C学习笔记——打开文件，并保存错误信息

        这两天学习文件访问，产生了一个做个小程序的想法：打开一个文件，并把它的内容显示在屏幕上，如果不能打开，则记录当前时间和错误信息到错误文件中。

        运行时，把文件放入在cmd默认的目录（我这是C:\Users\Ralap）下，通过命令窗口（cmd）来控制。这把文件名命名为“OpenFile.exe”，在输入命令的时候，

        输入格式为：程序文件名     【需打开的文件名1】    【需打开的文件名2】……

        运行效果如下：

        总体思路为：

        1、通过命令后面的参数，打开文件。能打开便显示，无法打开便把错误信息输入到err.txt中

        2、处理里命令后面的参数后，再次询问是否需要打开其他文件。打开成功与否的处理与上面一样

        代码如下：

#include <stdio.h>
#include <conio.h>
#include <string.h>
#include <stdlib.h>
#include <time.h>
#include <ctype.h>
#include <direct.h>	//get the current working directroy: getcwd()

#define FILE_NAME_SIZE 50
#define ERR_INFO_SIZE 100
#define READ "r"
#define WRITE "w"
#define ADD "a"
#define ERR_HANDLE_FILE "err.txt"

char printFile(FILE *ifp, FILE *ofp)
{
	char c;
	while((c=getc(ifp)) != EOF)
		putc(c,ofp);
	return ferror(ofp) ? EOF : 1;
}
void errorHandle(char *errfname,char *s)
{
	time_t dtime;
	FILE *errp;
	if((errp=fopen(errfname,ADD)) == NULL)
	{
		fprintf(stderr,"Error_handle file \"%s\" can't operated!",errfname);
		exit(1);	//exit the program directly
	}
	else{
		dtime=time(NULL);	//get the time of the now
		fprintf(errp,"%s%s\n\n",ctime(&dtime),s);
		fclose(errp);
	}
}
/*stradd: stack the strings*/
char stradd(char *destination, unsigned size, char *first, char *second, char *third)
{ /*若不判断长度，总长度过长会导致fname指针无效，在释放内存时将出现异常，中断在此函数CheckBytes()*/
	if(size <= strlen(first)+strlen(second)+strlen(third))
		return EOF;
	strcpy(destination,first);
	strcat(destination,second);
	strcat(destination,third);
	return 0;
}

int main(int argc, char **argv)
{
	char fpath[80];	//the path of this file
	FILE *fp;
	char *exe;
	char slct;
	char *fname;
	char errinfo[ERR_INFO_SIZE];

	exe=strrchr(*argv, '\\') == NULL ? *argv : (strrchr(*argv, '\\')+1);
	puts("********************************************************************");
	puts("***The function of this file is open a file which you want,      ***");
	puts("***and the error information will output to a error_handle file, ***");
	puts("***like err.txt                                                  ***");
	puts("********************************************************************");
	if(getcwd(fpath,sizeof(fpath)) == NULL)	//print current working directory
		puts("Error: Can't get current working directory\n");
	else
		printf("Current working directory is:\n%s\n",fpath);
	puts("____________________________________________________________________");

	while(--argc >0){
		if((fp = fopen(*++argv, "r")) == NULL){
			stradd(errinfo, ERR_INFO_SIZE, exe," can't open the file: ",*argv);
			errorHandle(ERR_HANDLE_FILE,errinfo);
			fprintf(stderr,"%s\n",errinfo);
			continue;
		}
		printf("The file \"%s\" opened successfully, and the following is its contents:\n",*argv);
		printFile(fp,stdout);
		puts("\n");
		fclose(fp);
	}
	while(1){	//ask users whether they want to open other files until they select "N".
		printf("Do you wanta open other files?(Y or N):");
		scanf("%c",&slct);
		while(getchar() != '\n'); //empty the stdin
		slct=toupper(slct);
		if(slct == 'N') break;
		if(slct == 'Y'){
			printf("Please input the file name:");
			fname =(char *)malloc(sizeof(*fname)*FILE_NAME_SIZE);
			scanf("%s",fname);
			while(getchar() != '\n'); //empty the stdin
			if((fp = fopen(fname,"r")) == NULL){
				if(stradd(errinfo, ERR_INFO_SIZE, exe, " can't open the file: ", fname) == EOF){
					puts("your path is too deep, or the length of the path is too long");break;
				}
				errorHandle(ERR_HANDLE_FILE,errinfo);
				fprintf(stderr,"%s\n",errinfo);
			}
			else{
				printf("The file \"%s\" opened successfully, and the following is its contents:\n",fname);
				printFile(fp,stdout);
				puts("");	//auto change line
				fclose(fp);
			}
			free(fname);
		}
	}

	puts("");
	system("pause");
}