Re: [PATCH] generic/581: remove extra escape character from awk line

["Luís Henriques" <henrix@camandro.org>]

(Sorry for replying from private email address)

On Wed, Nov 22, 2023 at 03:16:48PM -0800, Eric Biggers wrote:
> On Wed, Nov 22, 2023 at 05:03:24PM +0000, Luis Henriques wrote:
> > Checking the keys in /proc/key-users is buggy, as there's an extra '\'
> > character: in '{print \$4}' the '$4' shouldn't be escaped otherwise the
> > 'awk' command will fail.  This has passed unnoticed because the output
> > is sent to '_user_do' function and the result assigned to a variable.
> > 
> > While there, replace 'awk' by $AWK_PROG.
> > 
> > Signed-off-by: Luis Henriques <lhenriques@suse.de>
> > ---
> >  tests/generic/581 | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > Hi!
> > 
> > Please note that I'm not an 'awk' expert and I may be wrong!  But if I do
> > see an error if I run something like:
> > 
> > $ awk '/^[[:space:]]*1000:/{print \$4}' /proc/key-users 
> > awk: cmd. line:1: /^[[:space:]]*1000:/{print \$4}
> > awk: cmd. line:1:                            ^ backslash not last character on line
> > 
> > But maybe this depends on the awk implementation, although I've tried a few.
> > 
> > diff --git a/tests/generic/581 b/tests/generic/581
> > index cabc7e1c69ab..1a4b571d40ce 100755
> > --- a/tests/generic/581
> > +++ b/tests/generic/581
> > @@ -92,7 +92,7 @@ while grep -E -q '^[0-9a-f]+ [^ ]*i[^ ]*' /proc/keys; do
> >  done
> >  
> >  # Set the user key quota to the fsgqa user's current number of keys plus 5.
> > -orig_keys=$(_user_do "awk '/^[[:space:]]*$(id -u fsgqa):/{print \$4}' /proc/key-users | cut -d/ -f1")
> > +orig_keys=$(_user_do "$AWK_PROG '/^[[:space:]]*$(id -u fsgqa):/{print $4}' /proc/key-users | cut -d/ -f1")
> 
> The backslash is needed to prevent $4 from being expanded by bash, because the
> whole pipeline with 'awk' and 'cut' is in a double-quoted string:
> 
>     "awk '/^[[:space:]]*$(id -u fsgqa):/{print \$4}' /proc/key-users | cut -d/ -f1"
> 
> Without escaping the $, bash would replace $4 with the empty string while it's
> doing expansions on the whole double-quoted string.

/me blushes

Yeah, looking closer it makes sense.  Sorry for the noise.  I'm currently
investigating a test failure (which I can't reproduce locally) where
'orig_key' unexpectedly is set to '1' and makes the test fail because it
was supposed to be '0'.  That's when this caught my attention.  Anyway,
I'll go look somewhere else.

Cheers,
--
Luís