程序清单13.2 reduto.c

/* come from <C Primer Plus> * 程序清单13.2 reduto.c * 把文件压缩为原来的1/3 * 注意: main参数可以在IDE的Parameters栏中设置,每个参数对应一个字符串,多个参数之间用空格分开. */
#include <stdio.h>
#include <stdlib.h> // for exit()
#include <string.h> // for strcpy(), strcat()
#define LEN 40
int main(int argc, char *argv[])
{
    
	FILE *in, *out;
	int ch;
	char name[LEN];
	int count = 0;
// 检查命令行参数
	if (argc < 2)
	{
    
		fprintf(stderr, "Usage: %s filename\n", argv[0]);
		exit(1);
	}
// set up input
	if ((in = fopen(argv[1], "r")) == NULL)
	{
    
		fprintf(stderr, "I couldn't open the file \"%s\"\n", argv[1]);
		exit(2);
	}
// set up output
	strcpy(name, argv[1]); // copy filename
	strcat(name, ".red");            // append .red
	if ((out = fopen(name, "w")) == NULL)
	{
                           // open file for writing
		fprintf(stderr, "Can't create output file.\n");
		exit(3);
	}
// copy data
	while ((ch = getc(in)) != EOF)
		if (count++ % 3 == 0)
			putc(ch, out);  // print every 3rd char
// clean up
	if (fclose(in) != 0 || fclose(out) != 0)
		fprintf(stderr, "Error in closing files\n");
	return 0;
}