C ++ (5) access function to determine whether a file exists

Recently, I saw a function. At first glance, I thought it was very sb, because the definition of remove is inside the if, and it becomes a local variable. The result is if the file "234. bin "if it does not exist, an error will occur, because the lifecycle of the remove operation is limited.

As a result, my eyes are highlighted:

#include<iostream>#include "unistd.h"#include "stdio.h"#include "stdlib.h"using namespace std;int main(){      if(access("234.bin",F_OK))    {       bool remove=true;    }    if(remove)    {        cout<<"Need to delete..."<<endl;    }    return 0;}

As a result, no matter whether the file exists or not:

In fact, I personally think this problem lies in the return value of this access function. Its return value is

0 if the file is in the specified mode

-1 if an error occurs

Therefore, whether the above program finds the file (0) or cannot find (-1), it is false, so it should never enter if (remove ..

So it should be:

if(0 == access("234.bin",F_OK)){remove = true;}

After this change, I still cannot see the error I want. I want to see the error that does not exist in remove ~~ Unfortunately, it is still:

Originally:

Remove is an existing function. The function address is not empty, so you can always enter if (remove ){}

You can use the following code to determine whether a file exists:

#include<iostream>#include "unistd.h"#include "stdio.h"#include "stdlib.h"using namespace std;int file_exist(char *file){    return (access(file,F_OK) == 0);}int main(){    cout<<"Does file exist :"<<(file_exist("234.bin")?"Yes":"No")<<endl;    return 0;}

Summary:

(1) Use the access function to note that the returned values are 0 and-1, both of which are false.

(2) remove is a function name. Do not use the system stuff when defining the name.