Use C language to write file reading and writing tools
In modern software development, file reading and writing is a very common and important operation. By using C language programming, we can easily implement reading and writing of files. This article will introduce how to use C language to write file reading and writing tools, as well as some related precautions.
2 Use C language to write file reading and writing tools
First, we need to include the header file stdio.h. This header file contains some functions for file operations. For example, we can use the fopen function to open a file and return a file pointer to the file. The sample code is as follows:
#include
int main() {
FILE *file;
file = fopen(\example.txt\ \r\ // Other operations
fclose(file);
return 0;
}
In the above example, we used the fopen function to open a file named \example.txt\ and opened it in read-only mode. What needs to be noted here is that if the file is opened successfully, a non-null file pointer is returned; otherwise, NULL is returned.
Next, we can use the fread function to read data from the file. This function takes four parameters: a pointer to the storage location of the data to read, the size of each data item, the number of data items to read, and the file pointer. The sample code is as follows:
#include
int main() {
FILE *file;
int data[100];
file = fopen(\example.txt\ \r\ fread(data, sizeof(int), 100, file);
//Other operations
fclose(file);
return 0;
}
In the above example, we defined an integer array data of size 100 and read 100 integers from the file using the fread function. It should be noted here that if the read is successful, the number of data items actually read is returned; otherwise, less than the expected number of data items is returned.
After reading the file, we can use the fclose function to close the file. This function takes one parameter, which is the pointer to the file to be closed. The sample code is as follows:
#include
int main() {
FILE *file;
file = fopen(\example.txt\ \r\ // Other operations
fclose(file);
return 0;
}
In the above example, we closed the file using the fclose function. It should be noted here that if the shutdown is successful, 0 is returned; otherwise, a non-0 value is returned.
In addition to reading files, we can also write data to files using the fwrite function. This function takes four parameters: a pointer to the storage location of the data to be written, the size of each data item, the number of data items to be written, and the file pointer. The sample code is as follows:
#include
int main() {
FILE *file;
int data[100];
file = fopen(\example.txt\ \w\ fwrite(data, sizeof(int), 100, file);
//Other operations
fclose(file);
return 0;
}
In the above example, we defined an integer array data of size 100 and used the fwrite function to write 100 integers to the file.
It should be noted that when using the fwrite function to write to a file, if the file already exists, the original content will be overwritten; if the file does not exist, a new file will be created. In addition, in order to ensure that the data is successfully written to the file, we need to use the fflush function to refresh the file buffer after writing the file, and use the fclose function to close the file.
To sum up, by using C language programming, we can easily implement reading and writing of files. Use the fopen function to open the file, use the fread function to read the file, use the fwrite function to write to the file, and finally use the fclose function to close the file. At the same time, we need to pay attention to how the file is opened (read-only, write-only, append, etc.), and to close the file promptly after operating the file.
I hope this article will help you learn to use C language to write file reading and writing tools. If you have any questions or suggestions, please feel free to contact us.
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