Dynamic case statement in bash

Question

I\'m trying to figure out how to create a dynamic case statement in a bash script.

For example, let\'s say I have the output of an awk statement with the following c

Answer 1

You can approach this in a couple of different hacky ways:

pattern=($(awk_command))     # red\ngreen\nblue\n
saveIFS=$IFS
IFS='|'
pattern="^(${pattern[*]})$"  # ^(red|green|blue)$  (perhaps hackish)
IFS=$saveIFS

# simple regex match if statement (not hackish)
if [[ $var =~ $pattern ]]
then
    do_something
fi

# or a backwards case statement (very hackish)
case 1 in    # this could be a variable or a command substitution
    $([[ $var =~ $pattern]] && echo 1) )  # the echo 1 could be another command or the 1 could be yet another variable
        do_something;;
    * )
        do_default;;
esac

Answer 2

A case statement is probably not the right tool for the job. If you store the awk output in an array then you can loop through the array to find if a choice is in it, and as a bonus can figure out which index that is, too.

#!/bin/bash

# Store command output in an array so each word is a separate array item.    
list=($(echo $'red\ngreen\nblue'))
my_var=blue

for ((i = 0; i < ${#list}; i++)); do
    if [[ ${list[$i]} = $my_var ]]; then
        echo "found at index $i"
        break
    fi
done

if ((i == ${#list})); then
    echo "not found"
fi

Answer 3

You can't do this with a case statement, but it's easy enough to set up your own helper to check for list membership.

# stub to simulate this arbitrary call
my_awk_command() { printf '%s\n' red green blue; }
# helper to check list membership
list_contains() {
  local tgt="$1"; shift
  while (( $# )); do
    if [[ $1 = "$tgt" ]] ; then
      return 0
    fi
    shift
  done
  return 1
}

# the below is Bash 4 functionality; see BashFAQ #1 on how to replace it
readarray -t awk_output < <(my_awk_command)

if list_contains "$my_var" "${my_awk_command[@]}"; then
  ...something...
elif [[ "$my_var" = something_else ]] ; then
  ...something else...
fi

Answer 4

might you have to try, sorry if this might to be oot/didnt you guys looking for, (but i think it's help me out) here i have same issues to using wheter sh case with dynamic statement

whereas i have running some function with dynamic listed parameter as input then if there's no function inside/available, it will return exit 1 or "requested not available"

here we go.

myfuncA(){
   echo this funcA
}

myfuncB(){
   echo this funcB
}


dynamicCase(){
   for areWe in $1; do
      my$areWe && echo "$areWe success" || echo "no function $1 available"
   done
}

anotherDyCase(){
   while IFS=read -r $areWe; do
      my$areWe && echo "$areWe success" || echo "no function $1 "
   done <<< $1
}

test ride:

myListedDynamic="funcA\nfuncB\nfuncC"
// funcA funcB funcC


dynamicCase $myListedDynamic
// success
// success
// no function available

furthermore

hope help

Answer 5

You can create a dynamic case statement in bash by doing the following:

1) ensure the list is PIPE (|) seperated. IE. red|green|blue

2) wrap your case statement in an eval

For example:

valid="red|green|blue"

eval "case \"$choice\" in
    $valid)
        echo do something good here
        ;;
    *)
        echo invalid colour
        ;;
esac"

This works for simple variable processing, I can not guarantee this will work in all cases.