C的文件扩展名作为用户输入

Question

I have a save as function and I need my program to recognise and separate the file name from the file extension. I have read Extracting the extension of a file but my save as function is not main, so I can not have argv[1]. Here is my full code so far:

#include <stdio.h>
#include <errno.h>

void save_as()
{
    // user enters their desired name for the file
    char filename;
    char fileext;
    printf("Filename:\t");
    scanf("%s", &filename);
    filename = strtok(filename, "."); // according to the link I mentioned above this should have been: filename = strtok(argv[1], ".");
    fileext = strtok(NULL, ".");
}

int main()
{
    save_as();
    return 0;
}

Answer 1

Following lines are correct:

char filename;
char fileext;
printf("Filename:\t");
scanf("%s", &filename);
filename = strtok(filename, ".");
fileext = strtok(NULL, ".");

however strtok returns char* and you have declared filename and fileext as single char . Also note that there should be memory associated with the filename buffer. Change it to:

char filename[255];
printf("Filename:\t");
scanf("%254s", &filename);
filename = strtok(filename, ".");
char* fileext = strtok(NULL, ".");

Also consider checking the return value of these calls as some error might occur.

Answer 2

You can have argv[1]:

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

void save_as(char *filename)
{
    // user enters their desired name for the file
    char *fileext;

    filename = strtok(filename, "."); // according to the question I mentioned above this should have been: filename = strtok(argv[1], ".");
    fileext = strtok(NULL, ".");
}

int main(int argc, char **argv)
{
    if(argc != 2)
    {
       printf("usage: myprogram myfile.myextension");
       return 0;
    }
    save_as(argv[1]);

    return 0;
}