cat <<EOT >> greetings.txt
line 1
line 2
EOT方法二：
echo "line 1
line 2" >> greetings.txt参考：
shell – How to append multiple lines to a file – Unix & Linux Stack Exchange
cat <<EOT >> greetings.txt
line 1
line 2
EOT方法二：
echo "line 1
line 2" >> greetings.txt参考：
shell – How to append multiple lines to a file – Unix & Linux Stack Exchange