UNIX for Dummies Questions & Answers

$ bash4-4.2$ bash4 --version
GNU bash, version 4.2.0(1)-release (i386-apple-darwin12.2.0)
bash4-4.2$ declare -a lang=(cpp sql js h); ext=cpp; if [[ ${lang[@]} =~ $(echo "\\<${ext}\\>") ]]; then echo hello; fi
bash4-4.2$

$ bash --version
GNU bash, version 4.1.2(1)-release (x86_64-redhat-linux-gnu)
$ declare -a lang=(cpp sql js h); ext=cpp; if [[ ${lang[@]} =~ $(echo "\\<${ext}\\>") ]]; then echo hello; fi
hello

$ declare -a lang=(cpp sql js h); ext="\<cpp\>"; if [[ ${lang[@]} =~ ${ext} ]]; then echo hello; fi
hello

lang=(cpp sql js h)
ext='[[:<:]]cpp[[:>:]]'
if [[ ${lang[@]} =~ $ext ]]; then
  echo hello
fi

ext=cpp
declare -a lang=(cpp py sql cc h)
if [[ ${lang[@]} =~ $(printf %s "\<${ext}\>") ]]; then
        echo ${ext}
fi

if [[ ${lang[@]} =~ $(printf "%s" "[[:<:]]$ext[[:>:]]") ]]; then
   echo hello
fi

mtch="[[:<:]]$ext[[:>:]]"
if [[ ${lang[@]} =~ $mtch ]]; then
   echo hello
fi

declare -A lang=([cpp]=1 [sql]=1 [js]=1 [h]=1 [py]=1)
if [[ ${lang[$ext]} ]]; then echo hello; fi

if [[ " ${lang[*]} " == *" $ext "* ]]; then
   echo hello
fi

case " ${lang[*]} " in 
  (*" $ext "*) echo hello
esac

lang="cpp sql js h py"