【Bash】ファイルの文字列を分割し、条件を満たす文字列のみを出力する方法

import re
import sys

input_file = sys.argv[1]
header = sys.argv[2]
header_pat = re.compile('^>(.*)')
is_target_section = False

with open(input_file) as f:
    for line in f:
        if m := header_pat.match(line):
            is_target_section = m[1] == header
        if is_target_section:
            print(line, end='')

% python3 filter.py input.txt 'America/NICD-N20214/2021'
>America/NICD-N20214/2021
CTTTAAAAGATCTGTTCTCT
AAACGAAATCTGTGTGGCTG
TCACTCGGCTGCATGC

#!/bin/bash

readonly INPUT=./input.txt
readonly OUTPUT=./output.txt
readonly TARGET_HEADER=America/NICD-N20214/2021

cat /dev/null >${OUTPUT}

in_section=0
while read line; do
  if [ "$(echo ${line} | cut -c 1)" = ">" ]; then
    if [ ${in_section} -eq 1 ]; then
      break
    elif [ "$(echo ${line} | cut -c 2-)" = "${TARGET_HEADER}" ]; then
      in_section=1
      echo ${line} >>${OUTPUT}
    fi
  else
    if [ ${in_section} -eq 1 ]; then
      echo ${line} >>${OUTPUT}
    fi
  fi
done <${INPUT}

cat 69GB.log | awk -v RS=">" -f 69GB.awk > print.log
awk -v RS=">" -f 69GB.awk　69GB.log > print.log

/^¥/America¥/NICD¥-N20214¥/2021.*$/ {
   printf(">%s", $0)
   # or　print(">" $0)
   next
}
/正規表現/{
  printf(">%s", $0)
  next
}