linux - Bash redirect vs. pipe -

i have following bash script:

#!/bin/bash  trap "trap - sigterm && kill -- -$$" sigint sigterm  proxy_list="${1}" url="google.com" pool=5 timeout=2  check_proxy() {     local socks_proxy="${1}"     retry in {0..2};         time_connect="$(curl ${url} --socks5 ${socks_proxy} -m${timeout} -o /dev/null -s -w %{time_connect})"         if [ $? -eq 0 ];             echo "${socks_proxy} (${time_connect}s) retries=${retry}"             break         fi     done }  while read proxy;     while true;         if [ "$(jobs -rp | wc -l)" -lt "${pool}" ];             check_proxy "${proxy}" &             break         fi         wait -n     done done < "${proxy_list:-/dev/stdin}"  wait 

the script either use filename (${1}) input, or stdin if no positional parameter provided.

(pipe) if run script follows , try kill ctrl+c during runtime:

cut -f1 -d' ' data/socks_tested_sorted.list | ./curl_socks_tester.sh 

i error , script continues running:

./curl_socks_tester.sh: line 1: kill: (-21325) - no such process

(redirect) alternatively running command , killing script using ctrl+c:

./curl_socks_tester.sh <(cut -f1 -d' ' data/socks_tested_sorted.list) 

the script stops , following message:

^cterminated

why trap able kill child-processes when using redirect fails using pipe?

the way bash runs jobs, first link in pipe-line becomes group leader (as should able verify ps).

consequently, in:

cut -f1 -d' ' data/socks_tested_sorted.list | ./curl_socks_tester.sh 

./curl_socks_tester.sh not group leader , kill -- -$$ invalid.

you can use kill -- -$$ in script if can sure shell script leader of process group.