Bash regex using BASH_REMATCH not capturing all groups [duplicate]

Question

In bash, I'm trying to capture this groups with this regex but BASH_REMATCH give me empty results

RESULT="1730624402|1*;[64452034;STOP;1730588408;74;22468;1"
regex="([[:digit:]]+)?|([[:digit:]])*;\[([[:digit:]]+)?;STOP;([[:digit:]]+)?;"

if [[ "$RESULT" =~ $regex ]]
    then
        echo "${BASH_REMATCH}"     # => 1730624402
        echo "${BASH_REMATCH[1]}"  # => 1730624402
        echo "${BASH_REMATCH[2]}"  # EMPTY
        echo "${BASH_REMATCH[3]}"  # EMPTY
        echo "${BASH_REMATCH[4]}"  # EMPTY
    else
        echo "check regex"
    fi

Where I go wrong?

Thanks in advance

please update the question to show the expected contents of BASH_REMATCH[] — markp-fuso
– markp-fuso, Commented Nov 3, 2024 at 21:24
You need to escape the special characters | and * as they are not interpreted literally. Try regex='([[:digit:]]+)?\|([[:digit:]])\*;\[([[:digit:]]+)?;STOP;([[:digit:]]+)?;' — pmf
– pmf, Commented Nov 3, 2024 at 21:29
To make it much easier, you can add this to replace all non-numbers with a space: RESULT="${RESULT//[!0-9]/ }" — Cyrus
– Cyrus, Commented Nov 3, 2024 at 21:51

markp-fuso · Accepted Answer · 2024-11-03 21:42:14Z

2

RESULT contains the literal characters | and *. These two characters have special meaning in regex's so they need to be escaped. (NOTE: [ also has special meaning but OP has correctly escaped it.)

One modification to OP's regex:

regex="([[:digit:]]+)\|([[:digit:]])\*;\[([[:digit:]]+);STOP;([[:digit:]]+);"
                     ^^             ^^
###########
# a shorter alternative:

regex="([0-9]+)\|([0-9])\*;\[([0-9]+);STOP;([0-9]+);"
               ^^       ^^

Taking for a test drive:

[[ "$RESULT" =~ $regex ]] && typeset -p BASH_REMATCH

declare -a BASH_REMATCH=([0]="1730624402|1*;[64452034;STOP;1730588408;" [1]="1730624402" [2]="1" [3]="64452034" [4]="1730588408")

NOTES:

OP hasn't (yet) stated the desired contents of BASH_REMATCH[] so at this point I'm guessing this is the expected result
in this particular case I don't see the need for the additional ? characters in the regex

edited Nov 3, 2024 at 21:42

answered Nov 3, 2024 at 21:37

markp-fuso

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