How to use `while read` (Bash) to read the last line in a file if there’s no newline at the end of the file?

Question

Let’s say I have the following Bash script:

while read SCRIPT_SOURCE_LINE; do
  echo \"$SCRIPT_SOURCE_LINE\"
done

I noticed that for files

Answer 1

@Netcoder's answer is good, this optimisation eliminates spurious blank lines, also allows for the last line not to have a newline, if that's how the original was.

DONE=false
NL=
until $DONE ;do
if ! read ; then DONE=true ; NL='-n ';fi
echo $NL$REPLY
done

I used a variant of this to create 2 functions to allow piping of text that includes a '[' to keep grep happy. (you can add other translations)

function grepfix(){
    local x="$@";
    if [[ "$x" == '-' ]]; then
      local DONE=false
      local xx=
      until $DONE ;do
         if ! IFS= read ; then DONE=true ; xx="-n "; fi
         echo ${xx}${REPLY//\[/\\\[}
      done
    else
      echo "${x//\[/\\\[}"
    fi
 }


 function grepunfix(){
    local x="$@";
    if [[ "$x" == '-' ]]; then
      local DONE=false
      local xx=
      until $DONE ;do
         if ! IFS= read ; then DONE=true ; xx="-n "; fi
         echo ${xx}${REPLY//\\\[/\[}
      done
    else
      echo "${x//\\\[/\[}"
    fi
 }

(passing - as $1 enables pipe otherwise just translates arguments)