785cb..f2a1b1c2 100644
--- a/src/api/process.c
+++ b/src/api/process.c
@@ -12,26 +12,133 @@
 
 #define READ_BUF_SIZE 4096
 
+#define L_GETTABLE(L, idx, key, conv, def) (  \
+    lua_getfield(L, idx, key),                \
+    conv(L, -1, def)                          \
+)
+
+#define L_GETNUM(L, idx, key, def) L_GETTABLE(L, idx, key, luaL_optnumber, def)
+#define L_GETSTR(L, idx, key, def) L_GETTABLE(L, idx, key, luaL_optstring, def)
+
+#define L_SETNUM(L, idx, key, n) (lua_pushnumber(L, n), lua_setfield(L, idx - 1, key))
+
+#define L_RETURN_REPROC_ERROR(L, code) {      \
+    lua_pushnil(L);                           \
+    lua_pushstring(L, reproc_strerror(code)); \
+    lua_pushnumber(L, code);                  \
+    return 3;                                 \
+}
+
+#define ASSERT_MALLOC(ptr)                      \
+    if (ptr == NULL)                            \
+        L_RETURN_REPROC_ERROR(L, REPROC_ENOMEM)
+
+#define ASSERT_REPROC_ERRNO(L, code) { \
+    if (code < 0)                      \
+        L_RETURN_REPROC_ERROR(L, code) \
+}
+
 typedef struct {
     reproc_t * process;
-    lua_State* L;
-
+    bool running;
+    int returncode;
 } process_t;
 
+// this function should be called instead of reproc_wait
+static int poll_process(process_t* proc, int timeout)
+{
+    int ret = reproc_wait(proc->process, timeout);
+    if (ret != REPROC_ETIMEDOUT) {
+        proc->running = false;
+        proc->returncode = ret;
+    }
+    return ret;
+}
+
 static int process_new(lua_State* L)
 {
-    process_t* self = (process_t*) lua_newuserdata(
-        L, sizeof(process_t)
+    int cmd_len = lua_rawlen(L, 1) + 1;
+    const char** cmd = malloc(sizeof(char *) * cmd_len);
+    ASSERT_MALLOC(cmd);
+    cmd[cmd_len] = NULL;
+
+    for(int i = 0; i < cmd_len; i++) {
+        lua_rawgeti(L, 1, i + 1);
+
+        cmd[i] = luaL_checkstring(L, -1);
+        lua_pop(L, 1);
+    }
+
+    int deadline = L_GETNUM(L, 2, "timeout", 0);
+    const char* cwd =L_GETSTR(L, 2, "cwd", NULL);
+    int redirect_in = L_GETNUM(L, 2, "stdin", REPROC_REDIRECT_DEFAULT);
+    int redirect_out = L_GETNUM(L, 2, "stdout", REPROC_REDIRECT_DEFAULT);
+    int redirect_err = L_GETNUM(L, 2, "stderr", REPROC_REDIRECT_DEFAULT);
+    lua_pop(L, 5); // remove args we just read
+
+    if (
+        redirect_in > REPROC_REDIRECT_STDOUT
+        || redirect_out > REPROC_REDIRECT_STDOUT
+        || redirect_err > REPROC_REDIRECT_STDOUT)
+    {
+        lua_pushnil(L);
+        lua_pushliteral(L, "redirect to handles, FILE* and paths are not supported");
+        return 2;
+    }
+
+    // env
+    luaL_getsubtable(L, 2, "env");
+
+    lua_pushnil(L); 
+    int env_len = 1;
+    while (lua_next(L, -2) != 0) {
+        env_len++;
+        lua_pop(L, 1);
+    }
+
+    const char** env = malloc(sizeof(char *) * env_len);
+    ASSERT_MALLOC(env);
+    env[env_len] = NULL;
+
+    int i = 0;
+    lua_pushnil(L);
+    while (lua_next(L, -2) != 0) {
+        lua_pushliteral(L, "=");
+        lua_pushvalue(L, -3); // push the key to the top
+        lua_concat(L, 3); // key=value
+
+        env[i++] = luaL_checkstring(L, -1);
+        lua_pop(L, 1);
+    }
+
+    reproc_t* proc = reproc_new();
+    int out = reproc_start(
+        proc,
+        (const char* const*) cmd,
+        (reproc_options) {
+            .working_directory = cwd,
+            .deadline = deadline,
+            .nonblocking = true,
+            .env = {
+                .behavior = REPROC_ENV_EXTEND,
+                .extra = env
+            },
+            .redirect = {
+                .in.type = redirect_in,
+                .out.type = redirect_out,
+                .err.type = redirect_err
+            }
+        }
     );
 
-    memset(self, 0, sizeof(process_t));
+    ASSERT_REPROC_ERRNO(L, out);
 
-    self->process = NULL;
-    self->L = L;
-
-    luaL_getmetatable(L, API_TYPE_PROCESS);
-    lua_setmetatable(L, -2);
+    process_t* self = lua_newuserdata(L, sizeof(process_t));
+    self->process = proc;
+    self->running = true;
 
+    // this is equivalent to using lua_setmetatable()
+    luaL_setmetatable(L, API_TYPE_PROCESS);
     return 1;
 }
 
@@ -39,24 +146,24 @@ static int process_strerror(lua_State* L)
 {
     int error_code = luaL_checknumber(L, 1);
 
-    if(error_code){
-        lua_pushstring(
-            L,
-            reproc_strerror(error_code)
-        );
-    } else {
+    if (error_code < 0)
+        lua_pushstring(L, reproc_strerror(error_code));
+    else
         lua_pushnil(L);
-    }
 
     return 1;
 }
 
-static int process_gc(lua_State* L)
+static int f_gc(lua_State* L)
 {
     process_t* self = (process_t*) luaL_checkudata(L, 1, API_TYPE_PROCESS);
 
-    if(self->process){
-        reproc_kill(self->process);
+    if(self->process) {
+        reproc_stop(self->process, (reproc_stop_actions) {
+            { REPROC_STOP_KILL, 0 },
+            { REPROC_STOP_KILL, 0 },
+            { REPROC_STOP_TERMINATE, 0 }
+        });
         reproc_destroy(self->process);
         self->process = NULL;
     }
@@ -64,78 +171,23 @@ static int process_gc(lua_State* L)
     return 0;
 }
 
-static int process_start(lua_State* L)
+static int f_pid(lua_State* L)
 {
     process_t* self = (process_t*) lua_touserdata(L, 1);
 
-    luaL_checktype(L, 2, LUA_TTABLE);
-
-    char* path = NULL;
-    size_t path_len = 0;
-
-    if(lua_type(L, 3) == LUA_TSTRING){
-        path = (char*) lua_tolstring(L, 3, &path_len);
-    }
-
-    size_t deadline = 0;
-
-    if(lua_type(L, 4) == LUA_TNUMBER){
-        deadline = lua_tonumber(L, 4);
-    }
-
-    size_t table_len = luaL_len(L, 2);
-    char* command[table_len+1];
-    command[table_len] = NULL;
-
-    int i;
-    for(i=1; i<=table_len; i++){
-        lua_pushnumber(L, i);
-        lua_gettable(L, 2);
-
-        command[i-1] = (char*) lua_tostring(L, -1);
-
-        lua_remove(L, -1);
-    }
-
-    if(self->process){
-        reproc_kill(self->process);
-        reproc_destroy(self->process);
-    }
-
-    self->process = reproc_new();
-
-    int out = reproc_start(
-        self->process,
-        (const char* const*) command,
-        (reproc_options){
-            .working_directory = path,
-            .deadline = deadline,
-            .nonblocking=true,
-            .redirect.err.type=REPROC_REDIRECT_PIPE
-        }
-    );
-
-    if(out > 0) {
-        lua_pushboolean(L, 1);
-    }
-    else {
-        reproc_destroy(self->process);
-        self->process = NULL;
-        lua_pushnumber(L, out);
-    }
-
+    lua_pushnumber(L, reproc_pid(self->process));
     return 1;
 }
 
-static int process_pid(lua_State* L)
+static int f_returncode(lua_State *L)
 {
-    process_t* self = (process_t*) lua_touserdata(L, 1);
+    process_t* self = (process_t*) luaL_checkudata(L, 1, API_TYPE_PROCESS);
+    int ret = poll_process(self, 0);
 
-    if(self->process){
-        lua_pushnumber(L, reproc_pid(self->process));
-    } else {
-        lua_pushnumber(L, 0);
-    }
+    if (self->running)
+        lua_pushnil(L);
+    else
+        lua_pushnumber(L, ret);
 
     return 1;
 }
@@ -143,239 +195,180 @@ static int process_pid(lua_State* L)
 static int g_read(lua_State* L, int stream)
 {
     process_t* self = (process_t*) lua_touserdata(L, 1);
+    unsigned long read_size = luaL_optunsigned(L, 2, READ_BUF_SIZE);
 
-    if(self->process){
-        int read_size = READ_BUF_SIZE;
-        if (lua_type(L, 2) == LUA_TNUMBER){
-            read_size = (int) lua_tonumber(L, 2);
-        }
+    luaL_Buffer b;
+    uint8_t* buffer = (uint8_t*) luaL_buffinitsize(L, &b, read_size);
 
-        int tries = 1;
-        if (lua_type(L, 3) == LUA_TNUMBER){
-            tries = (int) lua_tonumber(L, 3);
-        }
+    int out = reproc_read(
+        self->process,
+        stream,
+        buffer,
+        read_size
+    );
 
-        int out = 0;
-        uint8_t buffer[read_size];
+    if (out >= 0)
+        luaL_addsize(&b, out); 
+    luaL_pushresult(&b);
 
-        int runs;
-        for (runs=0; runs<tries; runs++){
-            out = reproc_read(
-                self->process,
-                REPROC_STREAM_OUT,
-                buffer,
-                read_size
-            );
-
-            if (out >= 0)
-                break;
-        }
-
-        if(out == REPROC_EPIPE){
-            reproc_kill(self->process);
-            reproc_destroy(self->process);
-            self->process = NULL;
-
-            lua_pushnil(L);
-        } else if(out > 0) {
-            lua_pushlstring(L, (const char*) buffer, out);
-        } else {
-            lua_pushnil(L);
-        }
-    } else {
-        lua_pushnil(L);
-    }
+    if (out == REPROC_EPIPE)
+        ASSERT_REPROC_ERRNO(L, out);
 
     return 1;
 }
 
-static int process_read(lua_State* L)
+static int f_read_stdout(lua_State* L)
 {
     return g_read(L, REPROC_STREAM_OUT);
 }
 
-static int process_read_errors(lua_State* L)
+static int f_read_stderr(lua_State* L)
 {
     return g_read(L, REPROC_STREAM_ERR);
 }
 
-static int process_write(lua_State* L)
+static int f_read(lua_State* L)
+{
+    int stream = luaL_checknumber(L, 1);
+    lua_remove(L, 1); // remove the number we just read
+    return g_read(L, stream);
+}
+
+static int f_write(lua_State* L)
 {
     process_t* self = (process_t*) lua_touserdata(L, 1);
 
-    if(self->process){
-        size_t data_size = 0;
-        const char* data = luaL_checklstring(L, 2, &data_size);
+    size_t data_size = 0;
+    const char* data = luaL_checklstring(L, 2, &data_size);
 
-        int out = 0;
-
-        out = reproc_write(
-            self->process,
-            (uint8_t*) data,
-            data_size
-        );
-
-        if(out == REPROC_EPIPE){
-            reproc_kill(self->process);
-            reproc_destroy(self->process);
-            self->process = NULL;
-        }
-
-        lua_pushnumber(L, out);
-    } else {
-        lua_pushnumber(L, REPROC_EPIPE);
-    }
+    int out = reproc_write(
+        self->process,
+        (uint8_t*) data,
+        data_size
+    );
+    if (out == REPROC_EPIPE)
+        L_RETURN_REPROC_ERROR(L, out);
 
+    lua_pushnumber(L, out);
     return 1;
 }
 
-static int process_close_stream(lua_State* L)
+static int f_close_stream(lua_State* L)
 {
     process_t* self = (process_t*) lua_touserdata(L, 1);
 
-    if(self->process){
-        size_t stream = luaL_checknumber(L, 2);
-
-        int out = reproc_close(self->process, stream);
-
-        lua_pushnumber(L, out);
-    } else {
-        lua_pushnumber(L, REPROC_EINVAL);
-    }
+    int stream = luaL_checknumber(L, 2);
+    int out = reproc_close(self->process, stream);
+    ASSERT_REPROC_ERRNO(L, out);
 
+    lua_pushboolean(L, 1);
     return 1;
 }
 
-static int process_wait(lua_State* L)
+static int f_wait(lua_State* L)
 {
     process_t* self = (process_t*) lua_touserdata(L, 1);
+    
+    int timeout = luaL_optnumber(L, 2, 0);
+    
+    int ret = poll_process(self, timeout);
+    // negative returncode is also used for signals on POSIX
+    if (ret == REPROC_ETIMEDOUT)
+        ASSERT_REPROC_ERRNO(L, ret);
 
-    if(self->process){
-        size_t timeout = luaL_checknumber(L, 2);
-
-        int out = reproc_wait(self->process, timeout);
-
-        if(out >= 0){
-            reproc_destroy(self->process);
-            self->process = NULL;
-        }
-
-        lua_pushnumber(L, out);
-    } else {
-        lua_pushnumber(L, REPROC_EINVAL);
-    }
-
+    lua_pushnumber(L, ret);
     return 1;
 }
 
-static int process_terminate(lua_State* L)
+static int f_terminate(lua_State* L)
 {
     process_t* self = (process_t*) lua_touserdata(L, 1);
 
-    if(self->process){
-        int out = reproc_terminate(self->process);
+    int out = reproc_terminate(self->process);
+    ASSERT_REPROC_ERRNO(L, out);
 
-        if(out < 0){
-            lua_pushnumber(L, out);
-        } else {
-            reproc_destroy(self->process);
-            self->process = NULL;
-            lua_pushboolean(L, 1);
-        }
-    } else {
-        lua_pushnumber(L, REPROC_EINVAL);
-    }
+    poll_process(self, 0);
 
+    lua_pushboolean(L, 1);
     return 1;
 }
 
-static int process_kill(lua_State* L)
+static int f_kill(lua_State* L)
 {
     process_t* self = (process_t*) lua_touserdata(L, 1);
 
-    if(self->process){
-        int out = reproc_kill(self->process);
+    int out = reproc_kill(self->process);
+    ASSERT_REPROC_ERRNO(L, out);
 
-        if(out < 0){
-            lua_pushnumber(L, out);
-        } else {
-            reproc_destroy(self->process);
-            self->process = NULL;
-            lua_pushboolean(L, 1);
-        }
-    } else {
-        lua_pushnumber(L, REPROC_EINVAL);
-    }
+    poll_process(self, 0);
 
+    lua_pushboolean(L, 1);
     return 1;
 }
 
-static int process_running(lua_State* L)
+static int f_running(lua_State* L)
 {
     process_t* self = (process_t*) lua_touserdata(L, 1);
-
-    if(self->process){
-        lua_pushboolean(L, 1);
-    } else {
-        lua_pushboolean(L, 0);
-    }
+    
+    poll_process(self, 0);
+    lua_pushboolean(L, self->running);
 
     return 1;
 }
 
 static const struct luaL_Reg process_methods[] = {
-    { "__gc", process_gc},
-    {"start", process_start},
-    {"pid", process_pid},
-    {"read", process_read},
-    {"read_errors", process_read_errors},
-    {"write", process_write},
-    {"close_stream", process_close_stream},
-    {"wait", process_wait},
-    {"terminate", process_terminate},
-    {"kill", process_kill},
-    {"running", process_running},
+    { "__call", process_new },
+    { "__gc", f_gc},
+    {"pid", f_pid},
+    {"returncode", f_returncode},
+    {"read", f_read},
+    {"read_stdout", f_read_stdout},
+    {"read_stderr", f_read_stderr},
+    {"write", f_write},
+    {"close_stream", f_close_stream},
+    {"wait", f_wait},
+    {"terminate", f_terminate},
+    {"kill", f_kill},
+    {"running", f_running},
     {NULL, NULL}
 };
 
-static const struct luaL_Reg process[] = {
-    {"new", process_new},
+static const struct luaL_Reg lib[] = {
     {"strerror", process_strerror},
-    {"ERROR_PIPE", NULL},
-    {"ERROR_WOULDBLOCK", NULL},
-    {"ERROR_TIMEDOUT", NULL},
-    {"STREAM_STDIN", NULL},
-    {"STREAM_STDOUT", NULL},
-    {"STREAM_STDERR", NULL},
-    {NULL, NULL}
+    {"Process", NULL},
+    {"CONSTANTS", NULL}
 };
 
 int luaopen_process(lua_State *L)
 {
+    luaL_newlib(L, lib);
+
     luaL_newmetatable(L, API_TYPE_PROCESS);
     luaL_setfuncs(L, process_methods, 0);
     lua_pushvalue(L, -1);
     lua_setfield(L, -2, "__index");
+    lua_setfield(L, -2, "Process"); // process.Process
 
-    luaL_newlib(L, process);
+    lua_newtable(L);
+    L_SETNUM(L, -1, "ERROR_INVAL", REPROC_EINVAL);
+    L_SETNUM(L, -1, "ERROR_TIMEDOUT", REPROC_ETIMEDOUT);
+    L_SETNUM(L, -1, "ERROR_PIPE", REPROC_EPIPE);
+    L_SETNUM(L, -1, "ERROR_NOMEM", REPROC_ENOMEM);
+    L_SETNUM(L, -1, "ERROR_WOULDBLOCK", REPROC_EWOULDBLOCK);
 
-    lua_pushnumber(L, REPROC_EPIPE);
-    lua_setfield(L, -2, "ERROR_PIPE");
+    L_SETNUM(L, -1, "WAIT_INFINITE", REPROC_INFINITE);
+    L_SETNUM(L, -1, "WAIT_DEADLINE", REPROC_DEADLINE);
 
-    lua_pushnumber(L, REPROC_EWOULDBLOCK);
-    lua_setfield(L, -2, "ERROR_WOULDBLOCK");
+    L_SETNUM(L, -1, "STREAM_STDIN", REPROC_STREAM_IN);
+    L_SETNUM(L, -1, "STREAM_STDOUT", REPROC_STREAM_OUT);
+    L_SETNUM(L, -1, "STREAM_STDERR", REPROC_STREAM_ERR);
 
-    lua_pushnumber(L, REPROC_ETIMEDOUT);
-    lua_setfield(L, -2, "ERROR_TIMEDOUT");
-
-    lua_pushnumber(L, REPROC_STREAM_IN);
-    lua_setfield(L, -2, "STREAM_STDIN");
-
-    lua_pushnumber(L, REPROC_STREAM_OUT);
-    lua_setfield(L, -2, "STREAM_STDOUT");
-
-    lua_pushnumber(L, REPROC_STREAM_ERR);
-    lua_setfield(L, -2, "STREAM_STDERR");
+    L_SETNUM(L, -1, "REDIRECT_DEFAULT", REPROC_REDIRECT_DEFAULT);
+    L_SETNUM(L, -1, "REDIRECT_PIPE", REPROC_REDIRECT_PIPE);
+    L_SETNUM(L, -1, "REDIRECT_PARENT", REPROC_REDIRECT_PARENT);
+    L_SETNUM(L, -1, "REDIRECT_DISCARD", REPROC_REDIRECT_DISCARD);
+    L_SETNUM(L, -1, "REDIRECT_STDOUT", REPROC_REDIRECT_STDOUT);
+    lua_setfield(L, -2, "CONSTANTS"); // process.CONSTANTS
 
     return 1;
 }