初学shell，字符串比较所遇，求教！

lickakafirst

shell，字符串比较时，不清楚两个字符串比较的是什么，值大小，长度还是其他？求教！
如下：
1.
val1=hockey
val2=baseball

if [ $val1 \> $val2 ]
then
    echo "$val1 is greater than $val2"
else
    echo "$val1 is less than $val2"
fi
结果：
+ val1=hockey
+ val2=baseball
+ '[' hockey '>' baseball ']'
+ echo 'hockey is greater than baseball'
hockey is greater than baseball

tc1989tc

string1 > string2
              True  if string1 sorts after string2 lexicographically in the current locale.

应该是按照字典顺序一个字符一个字符的比较的。。

lickakafirst

这个代码比较的是字符串中单个字符的ascII码么？从高位开始逐次比较，直到某个字符的ascII码大于另外一个字符的，就得出结果？

tc1989tc

Following comment from http://stackoverflow.com/questio ... es-it-work-internal
       

From help test:

  STRING1 > STRING2
                 True if STRING1 sorts after STRING2 lexicographically.

Internally, bash either uses strcoll() or strcmp() for that:

else if ((op[0] == '>' || op[0] == '<') && op[1] == '\0')
  {
    if (shell_compatibility_level > 40 && flags & TEST_LOCALE)
      return ((op[0] == '>') ? (strcoll (arg1, arg2) > 0) : (strcoll (arg1, arg2) < 0));
    else
      return ((op[0] == '>') ? (strcmp (arg1, arg2) > 0) : (strcmp (arg1, arg2) < 0));
  }

The latter actually compares ASCII codes, the former (used when locale is enabled) performs a more specific comparison which is suitable for sorting in given locale.

yjh777

lickakafirst 发表于 2015-11-16 10:20
这个代码比较的是字符串中单个字符的ascII码么？从高位开始逐次比较，直到某个字符的ascII码大于另外一个字 ...

是的！