#!/usr/bin/env bash echo 'Using conditional expression:' [[ ' ' < '0' ]] && echo ok || echo not ok [[ ' a' < '0a' ]] && echo ok || echo not ok echo 'Using test:' [ ' ' \< '0' ] && echo ok || echo not ok [ ' a' \< '0a' ] && echo ok || echo not ok
输出是：
Using conditional expression: ok not ok Using test: ok ok
bash –version：GNU bash,版本4.2.45(1)-release(x86_64-pc-linux-gnu)
uname -a：Linux linuxmint 3.8.0-19-generic
Bash手册说：
原文链接：https://www.f2er.com/bash/384351.htmlWhen used with [[,the < and > operators sort lexicographically using the current locale. The test command sorts using ASCII ordering.
这归结为分别使用strcoll(3)或strcmp(3).
使用以下程序(strcoll_strcmp.c)来测试：
#include <stdio.h> #include <string.h> #include <locale.h> int main(int argc,char **argv) { setlocale(LC_ALL,""); if (argc != 3) { fprintf(stderr,"Usage: %s str1 str2\n",argv[0]); return 1; } printf("strcoll('%s','%s'): %d\n",argv[1],argv[2],strcoll(argv[1],argv[2])); printf("strcmp('%s',strcmp(argv[1],argv[2])); return 0; }
注意区别：
$LC_ALL=C ./strcoll_strcmp ' a' '0a'
strcoll(' a','0a'): -16
strcmp(' a','0a'): -16
$LC_ALL=en_US.UTF-8 ./strcoll_strcmp ' a' '0a'
strcoll(' a','0a'): 10
strcmp(' a','0a'): -16
究竟为什么这些比较,我不确定.这必须归功于一些英语词典排序规则.我认为确切的规则在ISO 14651 Method for comparing character strings and description of the common template tailorable ordering和附带的模板表中描述. Glibc在libc / localedata / locales下的源代码树中包含此数据.
