Two precautions for using fstream

Two precautions for using fstream-general Linux technology-Linux programming and kernel information. The following is a detailed description. 1. open the file in append Mode

Ofstream oFile;
OFile. open (strFileName. c_str (), ios_base: binary | ios_base: out | ios_base: app );

In this case, where do you think is the write pointer of the oFile? File Header? File tail? In fact, in linux, it is the end of the file, and in windows, it is the file header. Because, if you are programming in windows, remember to do the following after opening the file:

OFile. seekp (0, ios: end );

2. Cross-read/write of fstream

If you need to use fstream to read and write a file for a while, and then read and write "Cross" reads and writes similar to this, pay special attention to it, otherwise, you do not know where the error is. Some strange and difficult-to-locate problems may occur. Because fstream has a read pointer and a write pointer. Getg seekg is used to obtain and set the read pointer, getp seekp is used to obtain and set the write pointer. If you change from a read operation to a write operation, you must use seekp to set the write pointer. Similarly, if you change from a write operation to a read operation, you must use seekp to set the read pointer. Otherwise, you will see the ghost. What you read is not what you want.