shell 正则匹配字符

[root@yyjk tmp]#cat a1.sh
aaa=\'20190401.zip\'
if [[ "$aaa" =~ ^[0-9]{4}[0-9]{1,2}[0-9]{1,2}\.zip$ ]]; then
  echo \'aaaaaaaaaaaaaaa\'
else
  echo \'bbbbbbbbbbbbbbbb\'
fi
[root@yyjk tmp]#sh ./a1.sh
aaaaaaaaaaaaaaa



[root@yyjk tmp]#cat a1.sh
aaa=\'x20190401.zip\'
if [[ "$aaa" =~ ^[0-9]{4}[0-9]{1,2}[0-9]{1,2}\.zip$ ]]; then
  echo \'aaaaaaaaaaaaaaa\'
else
  echo \'bbbbbbbbbbbbbbbb\'
fi
[root@yyjk tmp]#sh ./a1.sh
bbbbbbbbbbbbbbbb


[root@yyjk tmp]#cat a1.sh
aaa=\'20190401.zipx\'
if [[ "$aaa" =~ ^[0-9]{4}[0-9]{1,2}[0-9]{1,2}\.zip$ ]]; then
  echo \'aaaaaaaaaaaaaaa\'
else
  echo \'bbbbbbbbbbbbbbbb\'
fi
[root@yyjk tmp]#sh ./a1.sh
bbbbbbbbbbbbbbbb