Escaping commands in script modules

sleve_mcdichael

I am having trouble getting a couple of commands to script properly.

First, to build the project from terminal, I need to type exactly:

CFLAGS='-DDATADIR="\"home/pi/RetroPie/roms/ports/CaveStory/nxengine-evo/data/\""' CXXFLAGS='-DDATADIR="\"/home/pi/RetroPie/roms/ports/CaveStory/nxengine-evo/data/\""' cmake -DCMAKE_BUILD_TYPE=Release -DPORTABLE=On ..

Substituting vars $romdir and $md_id, that looks like:

CFLAGS='-DDATADIR="\"$romdir/ports/CaveStory/$md_id/data/\""' CXXFLAGS='-DDATADIR="\"$romdir/ports/CaveStory/$md_id/data/\""' cmake -DCMAKE_BUILD_TYPE=Release -DPORTABLE=On ..

...but when I put that in my build function, something gets lost. When I run the binary, it reports: Error opening font file omdir/ports/CaveStory/d_id/data/font_1.fnt

It seems rather than being expanded properly, the vars are just omitting the first char after the $ sign (and the sign itself) and passing as omdir and d_id. How do I properly escape this command so that the vars will expand correctly? I tried just adding another \ before the $ but that didn't work either. Error was the same ("omdir/ports/CaveStory/d_id/data/").

Second, I need to move the contents of a directory one level up, and delete the empty dir.

I tried:

mv "$romdir/ports/CaveStory/$md_id/CaveStory/*" "$romdir/ports/CaveStory/$md_id"

...but the log shows: mv: cannot stat '/home/pi/RetroPie/roms/ports/CaveStory/nxengine-evo/CaveStory/*': No such file or directory

...and then of course rmdir failed, because the dir was not empty. I'm guessing it's because the * is inside the quotes because it doesn't work from command-line either:

mv "/home/pi/RetroPie/roms/ports/CaveStory/nxengine-evo/CaveStory/*" "/home/pi/RetroPie/roms/ports/CaveStory/nxengine-evo"
mv: cannot stat '/home/pi/RetroPie/roms/ports/CaveStory/nxengine-evo/CaveStory/*': No such file or directory

If I move the star outside the quotes, it works:

mv "/home/pi/RetroPie/roms/ports/CaveStory/nxengine-evo/CaveStory/"* "/home/pi/RetroPie/roms/ports/CaveStory/nxengine-evo"
pi@retropie: ~/RetroPie/roms/ports/CaveStory/nxengine-evo $

Is it "okay" to do this? I haven't tried it in the script yet, will it work there? Is there a better/other way?

mitu

You need to learn how Bash expands variables. Single quotes (') prevent variable expansion, while double quotes (") allow it.

$ var=X
$ echo '$var'
 $var
$ echo "$var"
X
$ echo '"$var"'
"$var"
$ echo "'$var'"
'X'

sleve_mcdichael

@mitu said in Escaping commands in script modules:

$ echo "'$var'"
'X'

So there's single quotes there, but they're inside of double ones. So it only depends on the outermost ones, or...? I tried swapping them in the command which didn't work, nor did using double-quotes exclusively (escaping the existing un-escaped doubles that were now inside the outer ones) or wrapping additional doubles around the whole thing, or various pieces of. Got any hints what else I might try?

Or, I understand if you don't want to be my bash teacher. Know of any resources that might help me understand?

Edit: ah, will this do it?

Inside single quotes everything is preserved literally, without exception.

That means you have to close the quotes, insert something, and then re-enter again.

'before'"$variable"'after'
'before'"'"'after'
'before'\''after'

...ooh when I do this, it highlights the vars in nano in a way it wasn't doing before. Thats promising?

 CFLAGS='-DDATADIR="\"'"$romdir"'/ports/CaveStory/'"$md_id"'/data/\""' CXXFLAGS='-DDATADIR="\"'"$romdir"'/ports/CaveStory/'"$md_id"'/data/\""' cmake -DCMAKE_BUILD_TYPE=Release -DPORTABLE=On ..

Edit again: yeah that seems to have done it, I guess I just needed to keep searching...

sleve_mcdichael

mv "$romdir/ports/CaveStory/$md_id/CaveStory/"* (...)

Is this right, though? Just close the quotes and leave a naked star outside them like that? It feels kind of...dirty to do it this way. Am I wrong? (It does work, though...)

mitu

@sleve_mcdichael said in Escaping commands in script modules:

Is this right, though?

It is, because the filename globbing for * doesn't happen inside the quoted string:

$ ls "~/roms/nes/*"
ls: cannot access 'roms/nes/*': No such file or directory
# tries to list a file named '*'

$ ls "~/roms/nes/"*
 roms/nes/240pee.nes                 roms/nes/game1.zip
... 

# filename expansion happens normally