C语言字符串分割

深碍√TFBOYSˉ_ 2023-02-22 07:56 38阅读 0赞

### **                                                         C语言 字符串分割** ###

**一、简述  
        记--字符串分割，strtok()函数的使用例子、自己简单实现split()函数。**

**二、例子代码**

#include <stdio.h>
    #include <string.h>
     
    /*
     * 函数:split
     * 描述:按指定分隔符分割字符串
     * 参数:
     *		str:要分割的字符串
     *		strLen:要分割的字符串的长度
     * 		splitChar:分隔符
     * 		index:获取第几部分, 1<=index
     *		result:结果字符串, result = str[index-1];
     * 		maxLen:指定结果的最大长度
     * 返回值:
     *		>=0:成功, 结果长度
     * 		其它:失败
     * 例子:
     *		split("11;22;33", 8, ';', 2, result. 16);
     *		结果result是:22.
     */
    int split(const char* str, int strLen, const char* splitChar, int index, char* result, int maxLen)
    {
    	int i = 0;
        int ret = 0;	
    	int findLen = 0;
    	int findFlag = 0;	
    	int startIndex = 0;
    	int splitCharLen = 0;
    	
    	//合法性判断
    	if(NULL == str || NULL == result || NULL == splitChar || index<=0)
    	{
    		return -1;
    	}		
    	splitCharLen = strlen(splitChar);
    	findLen = strLen-splitCharLen;
    	if(findLen<0)
    	{
    		return -2;
    	}	
    	
    	//查找结果的左右分隔符位置
    	for(; i<=findLen && str[i] != '\0'; i++)
    	{
    		if(strncmp(&str[i], splitChar, splitCharLen) == 0)
    		{
    			if(0 == findFlag)//find the left
    			{
    				startIndex++;
    				if(1 == index)//第一个直接返回
    				{
    					strncpy(result, &str[0], i);
    					ret = i;
    					break;
    				}
    				else if(startIndex+1 == index)
    				{
    					startIndex = i;
    					findFlag = 1;
    				}
    			}
    			else//find the right
    			{
    				findFlag = 2;
    				break;
    			}
    		}
    	}	
    	
    	//截取结果
    	if(0 != findFlag && startIndex<strLen-1)
    	{
    		startIndex += splitCharLen;
    		ret = i-startIndex;//结果的字符个数
    		if(ret>maxLen || ret>strLen)
    		{
    			ret = 0;
    		}
    		else if(ret>0)
    		{
    			strncpy(result, &str[startIndex], ret);
    			ret = strlen(result);
    		}
    	}
    	return ret;
    }
     
    int main(void)
    {	
    	{
    		const char* splitChar = ";";
    		printf("\n==========strtok1==========\n");
    		char str1[128] = "Keep;learning;and;study;hard";
    		printf("str1:\"%s\", splitChar:\"%s\"\n", str1, splitChar);
    		
    		char* ptr = strtok(str1, splitChar);
    		for(; ptr != NULL; )
    		{
    			printf("%s\n", ptr);
    			ptr = strtok(NULL, splitChar);
    		}
    		printf("strtok after, str1:%s\n", str1);
    		
    		printf("\n==========split1==========\n");
    		char str2[128] = "Keep;learning;and;study;hard";
    		printf("str2:\"%s\", splitChar:\"%s\"\n", str2, splitChar);
    		int i;
    		int ret = 1;
    		char result[128];
    		int strLen = strlen(str2);
    		int resultLen = sizeof(result);
    		for(i=1; ret>0; i++)
    		{
    			memset(result, 0, sizeof(result));
    			ret = split(str2, strLen, splitChar, i, result, resultLen);
    			if(ret>0)
    			{
    				printf("%s\n", result);
    			}
    		}
    		printf("split after, str2:%s\n", str2);
    	}
    	
    	{
    		const char* splitChar = "##";
    		printf("\n==========strtok2==========\n");
    		char str1[128] = "Keep##learning##and##study##hard";
    		printf("str1:\"%s\", splitChar:\"%s\"\n", str1, splitChar);
    		
    		char* ptr = strtok(str1, splitChar);
    		for(; ptr != NULL; )
    		{
    			printf("%s\n", ptr);
    			ptr = strtok(NULL, splitChar);
    		}
    		printf("strtok after, str1:%s\n", str1);
    		
    		printf("\n==========split2==========\n");
    		char str2[128] = "Keep##learning##and##study##hard";
    		printf("str2:\"%s\", splitChar:\"%s\"\n", str2, splitChar);
    		int i;
    		int ret = 1;
    		char result[128];
    		int strLen = strlen(str2);
    		int resultLen = sizeof(result);
    		for(i=1; ret>0; i++)
    		{
    			memset(result, 0, sizeof(result));
    			ret = split(str2, strLen, splitChar, i, result, resultLen);
    			if(ret>0)
    			{
    				printf("%s\n", result);
    			}
    		}
    		printf("split after, str2:%s\n", str2);
    	}
    	return 0;
    }

**三、测试结果**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmZlaWJ1eWk_size_16_color_FFFFFF_t_70][]

![20200715232445699.gif][]

**四、总结  
    strtok()函数介绍**

<table style="width:500px;">  strtok()函数  
 <tbody> 
  <tr> 
   <td style="width:118px;">功能</td> 
   <td colspan="2" style="width:381px;">分割字符串</td> 
  </tr> 
  <tr> 
   <td style="width:118px;">头文件</td> 
   <td colspan="2" style="width:381px;">#include &lt;string.h&gt;</td> 
  </tr> 
  <tr> 
   <td style="width:118px;">原型</td> 
   <td colspan="2" style="width:381px;">char *strtok(char *str, const char *delim);</td> 
  </tr> 
  <tr> 
   <td style="width:118px;">参数</td> 
   <td colspan="2" style="width:381px;"> <p>str：要分割的字符串</p> <p>delim：分隔符</p> </td> 
  </tr> 
  <tr> 
   <td colspan="1" style="width:118px;">返回值</td> 
   <td colspan="2" style="width:381px;">成功：非空指针，分割后的结果字符串</td> 
  </tr> 
  <tr> 
   <td colspan="2" style="width:381px;">失败：NULL，分割后没有得到有效的字符串</td> 
  </tr> 
  <tr> 
   <td style="width:118px;">备注</td> 
   <td style="width:289px;"> <p>第一次调用strtok()时，要解析的字符串应在str中指定。 在每个随后的应解析相同字符串的调用中，str必须置空。</p> <p>即第一次是strtok(str, spplitChar);</p> <p>后面调用strtok(NULL, spplitChar);</p> <p>注意:调用strtok之后会修改原来的str</p> </td> 
   <td>&nbsp;</td> 
  </tr> 
 </tbody> 
</table>

详情请查询man手册，man strtok

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmZlaWJ1eWk_size_16_color_FFFFFF_t_70 1][]

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[20200715232445699.gif]: https://img-blog.csdnimg.cn/20200715232445699.gif
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