[Linux] undefined reference to `itoa’

I wrote a simple C program in Linux, which used Itoa. But when compiling, I prompted “undefined reference to ` Itoa ‘”, I thought it would be OK to add – LC, but the result was the same. Internet found that some people say that this function does not exist in Linux, generally use sprintf to replace. Look at the following code and comments:

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

int num = 0;
char namebuf[100];
char prefix[] = "/tmp/tmp/p";

char* gentemp()
{
    int length, pid;

    pid = getpid();
    strcpy(namebuf, prefix);
    length = strlen(namebuf);
    //itoa(pid, &namebuf[length], 10);      // Unix version: itoa() does not exist in the header file <stdlib.h>
    sprintf(namebuf+length, "%d", pid); // use sprintf to convert integers to strings
    strcat(namebuf, ".");
    length = strlen(namebuf);
    printf("before do...while\n");
    char command[1024] = {0};
    do 
    {
        //itoa(num++, &namebuf[length], 10);
        sprintf(namebuf+length, "%d", num++);
        sprintf(command, "touch %s", namebuf);  // Creating files via touch
        system(command);
        printf("command = %s, namebuf[%d]=%d\n", command, num-1, num-1);
    } while (num < 50 && access(namebuf, 0) != -1); // access to determine whether a file exists
    printf("end of do...while\n");

    return namebuf;
}

int main( void )
{
    char *p = gentemp();
    printf("%s\n", p);

    return 0;
}

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