init with uname

.gitignore

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+*.so

Makefile

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+cc = gcc
+CFLAGS := $(CFLAGS) -Wall -Wextra -D_GNU_SOURCE
+
+LIBFLAGS = $(pkg-config --libs --cflags lua)
+
+objs = uname.so
+
+all : $(objs)
+
+%.so : %.c %.h
+	$(cc) -o $@ $(CFLAGS) $(LIBFLAGS) -fPIC -shared $<
+
+.PHONY : clean
+clean :
+	-rm $(objs)

uname.c

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+#define _GNU_SOURCE 1
+#include <string.h>
+#include <stdio.h>
+#include <err.h>
+#include <errno.h>
+#include "uname.h"
+#include <lauxlib.h>
+#include <lua.h>
+#include <sys/utsname.h>
+
+#define ERRBUF_SIZE 1024
+
+static int l_numid(lua_State *L) {
+    lua_Number x = luaL_checknumber(L, 1);
+    printf("%f\n", x);
+    
+    lua_pushnumber(L, x);
+
+    return 1;
+}
+
+/*
+ * Add one
+ */
+long long plus_one(int x) {
+    return x + 1;
+}
+
+static int l_plus_one(lua_State *L) {
+    // argument number check is not conventional in lua?
+    int argc = lua_gettop(L);
+    if (argc != 1)
+        return luaL_error(L, "Invalid number of argument");
+
+    // Type check and get
+    lua_Integer x = luaL_checkinteger(L, 1);
+
+    lua_Integer result = plus_one(x);
+
+    // Push the result
+    lua_pushinteger(L, result);
+    // How many elements from the top is return value
+    return 1;
+}
+
+static int l_uname(lua_State *L) {
+    struct utsname name;
+    if (uname(&name)) {
+        char errbuf[ERRBUF_SIZE];
+        if (strerror_r(errno, errbuf, ERRBUF_SIZE))
+            perror("Error while making error msg");
+        return luaL_error(L, errbuf);
+    }
+    lua_newtable(L);
+    lua_pushstring(L, "sysname");
+    lua_pushstring(L, name.sysname);
+    lua_settable(L, -3);
+    lua_pushstring(L, "machine");
+    lua_pushstring(L, name.machine);
+    lua_settable(L, -3);
+    lua_pushstring(L, "release");
+    lua_pushstring(L, name.release);
+    lua_settable(L, -3);
+    lua_pushstring(L, "version");
+    lua_pushstring(L, name.version);
+    lua_settable(L, -3);
+    return 1;
+}
+
+static const struct luaL_Reg llib_uname [] = {
+    {"uname", l_uname},
+    {"numid", l_numid},
+    {"plusone", l_plus_one},
+    {NULL, NULL},
+};
+
+// for `require`
+int luaopen_uname(lua_State *L) {
+    luaL_newlib(L, llib_uname);
+    return 1;
+}

uname.h

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+#ifndef L_UNAME_H
+#define L_UNAME_H
+#include <sys/utsname.h>
+#include <lua.h>
+#include <lualib.h>
+#include <lauxlib.h>
+
+long long plus_one(int x);
+
+static int l_numid(lua_State *L);
+static int l_plus_one(lua_State *L);
+static int l_uname(lua_State *L);
+
+int luaopen_uname(lua_State *L);
+
+#endif