The basic uses for file operation in C++
- create a file named test.txt and write some random number in it
- open this file and print all the numbers in this file
- set the read position to get the specific number
The codes for those
#include
#include
using namespace std;
int main()
{
ofstream outfile;
outfile.open("test.txt", ios::out | ios::app | ios::binary);
// write some radom numbers to the file
for (int i = 0; i < 100; i++)
{
int num = rand() % 100;
outfile.write((char*)&num, sizeof(num));
}
outfile.close();
// read all contents of the test.txt file
ifstream infile;
infile.open("test.txt", ios::in | ios::binary);
cout << "Contents of test.txt file: " << endl;
int num;
while (infile.read((char*)&num, sizeof(num)))
{
cout << num << " ";
}
cout << endl;
infile.close();
// read the content from 2nd byte to 5th byte
ifstream infile2;
infile2.open("test.txt", ios::in | ios::binary);
cout << "a number in Contents of test.txt file from 0th: " << endl;
infile2.seekg(0);
infile2.read((char*)&num, sizeof(num));
cout << num << endl;
infile2.seekg(4);
infile2.read((char*)&num, sizeof(num));
cout << "a number in Contents of test.txt file from 1st: " << endl;
cout << num << endl;
infile2.close();
return 0;
}
The corresponding results
Contents of test.txt file:
83 86 77 15 93 35 86 92 49 21 62 27 90 59 63 26 40 26 72 36 11 68 67 29 82 30 62 23 67 35 29 2 22 58 69 67 93 56 11 42 29 73 21 19 84 37 98 24 15 70 13 26 91 80 56 73 62 70 96 81 5 25 84 27 36 5 46 29 13 57 24 95 82 45 14 67 34 64 43 50 87 8 76 78 88 84 3 51 54 99 32 60 76 68 39 12 26 86 94 39 83 86 77 15 93 35 86 92 49 21 62 27 90 59 63 26 40 26 72 36 11 68 67 29 82 30 62 23 67 35 29 2 22 58 69 67 93 56 11 42 29 73 21 19 84 37 98 24 15 70 13 26 91 80 56 73 62 70 96 81 5 25 84 27 36 5 46 29 13 57 24 95 82 45 14 67 34 64 43 50 87 8 76 78 88 84 3 51 54 99 32 60 76 68 39 12 26 86 94 39 83 86 77 15 93 35 86 92 49 21 62 27 90 59 63 26 40 26 72 36 11 68 67 29 82 30 62 23 67 35 29 2 22 58 69 67 93 56 11 42 29 73 21 19 84 37 98 24 15 70 13 26 91 80 56 73 62 70 96 81 5 25 84 27 36 5 46 29 13 57 24 95 82 45 14 67 34 64 43 50 87 8 76 78 88 84 3 51 54 99 32 60 76 68 39 12 26 86 94 39 83 86 77 15 93 35 86 92 49 21 62 27 90 59 63 26 40 26 72 36 11 68 67 29 82 30 62 23 67 35 29 2 22 58 69 67 93 56 11 42 29 73 21 19 84 37 98 24 15 70 13 26 91 80 56 73 62 70 96 81 5 25 84 27 36 5 46 29 13 57 24 95 82 45 14 67 34 64 43 50 87 8 76 78 88 84 3 51 54 99 32 60 76 68 39 12 26 86 94 39 83 86 77 15 93 35 86 92 49 21 62 27 90 59 63 26 40 26 72 36 11 68 67 29 82 30 62 23 67 35 29 2 22 58 69 67 93 56 11 42 29 73 21 19 84 37 98 24 15 70 13 26 91 80 56 73 62 70 96 81 5 25 84 27 36 5 46 29 13 57 24 95 82 45 14 67 34 64 43 50 87 8 76 78 88 84 3 51 54 99 32 60 76 68 39 12 26 86 94 39 83 86 77 15 93 35 86 92 49 21 62 27 90 59 63 26 40 26 72 36 11 68 67 29 82 30 62 23 67 35 29 2 22 58 69 67 93 56 11 42 29 73 21 19 84 37 98 24 15 70 13 26 91 80 56 73 62 70 96 81 5 25 84 27 36 5 46 29 13 57 24 95 82 45 14 67 34 64 43 50 87 8 76 78 88 84 3 51 54 99 32 60 76 68 39 12 26 86 94 39 83 86 77 15 93 35 86 92 49 21 62 27 90 59 63 26 40 26 72 36 11 68 67 29 82 30 62 23 67 35 29 2 22 58 69 67 93 56 11 42 29 73 21 19 84 37 98 24 15 70 13 26 91 80 56 73 62 70 96 81 5 25 84 27 36 5 46 29 13 57 24 95 82 45 14 67 34 64 43 50 87 8 76 78 88 84 3 51 54 99 32 60 76 68 39 12 26 86 94 39
a number in Contents of test.txt file from 0th:
83
a number in Contents of test.txt file from 1st:
86
