平凡的幸福(備站）

主要是用z"$a" == z來判斷是否為Null或是空值 bash-3.2# vi test.sh #!/bin/bash if [ z"$a" == z ]; then echo "a is null" fi bash-3.2# ./test.sh a is null bash-3.2# vi test.sh #!/bin/bash a="" if [ z"$a" == z ]; then echo "a is null" bash-3.2# ./test.sh a is null fi