字符函数和字符串函数(上)-C语言详解

CSDN的各位友友们你们好,今天千泽为大家带来的是C语言中字符函数和字符串函数的详解,掌握了这些内容能够让我们更加灵活的运用字符串,
接下来让我们一起走进今天的内容吧!
写这篇文章需要在cplusplus.com上大量截图,十分不易!
如果对您有帮助的话希望能够得到您的支持和帮助,我会持续更新的!

0.前言

C语言中对字符和字符串的处理很是频繁，但是C语言本身是没有字符串类型的，字符串通常放在

常量字符串中或者字符数组中。

字符串常量适用于那些对它不做修改的字符串函数.

首先,我们将本次要介绍的函数分一下类

长度不受限制的字符串函数

strcpy

strcat

strcmp

长度受限制的字符串函数介绍

strncpy

strncat

strncmp

1.函数介绍

🚀strcpy

例子

/* strcpy example */
#include <stdio.h>
#include <string.h>int main ()
{char str1[]="Sample string";char str2[40];char str3[40];strcpy (str2,str1);strcpy (str3,"copy successful");printf ("str1: %s\nstr2: %s\nstr3: %s\n",str1,str2,str3);return 0;
}

输出：

str1: Sample string
str2: Sample string
str3: copy successful

🚩模拟实现strcpy

#include<stdio.h>
#include<string.h>
//1.参数顺序
//2.函数的功能，停止条件
//3.assert
//4.const修饰指针
//5.函数返回值
//6.题目出自《高质量C/C++编程》书籍最后的试题部分
//返回的是目标空间的起始地址
#include<assert.h>
char * my_strcpy(char * dest, const char* src)
{char * ret = dest;assert(dest!=NULL);assert(src != NULL);while ((*dest++ = *src++)){;}return ret;
}
int main()
{char arr1[] = "hehe";char arr2[20] = { 0 };my_strcpy(arr2, arr1);printf("%s\n", arr2);return 0;
}

友友们记得动手实践!!!

🚀strcat

官方例子

/* strcat example */
#include <stdio.h>
#include <string.h>int main ()
{char str[80];strcpy (str,"these ");strcat (str,"strings ");strcat (str,"are ");strcat (str,"concatenated.");puts (str);return 0;
}

输出

these strings are concatenated.

🚩模拟实现strcat

#include<stdio.h>
#include<assert.h>
char* my_strcat(char* dest, const char* src)
{char* ret = dest;assert(dest != NULL);assert(src != NULL);//找目标空间的\0while (*dest!='\0'){dest++;}//拷贝while ((*dest++ = *src++)){;}return ret;
}
int main()
{char arr1[20] = "hello ";char arr2[] = "world";//追加my_strcat(arr1, arr2);printf("%s\n", arr1);return 0;
}

🚀strcmp

官方例子

#include <stdio.h>
#include <string.h>int main ()
{char key[] = "apple";char buffer[80];do {printf ("Guess my favorite fruit? ");fflush (stdout);scanf ("%79s",buffer);} while (strcmp (key,buffer) != 0);puts ("Correct answer!");return 0;
}

输出

Guess my favourite fruit? orange
Guess my favourite fruit? apple
Correct answer!

🚩模拟实现strcmp

#include<stdio.h>
#include<string.h>
#include<assert.h>
int my_strcmp(const char* str1, const char* str2)
{assert(str1 != NULL);assert(str2 != NULL);while (*str1 == *str2){if (*str1 == '\0'){return 0;}str1++;str2++;}if (*str1 > *str2){return 1;}else{return -1;}
}int main()
{char arr1[] = "abcdef";char arr2[] = "bbcdef";int ret = my_strcmp(arr1, arr2);printf("%d\n", ret);return 0;
}

🚀strncpy

官方例子

/* strncpy example */
#include <stdio.h>
#include <string.h>int main ()
{char str1[]= "To be or not to be";char str2[40];char str3[40];/* copy to sized buffer (overflow safe): */strncpy ( str2, str1, sizeof(str2) );/* partial copy (only 5 chars): */strncpy ( str3, str2, 5 );str3[5] = '\0';   /* null character manually added */puts (str1);puts (str2);puts (str3);return 0;
}

输出

To be or not to be To be or not to be To be

🚩模拟实现strncpy

#include<stdio.h>
#include<string.h>
#include<assert.h>
int main()
{char arr1[] = "abcdef";char arr2[5] = { 0 };strncpy(arr2, arr1, 3);printf("%s\n", arr2);return 0;
}

🚀strncat

官方例子

/* strncat example */
#include <stdio.h>
#include <string.h>int main ()
{char str1[20];char str2[20];strcpy (str1,"To be ");strcpy (str2,"or not to be");strncat (str1, str2, 6);puts (str1);return 0;
}

输出

To be or not

🚩模拟实现strncat

#include<stdio.h>
#include<string.h>
#include<assert.h>
int main()
{char arr1[20] = "hello \0xxxxxxxx";char arr2[] = "world";strncat(arr1, arr2, 3);printf("%s\n", arr1);return 0;
}

🚀strncmp

官方例子

/* strncmp example */
#include <stdio.h>
#include <string.h>int main ()
{char str[][5] = { "R2D2" , "C3PO" , "R2A6" };int n;puts ("Looking for R2 astromech droids...");for (n=0 ; n<3 ; n++)if (strncmp (str[n],"R2xx",2) == 0){printf ("found %s\n",str[n]);}return 0;
}

输出

Looking for R2 astromech droids... found R2D2 found R2A6

🚩模拟实现strncmp

#include<stdio.h>
#include<string.h>
#include<assert.h>
int main()
{char arr1[] = "abcdef";char arr2[] = "abcq";int ret = strncmp(arr1, arr2, 4);printf("%d\n", ret);return 0;
}

好了,今天的分享暂时告一段落,预知后续请看下篇😁,祝大家学习进步!