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36.3 测试和比较的其他方法

对于判断(test命令)来说,[[ ]]比[ ]更加合适。同样的,算数运算符(译注:-eq之类的)比(( ))更有优势。
a=8
# 下面所有这些比较的结果都应该是相等的
test "$a" -lt 16 && echo "yes, $a < 16" # "and list"
/bin/test "$a" -lt 16 && echo "yes, $a < 16"
[ "$a" -lt 16 ] && echo "yes, $a < 16"
[[ $a -lt 16 ]] && echo "yes, $a < 16" # 为表达式添加
(( a < 16 )) && echo "yes, $a < 16" # [[ ]]和(( ))并不是必须的
city="New York"
# 下面这些结果也是相等的
test "$city" \< Paris && echo "Yes, Paris is greater than $city"
# ASCII字符比较
/bin/test "$city" \< Paris && echo "Yes, Paris is greater than $city"
[ "$city" \< Paris ] && echo "Yes, Paris is greater than $city"
[[ $city < Paris ]] && echo "Yes, Paris is greater than $city"
# 并不需要为$city变量加引号。
# 向S.C.致谢