Replace a string based on input


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# 1  
Replace a string based on input

I am trying to read a value from a mapping file and would need to replace the value based on country parameter
Code:
source_table_@ctry_final
Expected
final_var=source_table_aus_final

Code:
If the country is in nz,usa,uk then 
final_var=diff_table_nz_final
final_var=diff_table_usa_final
like that

else
final_var=source_table_aus_final

Code:

My try
Code:
final_var=$(echo "source_table_@ctry_final"| sed -e "s/\@ctry/${ctry_input}/")

# 2  
Please state the operating system, including version, and the shell you are using.

This works in ksh93 (Version AJM 93u+ 2012-08-01) on Ubuntu 18.04.3 LTS:
Code:
$ src=source_table_@ctry_final
$ rplst=nz,usa,uk
$ echo ${src/@ctry/{$rplst}}
source_table_nz_final source_table_usa_final source_table_uk_final

Strangely enough, it doesn't work with bash (4.4.20(1)-release):
Code:
$ echo ${src/ctry/{$rplst}}
source_table_{nz,usa,uk_final}

If anybody knows why, could we start a new thread on this, uh, feature?
[..]

Last edited by Scrutinizer; 08-20-2019 at 07:23 AM..
# 3  
Quote:
Originally Posted by apmcd47
...
Strangely enough, it doesn't work with bash (4.4.20(1)-release):
Code:
$ echo ${src/ctry/{$rplst}}
 source_table_{nz,usa,uk_final}

...

In bash, the unloved, deprecated eval helps:


Code:
eval echo ${src/@ctry/{$rplst\}}
 source_table_nz_final source_table_usa_final source_table_uk_final

and, no, the $ and { need to be in that sequence in order to make it a "brace expansion", which, in turn, can only be recognized / evaluated by the evil eval.
This User Gave Thanks to RudiC For This Post:
# 4  
But expected would be below. source string needs to be replaced with diff

Code:
diff_table_usa_final

Shell is bash
# 5  
Quote:
Originally Posted by Master_Mind
I am trying to read a value from a mapping file and would need to replace the value based on country parameter
How is that "country parameter" supplied and evaluated?
Quote:
Code:
source_table_@ctry_final
Expected
final_var=source_table_aus_final

The @ctry part has which value, for _aus_ to be part of the final string?

Quote:
Code:
If the country is in nz,usa,uk then 
 final_var=diff_table_nz_final
final_var=diff_table_usa_final
like that

else
 final_var=source_table_aus_final

Which table is relevant - diff_table or source_table - or is the distinction part of the problem?



Quote:
Code:

My try
Code:
final_var=$(echo "source_table_@ctry_final"| sed -e "s/\@ctry/${ctry_input}/")

What is and which value has ctry_input? Where does it come into play?
# 6  
It is because of the parsing order of the shell. In bash brace expansions are performed before any of the other expansions, hence the need for eval (usual caution applies (security)!) for a second round of expansions after the first round.

Last edited by Scrutinizer; 08-20-2019 at 07:35 AM..
# 7  
Unlike bash, ksh93 seems to do variable expansion before brace expansion. (Scrutinizer just said it.)

Master_Mind, I am not fully getting your requirement, but here is how you can adjust the ctry_input variable
Code:
#!/bin/sh
ctry_input=$1
case $ctry_input in
nz|usa|uk)
;;
*)
  ctry_input=aus
;;
esac
sed "s/@ctry/$ctry_input/"

This sample script you can run with a "uk" or "usa" argument, for example
Code:
sh sample.sh uk < inputfile

--- Post updated at 12:39 ---

To meet your sourc/diff replacement requirement, you can move the sed into the case-branch:
Code:
#!/bin/sh
ctry_input=$1
case $ctry_input in
nz|usa|uk)
  sed "s/@ctry/$ctry_input/
  s/source_table/diff_table/"
;;
*)
  ctry_input=aus
  sed "s/@ctry/$ctry_input/"
;;
esac

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