The method of C language function returning string

The string pointer is passed in as a function parameter, and the pointer is returned

#include <stdio.h>
#include <string.h>
#include <stdlib.h> 
char * fun(char *p)
{
    
    
    char *eg="STM32";
    strcpy(p,eg);
    return p;
}
int main()
{
    
    
    char *name;   // 或定义char name[20];  定义数组，则不需要利用malloc分配内存空间
    name=(char*)malloc(20);//利用malloc分配内存空间，否则指针未初始化只是一个声明,无法指向有效地址 
    fun(name);
    printf("%s",name);
    free(name);     //使用malloc函数后，必须释放内存空间 
    return 0;
}

Use malloc function to dynamically allocate (note memory release)

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

char* string()
{
    
    
    char *name;
    name=(char *)malloc(20);
    strcpy(name,"Engineer");
    return name;
}

void fun_free(void **p)  //free释放内存后，避免P成为野指针，故将p指向NULL
{
    
    
    free (*p);
    *p=NULL;
    return;
}

int main()
{
    
    
    char* p;
    p=string();
    printf("%s",p);
    fun_free(p);  //进行内存释放，否则会造成内存泄漏
    return 0;
    
}

Return a static local variable static

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

char *changename();
int main()
{
    
    
    char* name1;
    name1=changename();
    printf("%s",name1);
    return 0; 
}

char* changename()
{
    
    
    //使用static定义静态局部变量，防治局部变量在函数返回时，内存释放，数据丢失
    static char name[10];	//初始化数组必须确定存储空间大小
    strcpy(name,"Engineer");
    return name;
}

Use global variables

#include <stdio.h>
#include <string.h>

char buf[10];
void fun(void)
{
    
    
    strcpy(buf,"ABCDEF");
}
int main()
{
    
    
    fun();
    printf("%s",buf);
}

strcpy function usage

 char *strcpy(char *dest, const char *src)  //把src所只想的字符串复制到dest中

• Parameter
  dest: the target array or pointer to store the string (memory space must be allocated)
  src: the string to be copied
• Return value
  This function returns a pointer to the target string dest that has completed the assignment.

#include <stdio.h>
#include <string.h>
#include <stdlib.h> 

int main()
{
    
    
    char *name;
//  char name[20];  //定义一个数组，比指针分配内存空间简单
    char *p="STM32F103RCT6";
    name=(char*)malloc(20);  //利用malloc分配内存空间，否则指针未初始化时只是一个声明
    
    strcpy(name,p);
    printf("%s",name);
    free(name);     //释放内存空间 
    return 0;
}

Reference link