Sstrhsrtj

I have a complex string of this form:

inp="key1 =   what' ever the value key2 = the value Nb.2   key3= "last value""

I need to get the first key associated with its first value. I want to use bash regex to extract the key, the value, and what remains from the string:

rkeyval="[[:space:]]*([_[:alnum:]]*?)[[:space:]]*=[[:space:]]*((.*?)[[:space:]]+([_[:alnum:]]+?[[:space:]]*=[[:space:]]*.*))"



if [[ $inp =~ $rkeyval ]]; then



  key=${BASH_REMATCH[1]}

  val=${BASH_REMATCH[3]}

  left=${BASH_REMATCH[4]}



  for i in $(seq 0 $(( ${#BASH_REMATCH[*]}-1 ))); do  

    echo -e "$i: "${BASH_REMATCH[$i]}""; 

  done; 

else

  echo "no match"

fi

This does not work. On my Mac with Bash 4.4, there is no match:

no match

On my Red Hat Linux, I get the following output:

0: "key1 =   what' ever the value key2 = the value Nb.2   key3= "last value""

1: "key1"

2: "what' ever the value key2 = the value Nb.2   key3= "last value""

3: "what' ever the value key2 = the value Nb.2  "

4: "key3= "last value""

I expect the following output:

0: "key1 =   what' ever the value key2 = the value Nb.2   key3= "last value""

1: "key1"

2: "what' ever the value key2 = the value Nb.2   key3= "last value""

3: "what' ever the value"

4: "key3= "last value""

In other words, the key would be the second matching group, and the value the third.

This expression works on an online PHP regexp tester.

I want this to work in any Unix machine having an updated version of Bash.

I don't know why this does not work, and why the result differ from one platform to another, even though my regex respects the Posix convention (or does it?). What am I doing wrong here?

An asterisk is already an optional count (as it could be zero characters). There is no need to add an ? to it.

So, Will it be ok if each parenthesis will capture a key or a value?:

s='[[:space:]]*'        # spaces

n='[_[:alnum:]]+'       # a valid name (limited by spaces)

e="${s}=${s}"           # an equal sign (=).



rkeyval="${s}(${n})${e}([^=]*) (${n})${e}([^=]*) (${n})${e}(.*)"

#            1^^^^^    2^^^^^^ 3^^^^^    4^^^^^^ 5^^^^^    6^^^

echo "$rkeyval"

That will capture like this:

if [[ $inp =~ $rkeyval ]]; then



    i=0

    while ((i<${#BASH_REMATCH[@]})); do

        printf '%s: "%s"n' "$((i))" "${BASH_REMATCH[i++]}";

    done

else

    echo "no match"

fi

Printing:

0: "key1 =   what' ever the value key2 = the value Nb.2   key3= "last value""

1: "key1"

2: "what' ever the value"

3: "key2"

4: "the value Nb.2  "

5: "key3"

6: ""last value""

And the values you want (if I understand your code correctly) could be approximated by (edit to get a perfect match):

key="${BASH_REMATCH[1]}"

val="${BASH_REMATCH[@]:2:3}"

left="${BASH_REMATCH[@]:5:2}"

POSIX does not define *? for EREs, which Bash uses, instead specifying that:

The behavior of multiple adjacent duplication symbols ( '+', '*', '?', and intervals) produces undefined results.

Bash uses the system regcomp/regexec for regular-expression matching. Apple's libc presumably does not implement the behaviour you want for *?.

There is no standard way to recover non-greedy matching semantics from greedy, though in this case at least some of them are unnecessary (the first [_[:alnum:]]*?, for example). Otherwise, you need to transform the expression to match something else or mutate the data in advance (and probably afterwards) to get the effect.