Re: string.format(%q) and escape sequences

[Philipp Janda <siffiejoe@...>]

Am 13.08.2013 20:23 schröbte Bernd Eggink:
> The documentation says, "the q option formats a string between double
> quotes, using escape sequences when necessary to ensure that it can
> safely be read back by the Lua interpreter".
> However, this is not true if the string contains certain escape
> sequences, such as \027 or \013:
>
>      t="\027[1maha\027[m"
>      t1=string.format("%q", t)    --> "\27[1maha\27[m"
>
> On an xterm in Linux print(t) prints a nice bold aha, while print(t1)
> prints "\27[1maha\27[m". Is that a bug or am I missing something?

Yes, you are missing the "can safely be read back by the Lua 
interpreter". You are not reading t1 back. Try this instead:

    t = "\027[1maha\027[m"
    print( t )
    file = assert( io.open( "f.lua", "w" ) )
    -- %q already includes double quotes at both ends ...:
    file:write( "print(", string.format( "%q", t ), ")\n" )
    file:close()
    dofile( "f.lua" )  -- do the reading back ...

So, the %q format specifier is for generating valid Lua string literals 
that can be pasted into a Lua program ...

> Bernd

Philipp