test命令用于检查文件类型和比较值。同时还可以使用[作为测试命令。它用于:

• 文件属性的比较
• 字符串比较。
• 算法的比较。

语法

[ condition ]

或者

[ ! condition ]

或者

[ condition ] && true-command

或者

[ condition ] || false-command

或者

[ condition ] && true-command || false-command

示例

[ 5 == 5 ] && echo "Yes" || echo "No"
[ 5 == 15 ] && echo "Yes" || echo "No"
[ 5 != 10 ] && echo "Yes" || echo "No"

# 如果文件存在，则执行前面的echo语句，否则执行后面的echo
[ -f /etc/resolv.conf ] && echo "File /etc/resolv.conf found." || echo "File /etc/resolv.conf not found."
[ -f /etc/resolv1.conf ] && echo "File /etc/resolv.conf found." || echo "File /etc/resolv.conf not found."