Shell Programming and Scripting

cap
CAP
Cap
cAp
caP
CAp
cAP
CaP

echo "cap" | awk ' BEGIN {
        j = 1
} {
        len = length ($0)

        printf "%s\n", toupper($0)
        printf "%s\n", tolower($0)

        while ( j <= len )
        {
                for ( i = 1; i <= len; i++ )
                {
                        if ( i == j )
                                printf toupper(substr($0,i,1))
                        else
                                printf tolower(substr($0,i,1))
                }
                printf "\n"
                for ( i = 1; i <= len; i++ )
                {
                        if ( i == j )
                                printf tolower(substr($0,i,1))
                        else
                                printf toupper(substr($0,i,1))
                }
                printf "\n"
                ++j
        }
} '

echo "test" | awk 'function mix(w,v,a) {
   for(i=length(w)-1;i>=0;i--) {
      if(v>=2^i){
          v=v-2^i
          a=toupper(substr(w,i+1,1)) a
      } else a=tolower(substr(w,i+1,1))a
    }
    return a
}
{for(v=0;v<2^length;v++) print mix($0, v)}'

test
Test
tEst
TEst
teSt
TeSt
tESt
TESt
tesT
TesT
tEsT
TEsT
teST
TeST
tEST
TEST

[Mm][Oo][Rr][Tt][Gg][Aa][Gg][Ee]

$ echo mortgage | awk '{for(i=1;i<NF;i++) printf "[%c%c]",toupper($i),tolower($i); printf "\n"}' FS=
[Mm][Oo][Rr][Tt][Gg][Aa][Gg][Ee]

echo "mortage" | awk  '{for (i=1;i<=NF;i++) printf "["toupper($i)$i"]"} END {print ""}' FS=""
[Mm][Oo][Rr][Tt][Aa][Gg][Ee]

echo viagra | awk_operation
Result:
(?i\)\\b[Vv].?[Ii].?[Aa].?[Gg].?[Rr].?[Aa]\\b

Similary
echo good | awk_opearation
Result:
(?i\)\\b[Gg].?[Oo].?[Oo].?[Dd]\\b