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。

  1. a=8
  3. # 下面所有这些比较的结果都应该是相等的
  4. test "$a" -lt 16 && echo "yes, $a < 16"         # "and list"
  5. /bin/test "$a" -lt 16 && echo "yes, $a < 16" 
  6. [ "$a" -lt 16 ] && echo "yes, $a < 16" 
  7. [[ $a -lt 16 ]] && echo "yes, $a < 16"          # 为表达式添加
  8. (( a < 16 )) && echo "yes, $a < 16"             # [[ ]]和(( ))并不是必须的
  10. city="New York"
  11. # 下面这些结果也是相等的
  12. test "$city" \< Paris && echo "Yes, Paris is greater than $city"
  13.                                   # ASCII字符比较
  14. /bin/test "$city" \< Paris && echo "Yes, Paris is greater than $city" 
  15. [ "$city" \< Paris ] && echo "Yes, Paris is greater than $city" 
  16. [[ $city < Paris ]] && echo "Yes, Paris is greater than $city"
  17.                                   # 并不需要为$city变量加引号。
  19. # 向S.C.致谢