使用标准I/O来计算字符数

#include <stdio.h>
#include <stdlib.h> // exit() prototype

int main(int argc, char *argv[])
{
    int ch;         // place to store each character as read
    FILE *fp;       // "file pointer"
    unsigned long count = 0;
    if (argc != 2)
    {
        printf("Usage: %s filename/n", argv[0]);
        exit(EXIT_FAILURE);
    }
    if ((fp = fopen(argv[1], "r")) == NULL)
    {
        printf("Can't open %s/n", argv[1]);
        exit(EXIT_FAILURE);
    }
    while ((ch = getc(fp)) != EOF)
    {
        putc(ch,stdout);  // same as putchar(ch);
        count++;
    }
    fclose(fp);
    printf("File %s has %lu characters/n", argv[1], count);

    return 0;
}