Thursday, April 7, 2022

[SOLVED] Bash: How to change only one parameter value and keep the other remain same

Issue

I have a bash script that edits two tags in a yaml file and these values are passed as parameters. How can I change the script for a scenario where only one tag has to be updated

#!/bin/bash

#Update UI-ImageTag
sed -i -e '/APP:/{n;n;s/\(imageTag\).*/\1: "'"app-ui-$1"'" /}' \
       -e '/APP:/{n;n;n;n;s/\(imageTag\).*/\1: "'"app-db-$2"'" /}' \
       values.yaml

While running the script and passing values for parameters $1 and $2 Ex(./script.sh 1.0 2.0) both the tags are updated in the values.yaml file, but when I give value for only one parameter and leave the other one empty(i.e., execute the script by passing value for $1 only), then the $2 tag in values.yaml file is replaced with an empty value. How to change the script so that in a scenario where I dont need to change the tag of app-db and if I dont pass a value for $2, it keeps the old value in the yaml file unchanged


Solution

Suggesting try awk script:

awk '
/APP:/{skip2 = 3; skip4 = 5}
!skip2 && inp1 {$0 = gensub("(imageTag)","\\1: \"app-ui-"inp1"\" \\\\",1)}
!skip4 && inp2 {$0 = gensub("(imageTag)","\\1: \"app-db-"inp2"\" \\\\",1)}
{print; --skip2; --skip4}
' inp1="$1" inp2="$2" values.yaml > values.yaml.1
mv values.yaml.1 values.yaml

Not tested, not provided sample data.

Explanation:

awk ' # start awk script
/APP:/ { # for evey line matching RegExp /APP:/ set down counter to skipped line
  skip2=3; # set skip2 action to next 2 lines including this is 3
  skip4=5; # set skip4 action to next 4 lines including this is 5
}
skip2 == 0 && inp1 { # in current line, if skip2 reached 0, and variable inp1 exist
  $0 = gensub("(imageTag)","\\1: \"app-ui-"inp1"\" \\\\",1); # do string subtition using gensub functin on current line.
}
skip4 == 0  && inp2 { # in current line, if skip4 reached 0, and variable inp2 exist
  $0 = gensub("(imageTag)","\\1: \"app-db-"inp2"\" \\\\",1); # do string subtition using gensub functin on current line.
}
{  # on every line
  print $0; # print current line
  --skip2;  # decrement skip2
  --skip4;  # decrement skip4
}' \  # end awk script
inp1="$1" \  # assign 1st script argument to awk variable inp1
inp2="$2" \  # assign 2nd script argument to awk variable inp1
values.yaml > values.yaml.1 # redirect output to values.yaml.1
mv values.yaml.1 values.yaml # override output to values.yaml


Answered By - Dudi Boy
Answer Checked By - David Goodson (WPSolving Volunteer)
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