C风格字符串
C风格字符串
如下示例代码，c文件，
//
// sub1.c
// HelloWorld
//
// Created by Yale Li on 15/10/3.
// Copyright © 2015年 Yale Li. All rights reserved.
//
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
void travel_str(){
char x = 0x21; //字符 !
while (x<=0x7e) {
printf("%x is %c\n",x,x);
x++;
}
}
void test_c_style_str(){
//创建五个字符大小的内存空间，并返回首地址
char *start = malloc(5);
*start = 'L';
*(start + 1) = 'o';
*(start + 2) = 'v';
*(start + 3) = 'e';
*(start + 4) = '\0';
// 指针的下标运算
// start[0] = 'L';
// start[1] = 'o';
// start[2] = 'v';
// start[3] = 'e';
// start[4] = '\0';
printf("%s has %zu characters\n",start,strlen(start));
printf("the third letter is %c\n",*(start + 2));
free(start);
start = NULL;
return;
}
//分配连续内存地址空间
void test_malloc(){
//分配3个float大小的内存地址空间，并返回首地址
float *start = malloc(3 * sizeof(float));
start[0] = 1.2;
start[1] = 1.3;
start[2] = 1.4;
for (int i = 0; i<3; i++) {
printf("the value is %f\n",start[i]);
}
free(start);
start = NULL;
}
//字符串的字面量
void test_string_literal(){
const char *start = "Love"; //直接定义字符串字面量
while (*start!='\0') {
printf("%x is %c\n",*start,*start);
start++;
}
}
//定义字符数组
//在程序中往往依靠检测'\0'的位置来判定字符串是否结束，而不是根据数组的长度来决定字符串长度
void test_char_array(){
//指定字符数组的长度是10，但是只初始化了其中的前9个数组元素，最后一个自动初始化为空字符，即'\0'
//字符数组的长度为10，但是字符串的长度为9，结束符不算进字符串的长度
const char str1[10] = {'c',' ','p','r','o','g','r','a','m'};
printf("the 10th letter is %x\n",str1[9]);
const char *p1 = str1;
while (*p1!='\0') {
printf("%c",*p1);
p1++;
}
printf("\n");
//显示指定了结束符，算上结束符，数组的长度为10，但是字符串的长度为9，字符串的长度不包括结束符
const char str2[10] = {'c',' ','p','r','o','g','r','a','m','\0'};
const char *p2 = str2;
while (*p2!='\0') {
printf("%c",*p2);
p2++;
}
printf("\n");
//其余的自动初始化为空字符，即'\0'，也可以显示的指定字符串的结束符
char str3[10] = {'h','a','p','p','y'};
char *p3 = str3;
while (*p3!='\0') {
printf("%c",*p3);
p3++;
}
printf("\n");
char str4[5] = {'h','a','p','p','y'}; //数组长度为5，没有结束符
printf("the str4 value is %s\n",str4);
char str5[6] = {'h','a','p','p','y','\0'};//包含结束符在内的数组长度为6
//初始化字符数组时，不指定数组的长度
//同时没有指定字符串结束符
//这里数组的长度为7，而字符串的长度由于没有字符串结束符而不确定
char str6[] = {'c','h','i','n','e','s','e'};
for (int i = 0; i<strlen(str6); i++) {
printf("%c",str6[i]);
}
printf("\n");
//初始化字符数组时，不指定数组的长度
//指定字符串结束符
//这里数组的长度为8，同时字符串的长度为7
char str7[] = {'c','h','i','n','e','s','e','\0'};
for (int i = 0; i<strlen(str7); i++) {
printf("%c",str7[i]);
}
printf("\n");
//用字符串常量来初始化字符数组
//编译器会自动加上字符串结束符
char str8[] = {"welcome1"};
for (int i = 0; i<strlen(str8); i++) {
printf("%c",str8[i]);
}
printf("\n");
//用字符串常量来初始化字符数组，可以去掉花括号
//这种方式初始化字符数组会自动加上字符结束符
char str9[] = "welcome2";
for (int i = 0; i<strlen(str9); i++) {
printf("%c",str9[i]);
}
printf("\n");
//用字符串常量来初始化字符数组，可以去掉花括号
//使用字符串常量初始化字符数组时，指定了长度，该长度不包含字符串结束符
//数组的长度是一定的，而字符串的长度不确定
char str10[8] = "welcome3";
for (int i = 0; i<strlen(str10); i++) {
printf("%c",str10[i]);
}
printf("\n");
printf("the length of str1 is %ld\n",strlen(str1));
printf("the length of str2 is %ld\n",strlen(str2));
printf("the length of str3 is %ld\n",strlen(str3));
printf("the length of str4 is %ld\n",strlen(str4));
printf("the length of str5 is %ld\n",strlen(str5));
printf("the length of str6 is %ld\n",strlen(str6));
printf("the length of str7 is %ld\n",strlen(str7));
printf("the length of str8 is %ld\n",strlen(str8));
printf("the length of str9 is %ld\n",strlen(str9));
printf("the length of str10 is %ld\n",strlen(str10));
printf("\n");
}
//字符串数组
void test_char_pointer_array(){
//定义一个字符串数组
char *strs[5] = { "CHINA","AMERICA","AUSTRALIA","FRANCE","GERMAN"};
//遍历字符串数组
for (int i=0;i<5;i++){
printf("%s\n",strs[i]);
}
}
main文件，
#include <stdio.h>
extern void travel_str();
extern void test_c_style_str();
extern void test_malloc();
extern void test_string_literal();
extern void test_char_array();
extern void test_char_pointer_array();
int main(int argc, const char * argv[]){
travel_str();
test_c_style_str();
test_malloc();
test_string_literal();
test_char_array();
test_char_pointer_array();
return 0;
}
输出打印，只贴出字符串长度的打印，
the length of str1 is 9
the length of str2 is 9
the length of str3 is 5
the length of str4 is 11
the length of str5 is 5
the length of str6 is 12
the length of str7 is 7
the length of str8 is 8
the length of str9 is 8
the length of str10 is 16
=====END=====