#!/bin/bash #name: upper_to_lower.sh #the function is trun uper to lower #like ABCd to abcd haveuppernumber() {     #test if the string have upper number     str="$(echo $1 | tr '[:upper:]' '[:lower:]')"     if [ "$str" != $1 ] ; then #get some problem         echo "[#have upper number,and i well trun them to lower:#]"         return 1 #have upper number     else         return 0 #no upper number     fi } if [ $# -ne 1 ] ; then     echo "Usage: $0 <string>" >&2     exit 1 fi if ! haveuppernumber $1 ; then #when if is 0 it run? #if [ 0 ] ; then #in shell true return 0 ,false return 1     echo $1 | tr '[:upper:]' '[:lower:]' #it can turn the UPPER number to lower #    echo $1 | tr '[:lower:]' '[:upper:]' #it can turn the lower number to UPPER else     echo "[#no upper number:#]"     echo $1 fi exit 0

#include<stdio.h> #include<stdlib.h> int haveuppernumber(char *p) {     char*q=p;     for(;*q!='\0';q++)     {         if(*q>='A'&&*q<='Z')         {             printf("[#have upper number and i will turn them to lower #]\n");             return 1;         }     }     printf("[#no upper number#]\n");     return 0; } void turntolower(char *p) {     for(;*p != '\0';p++)     {         if(*p>='A' && *p<='Z')         {             *p+=' ';         }     } } int main(int argc , char *argv[]) {     char *p;     p=argv[1];     if(argc != 2)     {         printf("Usage : %s <string>\n",argv[0]);         exit(-1);     }     if(haveuppernumber(p))     {         turntolower(p);         printf("%s\n",argv[1]);     }     else     {         printf("%s\n",argv[1]);     }     return 0; }