摘要： : "${LOG_FILE:=/var/log/factory_install.log}" Shell Parameter Expansioin ${parameter:=word} If parameter is unset or null, the expansion of word is as 阅读全文

摘要： true && echo “a” || echo “b” result :a false && echo “a” || echo “b” result : b 阅读全文

摘要： Log in to your system and type echo $SHELL at the prompt. You will see a response containing sh, csh, ksh or b ash. You need to find out where bash is 阅读全文