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Strcat () - connection string

2022-07-21 05:58:00 【InfoQ】

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strcat() - Connection string

strcat() The function is declared as follows

char *strcat(char *dest, const char *src)
Append a copy of the source string to the destination string .
dest
 → Point to target array , The array contains a C character string , And enough to hold the appended string .
src
 →  Point to the string to append , The string does not override the target string .
This function returns a string pointing to the final destination
dest
The pointer to .
hold  
src
  The string pointed to is appended to  
dest
  The end of the string that you are pointing to .
You can't add programs to yourself , like this ：

char arr[20] = &quot;Cyuyan&quot;
strcat(arr,arr);
printf(&quot;%s\n&quot;,arr);

It won't work like this , Originally, my array stored ：Cyuyan\0, Because this space is long enough, there is still content behind it . So if we want to add, it will be like this ：CyuyanCyuyan, In essence, our slash 0 Will be in CyuyanCyuyan This string n Behind . But slashes 0 It is covered. , So who covered it , Is added by oneself arr Covered by . This will form a cycle , Because we'll never find the backslash 0－O－

strcat() Function code example

Use
strcat()
The function code example is as follows

#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
#include<string.h>
int main(void)
{
 char arr1[20] = &quot;hello C&quot;;
 char arr2[20] = &quot;yuyan&quot;;
 strcat(arr1, arr2);
 printf(&quot;arr1 = %s\n&quot;, arr1);
 return 0;
}

The operation results are as follows
arr1 = hello Cyuyan
Let's take a look at the steps of its debugging results 🧐

null

Create a custom function implementation strcat() The function of

The idea is very simple. In fact
Ⅰ→dest Find the target string '\0'
Ⅱ→ Then append the source data to the string '\0' Behind , Be careful ： Is included '\0' Of
The sample code is as follows ：

#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
#include<assert.h>
char *My_strcat(char *dest, const char *src)
{
 assert(dest && src != NULL);// Assertion 
 char *ret = dest;
 while (*dest != '\0')//'\0' Of ASCLL The code value is 0
 {
 dest++;
 }
 //dest Pointing to '\0'
 while (*dest++ = *src++)
 {
 ;
 }
 /* amount to 
 while (*src != '\0')
 {
 *dest++ = *src++;
 }*/
 return ret;
}
int main(void)
{
 char arr1[20] = &quot;hello C&quot;;
 char arr2[20] = &quot;yuyan&quot;;
 printf(&quot;%s\n&quot;, My_strcat(arr1, arr2));
 return 0;
}

The operation results are as follows
hello Cyuyan

null

⒈ notes →
There are many details in the above code, which is worth debugging. Here are the running steps . Such as
⒉ notes →'\0' In fact, it also corresponds to C Empty character of language NULL Decimal system 0 Value .

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