Extracting substring within string between 2 token within the string
Hello.
First best wishes for everybody.
here is the input file ("$INPUT1") contents :
Code:
BASH_FUNC_message_begin_script%%=() { local -a L_ARRAY;
BASH_FUNC_message_debug%%=() { local -a L_ARRAY;
BASH_FUNC_message_end_script%%=() { local -a L_ARRAY;
BASH_FUNC_message_error%%=() { local -a L_ARRAY;
This simple sed command works well for some kind of tokens.
These tokens work well
Code:
TOKEN1="^BASH_FUNC_"
TOKEN2="\%\%\=\(\)"
#
# # between but excluding TOKEN1 and TOKEN2
#
sed -e 's/'$TOKEN1'\(.*\)'$TOKEN2'.*/\1/' "$INPUT1"
The curly braces for variable expansions are good practice within strings, for reasons of readability and also to prevent variable expansion errors.
--
What happens with the single quote construct is that the variable expansions are unprotected, and therefore the shell splits variable TOKEN2 into three fields local-a and L_ARRAY. These three fields are combined with the other characters passed as parameters to the sed command, effectively like so:
Code:
sed -e 's/^BASH_FUNC_\(.*\)local' -a 'L_ARRAY.*/\1/' # wrong
This is why sed complains of an unterminated s-command.
When you use double quotes this will not happen since the variables are expanded, but not field split by the shell, since they are protected by double quotes. Double quotes also allow for simpler and easier to read code..
Last edited by Scrutinizer; 01-03-2020 at 02:39 PM..
This User Gave Thanks to Scrutinizer For This Post:
sed 's/'"$TOKEN1"'\(.*\)'"$TOKEN2"'.*/\1/' "$INPUT1"
The point is, each $var must be within "quotes", so the shell does not do word splitting and filename generation.
Then it must be
Code:
TOKEN2="%%=()"
The ( ) is not special in a BRE, but \( \) is.
The -e (code argument follows) is allowed but not needed (because at least one code argument is required).
The curly braces for variable expansions are good practice within strings, for reasons of readability and also to prevent variable expansion errors.
--
What happens with the single quote construct is that the variable expansions are unprotected, and therefore the shell splits variable TOKEN2 into three fields local-a and L_ARRAY. These three fields are combined with the other characters passed as parameters to the sed command, effectively like so:
Code:
sed -e 's/^BASH_FUNC_\(.*\)local' -a 'L_ARRAY.*/\1/' # wrong
This is why sed complains of an unterminated s-command.
When you use double quotes this will not happen since the variables are expanded, but not field split by the shell, since they are protected by double quotes. Double quotes also allow for simpler and easier to read code..
Thank you very much
--- Post updated at 21:14 ---
Quote:
Originally Posted by MadeInGermany
Or
Code:
sed 's/'"$TOKEN1"'\(.*\)'"$TOKEN2"'.*/\1/' "$INPUT1"
The point is, each $var must be within "quotes", so the shell does not do word splitting and filename generation.
Then it must be
Code:
TOKEN2="%%=()"
The ( ) is not special in a BRE, but \( \) is.
The -e (code argument follows) is allowed but not needed (because at least one code argument is required).
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01-03-2020
