fstream的用法总结

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#include <iostream>#include <fstream>#include <string>using namespace std;void each_line(const char* in, const char* out);void each_word(const char* in, const char* out);void each_char(const char* in, const char* out);int main(){    const char *path_in  = "D:\\project\\cpp\\file\\input";    const char *path_out_line = "D:\\project\\cpp\\file\\output_each_line";    const char *path_out_word = "D:\\project\\cpp\\file\\output_each_word";    const char *path_out_char = "D:\\project\\cpp\\file\\output_each_char";    //ifstream infile(path_in);    //ifstream infile;    //infile.open(path_in, istream::in);    //ofstream outfile(path_out);    //ofstream outfile;    //outfile.open(path_out, ofstream::out);    each_line(path_in, path_out_line);    each_word(path_in, path_out_word);    each_char(path_in, path_out_char);    return 0;}void each_line(const char* in, const char* out){    ifstream infile(in);    ofstream outfile(out);    string s;    if(infile){        while(getline (infile, s)){            cout<<s<<endl;            outfile<<s<<endl;        }    }else{        cout<<"empty file!"<<endl;    }    infile.close();    outfile.close();}void each_word(const char* in, const char* out){    ifstream infile(in);    ofstream outfile(out);    string s;    if(infile){        while(infile >> s){            cout<<s<<endl;            outfile<<s<<endl;        }    }else{        cout<<"empty file!"<<endl;    }    infile.close();    outfile.close();}void each_char(const char* in, const char* out){    ifstream infile(in);    ofstream outfile(out);    char s;    if(infile){        while((s = infile.get()) != EOF){            cout<<s<<endl;            outfile<<s<<endl;        }    }else{        cout<<"empty file!"<<endl;    }    infile.close();    outfile.close();}

注意点：

1，两种打开方式有两种，

一种是：

const char *path_in = "D:\\project\\cpp\\file\\input";

ifstream infile(path_in); // =file.open("D:\\project\\cpp\\file\\input",ios::in|ios::out);

第二种是：

const char *path_in = "D:\\project\\cpp\\file\\input";

ifstream infile;
infile.open(path_in, istream::in);

打开方式：

ios::app：　　　以追加的方式打开文件
ios::ate：　　　文件打开后定位到文件尾，ios:app就包含有此属性
ios::binary：　以二进制方式打开文件，缺省的方式是文本方式。两种方式的区别见前文
ios::in：　　　文件以输入方式打开（文件数据输入到内存）
ios::out：　　　文件以输出方式打开（内存数据输出到文件）
ios::nocreate：不建立文件，所以文件不存在时打开失败
ios::noreplace：不覆盖文件，所以打开文件时如果文件存在失败
ios::trunc：　　如果文件存在，把文件长度设为0

2，文件遍历的三种方式：

while(getline (infile, s)) //line

while(infile >> s) //word

while((s = infile.get()) != EOF) //char

参考：

1，http://www.cnblogs.com/kevin2010_vip/archive/2010/02/03/1662853.html

2，http://panpan.blog.51cto.com/489034/101625/

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