How to remove spaces from a string in Lua?

Question

I want to remove all spaces from a string in Lua. This is what I have tried:

string.gsub(str, \"\", \"\")
string.gsub(str, \"% \", \"\")
string.gsub(str, \"%s*\"         


        

Answer 1

The fastest way is to use trim.so compiled from trim.c:

/* trim.c - based on http://lua-users.org/lists/lua-l/2009-12/msg00951.html
            from Sean Conner */
#include 
#include 
#include 
#include 

int trim(lua_State *L)
{
 const char *front;
 const char *end;
 size_t      size;

 front = luaL_checklstring(L,1,&size);
 end   = &front[size - 1];

 for ( ; size && isspace(*front) ; size-- , front++)
   ;
 for ( ; size && isspace(*end) ; size-- , end--)
   ;

 lua_pushlstring(L,front,(size_t)(end - front) + 1);
 return 1;
}

int luaopen_trim(lua_State *L)
{
 lua_register(L,"trim",trim);
 return 0;
}

compile something like:

gcc -shared -fpic -O -I/usr/local/include/luajit-2.1 trim.c -o trim.so

More detailed (with comparison to the other methods): http://lua-users.org/wiki/StringTrim

Usage:

local trim15 = require("trim")--at begin of the file
local tr = trim("   a z z z z z    ")--anywhere at code