第十七章记录完成

source/chapter17/append.cpp

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+// append.cpp -- appending information to a file
+#include <iostream>
+#include <fstream>
+#include <string>
+#include <cstdlib>      // (or stdlib.h) for exit()
+
+const char * file = "guests.txt";
+int main()
+{
+    using namespace std;
+    char ch;
+
+// show initial contents
+    ifstream fin;
+    fin.open(file);
+
+    if (fin.is_open())
+    {
+        cout << "Here are the current contents of the "
+             << file << " file:\n";
+        while (fin.get(ch))
+            cout << ch;
+        fin.close();
+    }
+
+// add new names
+    ofstream fout(file, ios::out | ios::app);
+    if (!fout.is_open())
+    {
+        cerr << "Can't open " << file << " file for output.\n";
+        exit(EXIT_FAILURE);
+    }
+
+    cout << "Enter guest names (enter a blank line to quit):\n";
+    string name;
+    while (getline(cin,name) && name.size() > 0)
+    {
+          fout << name << endl;
+    }
+    fout.close();
+
+// show revised file
+    fin.clear();    // not necessary for some compilers
+    fin.open(file);
+    if (fin.is_open())
+    {
+        cout << "Here are the new contents of the "
+             << file << " file:\n";
+        while (fin.get(ch))
+            cout << ch;
+        fin.close();
+   }
+    cout << "Done.\n";
+    // cin.get();
+    return 0; 
+}

source/chapter17/binary.cpp

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+// binary.cpp -- binary file I/O
+#include <iostream> // not required by most systems
+#include <fstream>
+#include <iomanip>
+#include <cstdlib>  // (or stdlib.h) for exit()
+
+inline void eatline() { while (std::cin.get() != '\n') continue; }
+struct planet
+{
+    char name[20];      // name of planet
+    double population;  // its population
+    double g;           // its acceleration of gravity
+};
+
+const char * file = "planets.dat";
+
+int main()
+{
+    using namespace std;
+    planet pl;
+    cout << fixed << right;
+
+// show initial contents
+    ifstream fin;
+    fin.open(file, ios_base::in |ios_base::binary);  // binary file
+    //NOTE: some systems don't accept the ios_base::binary mode
+    if (fin.is_open())
+    {
+    cout << "Here are the current contents of the "
+        << file << " file:\n";
+    while (fin.read((char *) &pl, sizeof pl))
+    {
+        cout << setw(20) << pl.name << ": "
+              << setprecision(0) << setw(12) << pl.population
+              << setprecision(2) << setw(6) << pl.g << endl;
+    }    
+    fin.close();
+    }
+
+// add new data
+    ofstream fout(file, 
+             ios_base::out | ios_base::app | ios_base::binary);
+    //NOTE: some systems don't accept the ios::binary mode
+    if (!fout.is_open())
+    {
+        cerr << "Can't open " << file << " file for output:\n";
+        exit(EXIT_FAILURE);
+    }
+
+    cout << "Enter planet name (enter a blank line to quit):\n";
+    cin.get(pl.name, 20);
+    while (pl.name[0] != '\0')
+    {
+        eatline();
+        cout << "Enter planetary population: ";
+        cin >> pl.population;
+        cout << "Enter planet's acceleration of gravity: ";
+        cin >> pl.g;
+        eatline();
+        fout.write((char *) &pl, sizeof pl);
+        cout << "Enter planet name (enter a blank line "
+                "to quit):\n";
+        cin.get(pl.name, 20);
+    }
+    fout.close();
+
+// show revised file
+    fin.clear();    // not required for some implementations, but won't hurt
+    fin.open(file, ios_base::in | ios_base::binary);
+    if (fin.is_open())
+    {
+        cout << "Here are the new contents of the "
+             << file << " file:\n";
+        while (fin.read((char *) &pl, sizeof pl))
+        {
+            cout << setw(20) << pl.name << ": "
+                 << setprecision(0) << setw(12) << pl.population
+                 << setprecision(2) << setw(6) << pl.g << endl;
+        }
+        fin.close();
+    }
+    cout << "Done.\n";
+// keeping output window open
+    // cin.clear();
+    // eatline();
+    // cin.get();
+    return 0; 
+}

source/chapter17/check_it.cpp

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+// check_it.cpp -- checking for valid input
+#include <iostream>
+
+int main()
+{
+    using namespace std;
+    cout << "Enter numbers: ";
+
+    int sum = 0;
+    int input;
+    while (cin >> input)
+    {
+        sum += input;
+    }
+
+    cout << "Last value entered = " << input << endl;
+    cout << "Sum = " << sum << endl;
+/* keeping output window open */
+/*
+    cin.clear();
+    while (cin.get() != '\n')
+        continue;
+    cin.get();
+*/
+    return 0;
+}

source/chapter17/cinexcp.cpp

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+// cinexcp.cpp -- having cin throw an exception
+#include <iostream>
+#include <exception>
+
+int main()
+{
+    using namespace std;
+    // have failbit cause an exception to be thrown
+    cin.exceptions(ios_base::failbit);
+    cout << "Enter numbers: ";
+    int sum = 0;
+    int input;
+    try {
+        while (cin >> input)
+        {
+            sum += input;
+        }
+    } catch(ios_base::failure & bf)
+    {
+        cout << bf.what() << endl;
+        cout << "O! the horror!\n";
+    }
+
+    cout << "Last value entered = " << input << endl;
+    cout << "Sum = " << sum << endl;
+/* keeping output window open */
+/*
+    cin.clear();
+    while (cin.get() != '\n')
+        continue;
+    cin.get();
+*/
+
+    return 0;
+}

source/chapter17/count.cpp

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+// count.cpp -- counting characters in a list of files
+#include <iostream>
+#include <fstream>
+#include <cstdlib>          // or stdlib.h
+int main(int argc, char * argv[])
+{
+    using namespace std;
+    if (argc == 1)          // quit if no arguments
+    {
+        cerr << "Usage: " << argv[0] << " filename[s]\n";
+        exit(EXIT_FAILURE);
+    }
+
+    ifstream fin;              // open stream
+    long count;
+    long total = 0;
+    char ch;
+
+    for (int file = 1; file < argc; file++)
+    {
+        fin.open(argv[file]);  // connect stream to argv[file]
+        if (!fin.is_open())
+        {
+            cerr << "Could not open " << argv[file] << endl;
+            fin.clear();
+            continue;
+        }
+        count = 0;
+        while (fin.get(ch))
+            count++;
+        cout << count << " characters in " << argv[file] << endl;
+        total += count;
+        fin.clear();           // needed for some implementations
+        fin.close();           // disconnect file
+    }
+    cout << total << " characters in all files\n";
+
+    return 0; 
+}

source/chapter17/defaults.cpp

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+// defaults.cpp -- cout default formats
+#include <iostream>
+
+int main()
+{
+    using std::cout;
+    cout << "12345678901234567890\n";
+    char ch = 'K';
+    int t = 273;
+    cout << ch << ":\n";
+    cout << t << ":\n";
+    cout << -t <<":\n";
+
+    double f1 = 1.200;
+    cout << f1 << ":\n";
+    cout << (f1 + 1.0 / 9.0) << ":\n";
+
+    double f2 = 1.67E2;
+    cout << f2 << ":\n";
+    f2 += 1.0 / 9.0;
+    cout << f2 << ":\n";
+    cout << (f2 * 1.0e4) << ":\n";
+
+
+    double f3 = 2.3e-4;
+    cout << f3 << ":\n";
+    cout << f3 / 10 << ":\n";
+    // std::cin.get();
+    return 0; 
+}

source/chapter17/fileio.cpp

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+// fileio.cpp -- saving to a file
+#include <iostream> // not needed for many systems
+#include <fstream>
+#include <string>
+
+int main()
+{
+    using namespace std;
+    string filename;
+
+    cout << "Enter name for new file: ";
+    cin >> filename;
+
+// create output stream object for new file and call it fout
+    ofstream fout(filename.c_str());
+
+    fout << "For your eyes only!\n";        // write to file
+    cout << "Enter your secret number: ";   // write to screen
+    float secret;
+    cin >> secret;
+    fout << "Your secret number is " << secret << endl;
+    fout.close();           // close file
+
+// create input stream object for new file and call it fin
+    ifstream fin(filename.c_str());
+    cout << "Here are the contents of " << filename << ":\n";
+    char ch;
+    while (fin.get(ch))     // read character from file and
+        cout << ch;         // write it to screen
+    cout << "Done\n";
+    fin.close();
+    // std::cin.get();
+    // std::cin.get();
+    return 0; 
+}

source/chapter17/files.cpp

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+// files.cpp -- saving to a file
+#include <iostream> // not needed for many systems
+#include <fstream>
+#include <string>
+#include <sstream>
+
+int main()
+{
+    using namespace std;
+    string filename = "file";
+
+
+
+// create output stream object for new file and call it fout
+	int i;
+	for (i = 0; i < 140; i++)
+	{
+		   ostringstream outstr;   // manages a string stream
+		   outstr << filename << i;
+		string fname = outstr.str();
+        ofstream fout(fname.c_str());
+		if (!fout.is_open())
+			break;
+		fout << "For your eyes only!\n";        // write to file
+        fout.close();           // close file
+		fout.clear();
+	}
+	cout << "i: " << i << endl;
+    // std::cin.get();
+    // std::cin.get();
+    return 0; 
+}

source/chapter17/fill.cpp

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+// fill.cpp -- changing fill character for fields
+#include <iostream>
+
+int main()
+{
+    using std::cout;
+    cout.fill('*');
+    const char * staff[2] = { "Waldo Whipsnade", "Wilmarie Wooper"};
+    long bonus[2] = {900, 1350};
+
+    for (int i = 0; i < 2; i++)
+    {
+        cout << staff[i] << ": $";
+        cout.width(7);
+        cout << bonus[i] << "\n";
+    }
+    // std::cin.get();
+    return 0; 
+}