Help with storing awk output in variable

Question

I'm trying to write a shell script that does the viginere cypher with a given text and key and can't figure out how to save the new ascii number for the converted char in a variable. Code down below:

function encode {
  local message=$1
  local key=$2
  local encoded=""
  for ((i=0; i<${#message}; i++)); do
    local m=`echo $message | cut -c $((i+1))`
    local k=`echo $key | cut -c $((i%${#key}+1))`
    local m_ascii=`printf "%d" "'$m"`
    local k_ascii=`printf "%d" "'$k"`
    local e_ascii=$(((m_ascii + k_ascii - 2*97) % 26 + 97))
    local e=echo "&e_ascii" | awk '{ printf("%c",$0); }'
    encoded="$encoded$e"
  done
  echo $encoded
}

I also have the same problem in the respective decode function.

Answer 1

The way to run a shell command with awk variables by concatenation:

message="foobar"
cmd="echo \047"message"\047 | cut -c 3"
if ( (cmd | getline m) > 0 ) { print m }
else { print "Failed ..." | "cat>&2"; exit 1}
close(cmd)

Thanks Ed Morton, my first attempt was:

message="foobar"
"echo "message" | cut -c 3" | getline m
print m

Answer 2

Change echo "&e_ascii" to echo "$e_ascii" and e=echo ... to e=$(echo ...) then copy/paste your code into http://shellcheck.net and I expect it'll tell you how to fix the remaining issues.

Don't use a shell to manipulate text anyway, though, use a text processing tool like awk. This, using GNU awk for the ordchr library, is my just trying to implement your script line by line so I may have got parts wrong and/or there may be a better way and it's untested since you didn't provide any sample input/output:

encode() {
  awk -v message="$1" -v key="$2" '
    @load "ordchr"
    BEGIN {
      msgLgth = length(message)
      keyLgth = length(key)
      for ( i=0; i<msgLgth; i++ ) {
        m = substr(message,i+1,1)
        k = substr(key,(i % keyLgth) + 1,1)
        m_ascii = ord(m)
        k_ascii = ord(k)
        e_ascii = (m_ascii + k_ascii - 2*97) % 26 + 97
        e = chr(e_ascii)
        encoded = encoded e
      }
      print encoded
    }
  '
}

If you don't have GNU awk then see https://www.gnu.org/software/gawk/manual/html_node/Ordinal-Functions.html for one way to write ord() and chr() functions.