[cpp]: <fstream> - read_from

[cpp]: <fstream> - read_from_file

一、介绍

　　1、介绍：从文件【big.cpp】读取内容，然后将【读取内容】输出到【屏幕】。

　　2、主程序源文件：iotest.cpp

　　3、被读取的文件：big.cpp

二、源代码

　　1、主程序源代码：iotest.cpp

 1 /*    file_name = iotest.cpp
 2  *
 3  *    date = "2024-01-11"
 4  *
 5  * */
 6 
 7 
 8 #include <iostream>
 9 #include <fstream>
10 #include <string>
11 #include <locale>
12 
13 
14 using namespace std;
15 
16 
17 void read_from_keybord()
18 {
19       string ptin = "[ Input a string ]: ";
20       string ptout = "[ Output ]: ";
21       string s ;
22       cout << ptin << flush ;
23       //cin >> s;
24       getline(cin, s);
25       cout << ptout << s << endl;
26 }
27 
28 
29 void read_from_file()
30 {
31       // set buffer size
32       char s[1020][1020];
33 
34       fstream to_stream;
35       to_stream.open("big.cpp", ios::in);
36 
37       int end_file = 0;
38       for(int i=0; to_stream.getline(s[i], 1000); i++){ end_file = i+1; }
39       // set end of s[]
40       s[end_file][0]='\n';
41 
42       for(int i=0; s[i][0]!='\n'; i++){ cout << i << "\t" << s[i] << endl; }
43 
44       to_stream.close();
45 }
46 
47 
48 int main(int argc, char *argv[], char *envp[])
49 {
50       read_from_file();
51 
52       return 0;
53 }

　　2、被读取的文件：big.cpp

 1 /*    file_name = big.cpp
 2  *
 3  *    date = "2024-01-11"
 4  *
 5  * */
 6 
 7 
 8 #include <iostream>
 9 #include <string>
10 
11 
12 using namespace std;
13 
14 
15 class name{};
16 
17 
18 class big :name
19 {
20 public:
21       big() { cout << "big() "<< endl; }
22 
23       big(string n, string i, string f):name{n},id{i},info{f}
24       { 
25         cout << "    [constructor]: big(string, string, string) "<< endl; 
26       }
27 
28       ~big(){ cout << "    [destructor]: ~big()" << endl;}
29 
30       void msg()
31       { 
32         cout <<"\tid := " << id << endl;  
33         cout <<"\tname := " << name << endl;  
34         cout <<"\tinfo := " << info << endl;  
35       }
36 
37 private:
38       string name;
39       string id;
40       string info; 
41 };
42 
43 
44 int main(int argc, char *argv[], char *envp[])
45 {
46       big b("file", "0xF0B1", "memory");
47       b.msg();
48 
49       return 0;
50 }

三、运行结果

 1 [wit@fedora io]$ alias | grep "gpp"
 2 alias gpp='g++ -g -Wall -std=c++20 -o'
 3 [wit@fedora io]$ 
 4 [wit@fedora io]$ 
 5 [wit@fedora io]$ gpp iotest iotest.cpp && ./iotest
 6 0     /*        file_name = big.cpp
 7 1      *
 8 2      *        date = "2024-01-11"
 9 3      *
10 4      * */
11 5
12 6
13 7     #include <iostream>
14 8     #include <string>
15 9
16 10
17 11    using namespace std;
18 12
19 13
20 14    class name{};
21 15
22 16
23 17    class big :name
24 18    {
25 19    public:
26 20      big() { cout << "big() "<< endl; }
27 21
28 22      big(string n, string i, string f):name{n},id{i},info{f}
29 23      { 
30 24              cout << "    [constructor]: big(string, string, string) "<< endl; 
31 25      }
32 26
33 27      ~big(){ cout << "    [destructor]: ~big()" << endl;}
34 28
35 29      void msg()
36 30      { 
37 31              cout <<"\tid := " << id << endl;  
38 32              cout <<"\tname := " << name << endl;  
39 33              cout <<"\tinfo := " << info << endl;  
40 34      }
41 35
42 36    private:
43 37      string name;
44 38      string id;
45 39      string info; 
46 40    };
47 41
48 42
49 43    int main(int argc, char *argv[], char *envp[])
50 44    {
51 45      big b("file", "0xF0B1", "memory");
52 46      b.msg();
53 47
54 48      return 0;
55 49    }
56 [wit@fedora io]$ 
57 [wit@fedora io]$ 
58 [wit@fedora io]$ gpp big big.cpp && ./big
59     [constructor]: big(string, string, string) 
60       id := 0xF0B1
61       name := file
62       info := memory
63     [destructor]: ~big()
64 [wit@fedora io]$ 
65 [wit@fedora io]$ 
66 [wit@fedora io]$