Re: q// / qq// syntax or built-ins please ?

[Vladimir Marek]

While quoting can be difficult at time, one can make his life simpler

DELIM=\'
CHAR="[^$DELIM]"
REGEX="$CHAR*$DELIM($CHAR+)$DELIM$CHAR*"

$ echo "

Error: Cannot find file '/missing/file_1'.

Error: Cannot find file '/missing/file_2'.

" | while read line; do
        if [[ $line =~ $REGEX ]]; then
                echo "${BASH_REMATCH[1]}"
        fi
done
/missing/file_1
/missing/file_2


Care has to be taken though, CHAR can't be for example

CHAR=ab
WORD="$CHAR*"

as that becomes 'ab*' which is not '(ab)*'

Personally, I would probably use perl.

-- 
        Vlad


On Thu, Mar 23, 2017 at 08:40:35PM +0000, Jason Vas Dias wrote:
> Please , in some future versions of bash, could it provide
> support / help for avoiding "quoting hell", in such situations
> as :
> 
> $ echo "
> 
> Error: Cannot find file '/missing/file_1'.
> 
> Error: Cannot find file '/missing/file_2'.
> 
> "  |  while read line; do
>    cmd='if [[ '$'"'"$line"$'"'' =~
> ^[^'"\\'"']*['"\\'"']([^'"\\'"']+)['"\\'"'][^'"\\'"']*$ ]]; then echo
> ${BASH_REMATCH[1]}; fi;';
>   echo "$cmd" | bash -;
> done
> 
> See what I have to do to match lines containing a non-empty
> single-quoted string ?
> ie. I just want to cut-and-paste such lines from the output of some
> application, and
> weed out the empty lines and print the  single-quoted string in lines
> containing them (only!), with a simple bash command. If you replace
> "echo $cmd | bash -" with
> 'eval "$cmd"' , it does not work, because the double-quotes which I
> had painstakingly inserted with '$'"''  get removed somehow by eval -
> why is this?
> ie, only if "$line" is empty, does bash evaluate the text:
>    'if [[ "" = ... ]]; then ...'
> else, for the lines I want to match, it would evaluate eg. :
> + eval 'if [[ Error: Cannot find file '\''/missing_file_1'\''.\" =~
> ^[^\\\'\'']*[\\\'\'']([\\\'\'']+)[\\\'\''][^\\\'\'']*$ ]]; then echo
> ${BASH_REMATCH[1]}; fi;'
> + set +x
> ( nothing printed - the single quotes are stripped)
> + eval 'if [[ \"\" =~
> ^[^\\\'\'']*[\\\'\'']([\\\'\'']+)[\\\'\''][^\\\'\'']*$ ]]; then echo
> ${BASH_REMATCH[1]}; fi;'
> ++ [[ "" =~ ^[^\']*[\']([\']+)[\'][^\']*$ ]]
> + set +x
> +
> 
> I think bash needs some kind of "q/.../'" and 'qq/../' syntax / built-ins, or
> whatever syntax its author likes,  like PERL has, whereby the  single quote
> ("'") or double quote ('"') respectively are totally ignored within
> '/.../'  parameter
> strings, which should use a different quoting character than '"' or
> "'" to delineate
> them.
> 
> If the author won't develop these, I will & will send a patch.
> 
> Regards,
> Jason
>