Is there any special bash reserved characters in bash regex expression?

• ex:

  • eg: if [[ $url =~ ^https:\/\/www\.youtube\.com\/playlist\?(.+&)?list= ]]; then echo "URL matches the regex"; fi
    This is just a normal regex test.

• problem:

  • Do I need to be careful about special case where:
    I have things like eg: %VAR%, $VAR, &VAR, (or any potential special bash reserved characters), inside my regex expression.
    Do I need to escape those?
  • eg: if [[ $url =~ ^https:\/\/%VAR%/$VAR/&VAR/!@#$%^&*()-=_+/wte;/ ]]; then echo "URL matches the regex"; fi
    // assume I intentionally need to match such regex

• ex:

  • for example, I know that ' or " certainly have special meanings when they are at the ends.
    • https://stackoverflow.com/questions/218156/bash-regex-with-quotes
    • eg: if [[ $url =~ '^https:\/\/www\.youtube\.com\/playlist\?(.+&)?list=' ]]; then echo "Screw up"; fi

• again:

  • I am not asking about escaping the regex (I know how to use regex, be it PCRE or ERE doesnt matter.)
  • I am asking about escaping the bash reserved special characters, when inside a regex expression, if there is any.

• In another words, is the regex expression in bash

  • more like /^http:\/\/www/g in js literal regex, where the inside will always be literal regex;
  • or more like "^http:\\/\\/www" in js RegExp, where you need to escape the reserved characters ' " ` \ etc due to being inside a string

Update:

• For "Is there any special bash reserved characters in bash regex expression?"
  The simple answer is yes.

• As for an example:

  url="https://www.youtube.com/playlist?list=PLmHVyfmcRKyxvxehq3fiGjKDsEyy6d4Tz"
  regex='^https:\/\/www\.youtube\.com\/playlist\?(.+&)?list='
  
  idx=0
  (( idx++ )) # normal
  if [[ $url =~ ^https:\/\/www\.youtube\.com\/playlist\?(.+&)?list= ]]; then echo "URL matches the regex - $idx"; fi
  (( idx++ )) # normal
  if [[ $url =~ $regex ]]; then echo "URL matches the regex - $idx"; fi
  (( idx++ ))
  yt='www\.youtube\.com\/'
  if [[ $url =~ ^https:\/\/${yt}playlist\?(.+&)?list= ]]; then echo "URL matches the regex - $idx"; fi
  (( idx++ ))
  if [[ $url =~ ^https:\/\/'${yt}'playlist\?(.+&)?list= ]]; then echo "URL matches the regex - $idx"; fi
  (( idx++ ))
  if [[ $url =~ '^https:\/\/'${yt}'playlist\?'(.+&)?list= ]]; then echo "URL matches the regex - $idx"; fi
  

• I guess its better to change the question:
  from
  "Is there any special bash reserved characters in bash regex expression?"
  to
  "How quotes work in bash regex expression? (Regarding special regex reserved character & special bash reserved characters.)"

• (Was expecting a way to write literal regex, that would be so much easier, seems not possible.)

Update:

For what literal regex that I want means:

text='The pizza is 2'\'' and 100$price' # The pizza is 2' and 100$price

# literal regex I want: [0-9]+' and [0-9]+\$price
regex="[0-9]+' and [0-9]+\\\$price"
if [[ "$text" =~ $regex ]]; then echo "this is the normal way of doing things, do you see I need to escape the \ & $ ?"; fi
# if [[ "$text" =~ [0-9]+' and [0-9]+\$price ]]; then echo "this is what I prefer to have -- literal regex, like / /g in js. But this wont even compile"; fi