我想将一个脚本加载到redis中,这将导出未来脚本执行所依赖的函数,但尝试定义全局函数失败,全局变量也是如此：
redis 127.0.0.1:6379> EVAL "function alex() return 3.1415 end" 0 (error) ERR Error running script (call to f_f24a5a054d91ccc74c2629e113f8f639bbedbfa2): user_script:1: Script attempted to create global variable 'alex'
如何定义全局函数和变量？
解决方法
查看文件scripting.c中的源代码
/* This function installs Metamethods in the global table _G that prevent * the creation of globals accidentally. * * It should be the last to be called in the scripting engine initialization * sequence,because it may interact with creation of globals. */ void scriptingEnableGlobalsProtection(lua_State *lua) { char *s[32]; sds code = sdsempty(); int j = 0; /* strict.lua from: http://Metalua.luaforge.net/src/lib/strict.lua.html. * Modified to be adapted to Redis. */ s[j++]="local mt = {}\n"; s[j++]="setMetatable(_G,mt)\n"; s[j++]="mt.__newindex = function (t,n,v)\n"; s[j++]=" if debug.getinfo(2) then\n"; s[j++]=" local w = debug.getinfo(2,\"S\").what\n"; s[j++]=" if w ~= \"main\" and w ~= \"C\" then\n"; s[j++]=" error(\"Script attempted to create global variable '\"..tostring(n)..\"'\",2)\n"; s[j++]=" end\n"; s[j++]=" end\n"; s[j++]=" rawset(t,v)\n"; s[j++]="end\n"; s[j++]="mt.__index = function (t,n)\n"; s[j++]=" if debug.getinfo(2) and debug.getinfo(2,\"S\").what ~= \"C\" then\n"; s[j++]=" error(\"Script attempted to access unexisting global variable '\"..tostring(n)..\"'\",2)\n"; s[j++]=" end\n"; s[j++]=" return rawget(t,n)\n"; s[j++]="end\n"; s[j++]=NULL; for (j = 0; s[j] != NULL; j++) code = sdscatlen(code,s[j],strlen(s[j])); luaL_loadbuffer(lua,code,sdslen(code),"@enable_strict_lua"); lua_pcall(lua,0); sdsfree(code); }
scriptingEnableGlobalsProtection的doc-string表明intent是通知脚本作者常见错误(不使用local).
可以删除此保护：
local mt = setMetatable(_G,nil) -- define global functions / variables function alex() return 3.1415 end -- return globals protection mechanizm setMetatable(_G,mt)
或者使用rawset：
local function alex() return 3.1415 end rawset(_G,"alex",alex)