How to pipe input to a Bash while loop and preserve variables after loop ends

The correct notation for Process Substitution is:

while read i; do echo $i; done < <(echo "$FILECONTENT")

The last value of i assigned in the loop is then available when the loop terminates.An alternative is:

echo $FILECONTENT | {while read i; do echo $i; done...do other things using $i here...}

The braces are an I/O grouping operation and do not themselves create a subshell. In this context, they are part of a pipeline and are therefore run as a subshell, but it is because of the |, not the { ... }. You mention this in the question. AFAIK, you can do a return from within these inside a function.

Bash also provides the shopt builtin and one of its many options is:

lastpipe

If set, and job control is not active, the shell runs the last command of a pipeline not executed in the background in the current shell environment.

Thus, using something like this in a script makes the modfied sum available after the loop:

FILECONTENT="12 Name13 Number14 Information"shopt -s lastpipe   # Comment this out to see the alternative behavioursum=0echo "$FILECONTENT" |while read number name; do ((sum+=$number)); doneecho $sum

Doing this at the command line usually runs foul of 'job control is not active' (that is, at the command line, job control is active). Testing this without using a script failed.

Also, as noted by Gareth Rees in his answer, you can sometimes use a here string:

while read i; do echo $i; done <<< "$FILECONTENT"

This doesn't require shopt; you may be able to save a process using it.

Jonathan Leffler explains how to do what you want using process substitution, but another possibility is to use a here string:

while read i; do echo "$i"; done <<<"$FILECONTENT"

This saves a process.

This function makes duplicates $NUM times of jpg files (bash)

function makeDups() {NUM=$1echo "Making $1 duplicates for $(ls -1 *.jpg|wc -l) files"ls -1 *.jpg|sort|while read fdo  COUNT=0  while [ "$COUNT" -le "$NUM" ]  do    cp $f ${f//sm/${COUNT}sm}    ((COUNT++))  donedone}