上篇对嵌入式中C语言基本数据类型，关键字和常用操作进行了汇总，这篇我们将侧重字符串操作。请看下面的字符串处理函数：
a.库函数
1)将字符串src拷贝到字符数组dest内
char *strcpy(char *dest, const char *src);
dest 要输入的字符数组名,内存的地址
src 要复制的字符数组名,内存地址
/*************************************************************************
> File Name: strcpy_test.c
> Author: shuk
> Mail: wsksec@gmail.com
> Created Time: Fri 31 Jul 2015 04:29:07 PM CST
************************************************************************/ #include <stdio.h>
#include <string.h> int main(void)
{
char str[]="asdfjkladfeifdfjkjfljfljlasjf";
char dest[BUFSIZ]="";
char ch[] = "ab";
strcpy(dest,str);
printf("dest = %s\n",dest);
printf("sizeof(ch) = %ld\n",sizeof(ch));//include \0
return ;
}
2)求字符串长度
size_t strlen(const char *s);
字符串长度:是'\0'前面的字母个数,不包含'\0'
s 要计算长度的字符串,或存字符串内存的地址
/*************************************************************************
> File Name: strlen_test.c
> Author: shuk
> Mail: wsksec@gmail.com
> Created Time: Fri 31 Jul 2015 06:35:25 PM CST
************************************************************************/ #include <stdio.h>
#include <string.h> int main(void)
{
char str[] = "qwertyuasdfgj";
int len;
len = strlen(str);
printf("strlen(str) = %d,%s\n",len,str);//not inlcude \0
return ;
}
3)比较字符串的大小
int strcmp(const char *s1, const char *s2);
s1,s2,是两个要比较的字符串
返回的值 <0 代表s1小,=0 相等 >0 s1大
/*************************************************************************
> File Name: strcmp_test.c
> Author: shuk
> Mail: wsksec@gmail.com
> Created Time: Fri 31 Jul 2015 06:58:19 PM CST
************************************************************************/ #include <stdio.h>
#include <string.h> int main(void)
{
char *str = "adfndfkkf";
char *dest = "acdffgf"; if(strcmp(dest,str) == )
{
printf("str == dest\n");
}
else if(strcmp(dest,str) < )
{
printf("dest < str\n");
}
else
{
printf("dest > str\n");
} return ;
}
4)字符串拼接
char *strcat(char *dest, const char *src);
dest 目标的地址,目标的字符数组
src 源地址,是将src字符串连接在dest字符串后面
/*************************************************************************
> File Name: strcat_test.c
> Author: shuk
> Mail: wsksec@gmail.com
> Created Time: Fri 31 Jul 2015 07:14:01 PM CST
************************************************************************/ #include <stdio.h>
#include <string.h> int main(void)
{
char *str = "abcdefg";
char dest[BUFSIZ] = "higklmn"; printf("strlen(str) == %d\n",strlen(str));
printf("strlen(dest) == %d\n",strlen(dest));
strcat(dest,str);
printf("String cating. . .\n");
sleep();
printf("dest == %s\n",dest);
printf("strlen(dest) == %d\n",strlen(dest));
printf("sizeof(dest) == %d\n",sizeof(dest));
return ;
}
5)在字符串中查找另一个字符串
char *strstr(const char *haystack, const char *needle);
haystack 一个字符串
needle 要寻找字符串,在haystack里面查找needle这个字符串
返回值,是在haystack内找到的字符串的地址或者说,是找到的字符数组
/*************************************************************************
> File Name: strstr_test.c
> Author: shuk
> Mail: wsksec@gmail.com
> Created Time: Fri 31 Jul 2015 07:32:36 PM CST
************************************************************************/ #include <stdio.h>
#include <string.h> int main(void)
{
char *haystack = "abcdadecdakllgd";
char *needle = "b";
char *temp; temp = strstr(haystack,needle);
printf("temp == %s\n",temp);
return ;
}
6)从键盘上获取字符串
char *gets(char *s);
s 准备好的字符数组,或内存地址
见 7)demo
7)将字符串输出到屏幕
int puts(const char *s);
s 是要输出的字符数组,或内存地址
/*************************************************************************
> File Name: gets_test.c
> Author: shuk
> Mail: wsksec@gmail.com
> Created Time: Fri 31 Jul 2015 07:50:02 PM CST
************************************************************************/ #include <stdio.h>
#include <string.h> int main(void)
{
char str[] = ""; gets(str);
// printf("str == %s\n",str);
puts(str);
return ;
}
8)将字符串按格式写入到内存,或字符数组内
sprintf(char *str,"格式字符串",参数列表....);
str 是准备好的字符数组
格式字符串 由%c %d %lf %f %u等组成的字符串
char str1[256]="";
int a=102;
sprintf(str1,"a=%d, &a=%p, ASCII = %c\n",a,&a,a);
puts(str1);
用途:将数值转换为字符串
/*************************************************************************
> File Name: sprint_test.c
> Author: shuk
> Mail: wsksec@gmail.com
> Created Time: Fri 31 Jul 2015 09:16:36 PM CST
************************************************************************/ #include <stdio.h> int main(void)
{
char str[] = "";
int a = ; sprintf(str,"a = %d,&a = %p,ascii = %c",a,&a,a);
// printf("str = %s\n",str);
puts(str);
return ;
}
9)把字符串转换为整数
#include <stdlib.h>
int atoi(const char *nptr); 把字符串转换为整型
long atol(const char *nptr); 转换为长整型
double atof(const char *nptr);转换为浮点
/*************************************************************************
> File Name: atoi_test.c
> Author: shuk
> Mail: wsksec@gmail.com
> Created Time: Fri 31 Jul 2015 09:29:20 PM CST
************************************************************************/ #include <stdio.h>
#include <string.h>
#include <stdlib.h> int main(void)
{
char *str = ""; //if str[] = "abc",after atoi,temp == 0
int temp; temp = atoi(str);
printf("temp == %d\n",temp);
return ;
}
b.自定义的字符串处理函数
当涉及到对字符串操作是，一定要记得这几点：
a)若要存储字符串，声明的变量必须指定空间大小，必要是要对其初始化。如 char [256] = "";char *str = "abdefg";
b)操作函数中的参数要用 const 关键子限定，防止外部对存储空间地址进行修改；
1)strcpy_me
/*************************************************************************
> File Name: strcpy_me.c
> Author: shuk
> Mail: wsksec@gmail.com
> Created Time: Sat 01 Aug 2015 03:00:08 PM CST
************************************************************************/ #include <stdio.h>
#include <string.h> char *fun_cpy(char *,const char *); int main(void)
{
char *str = "abcdefghikjlmnopqrstuswxyz";
char dest[] = "";
dest[] = 'v'; fun_cpy(dest,str);
printf("dest:%s\n",dest);
printf("str :%s\n",str);
return ;
} char *fun_cpy(char *dest,const char *str)
{
int i = ;
while(*(str + i) != '\0')
{
*(dest++) = *(str + i);
i++;
}
*dest = '\0';
return dest;
}
2)strlen_me
/*************************************************************************
> File Name: strlen_me.c
> Author: shuk
> Mail: wsksec@gmail.com
> Created Time: Sat 01 Aug 2015 03:26:22 PM CST
************************************************************************/ #include <stdio.h>
#include <string.h> int my_strlen(const char *); int main(void)
{
char *str = "abcdefg";
int val; val = my_strlen(str);
printf("val == %d\n",val);
return ;
} int my_strlen(const char *s)
{
int i = ; while(*(s+i) != '\0')
{
i++;
}
return i;
}
3)strcat_me
/*************************************************************************
> File Name: strcat_me.c
> Author: shuk
> Mail: wsksec@gmail.com
> Created Time: Sat 01 Aug 2015 04:00:37 PM CST
************************************************************************/ #include <stdio.h>
#include <string.h> void my_strcat(char *,const char *); int main(void)
{
char *str = "abcdefg";
char dest[] = "higklmnl"; my_strcat(dest,str);
printf("str:%s\n",str);
printf("dest:%s\n",dest);
return ;
} void my_strcat(char *dest,const char *str)
{
int i; while(*dest++)
;
dest -= ;
while(*(str+i) != '\0')
{
*dest++ = *(str+i);
i++;
}
*dest = '\0';
}
4)strcmp_me
/*************************************************************************
> File Name: strcmp_me.c
> Author: shuk
> Mail: wsksec@gmail.com
> Created Time: Sat 01 Aug 2015 04:12:51 PM CST
************************************************************************/ #include <stdio.h>
#include <string.h> int my_strcmp(const char *,const char *); int main(void)
{
char *str = "abcdefgbra";
char *dest = "abcdefgbaa";
int i; i = my_strcmp(dest,str);
if(i > )
{
printf("dest > str\n");
}
else if(i < )
{
printf("dest < str\n");
}
else
{
printf("dest = str\n");
} return ;
} int my_strcmp(const char *dest,const char *str)
{
int i = ; while()
{
if((*(dest + i) == *(str + i)) && (*(dest + i)!='\0'))
{
i++;
}
else if(*(dest + i) > *(str + i))
{
return ;
}
else if(*(dest + i) < *(str + i))
{
return -;
}
else
{
return ;
}
}
}
细节不足的地方请您指教，后续我也会加以说明和修改。