How can I run `done < <(curl -sL file.txt);` in older versions (1993-12-28) of ksh or update to bash?

Question

I have a script that runs flawlessly on many of the servers required. But recently it's failed on servers with old ksh versions.

Can you help me fix the offending line:

#!/bin/ksh
SUCCESS=0
FAILURE=0
while read IP
do
    CURL=$(curl -s -m 2 -x http://$IP -L http://icanhazip.com)
    if  [[ "${IP%%:*}" == "${CURL%%:*}" ]] ; then
        SUCCESS=$[SUCCESS+1]
        echo "$IP   ✓"
    else
        FAILURE=$[FAILURE+1]
        echo "$IP   X"
    fi
done < <(curl -sL vpn-proxy-list.txt);
echo "✓: $SUCCESS   X: $FAILURE"

The final line returns:

line 3: syntax error at line 14: `<(' unexpected

Unfortunately I'm unable to update ksh.

Can you help me make the done < <(curl -sL vpn-proxy-list.txt); portion simply work in bash? Or compatible with older versions (1993) of ksh?

Answer 1

You don't appear to be doing anything in the while body that cause trouble if it was run in a subshell, so I'd just stick with a plain pipline:

#!/bin/ksh

curl -sL vpn-proxy-list.txt | while read -r ip; do
    output=$(curl -s -m 2 -x "http://$ip" -L http://icanhazip.com)
    if  [[ "${ip%%:*}" == "${output%%:*}" ]]; then
        echo "$ip   Y"
    else
        echo "$ip   X"
    fi
done

---

Now you're asking something that breaks because you're making variable changes in a subshell, and those variables disappear when the subshell exits. A workaround: use grouping braces

curl -sL vpn-proxy-list.txt | {
    success=0
    failure=0
    while read -r ip; do
        output=$(curl -s -m 2 -x "http://$ip" -L http://icanhazip.com)
        if  [[ "${ip%%:*}" == "${output%%:*}" ]]; then
            echo "$ip   Y"
            let success+=1
        else
            echo "$ip   X"
            let failure+=1
        fi
    done
    echo there were $success successes
    echo there were $failure failures
}
# variables "success" and "failure" don't exist here.

Answer 2

You could make use of named pipes.

mkfifo foobar
curl -sL vpn-proxy-list.txt > foobar &
# Maybe sleep for a while here
while read -r IP; do
  # do something here
done < foobar
rm foobar