Files I/O
Why files are required?
- To store or retrieve large volume of data as limited data can be displayed on console.
- Usually data gets lost when program is terminated, You can access the data present in a file even when the program is terminated.
- Handling and transferring data from one system to another is quite easier using files
File handling in C?
File operations like create, update, read, and deleting files which are stored on the local file system can be performed in C.
You need to declare a pointer of type File as below:
FILE *fptr;
1. Create or Update a file
First, you need to open file in order to create or update.
Syntax for opening a file
fptr = fopen("filename","mode");
Modes of opening files
| Mode | Description |
|---|---|
| r | Opens for reading. |
| rb | Opens for reading in binary mode. |
| r+ | Opens for both reading and writing. |
| w | Opens for writing. |
| wb | Opens for writing in binary mode. |
| a | Opens for append. |
| ab | Opens for append in binary mode. |
| w+ | Opens for both reading and writing. |
| wb+ | Opens for both reading and writing in binary mode. |
| rb+ | Opens for both reading and writing in binary mode. |
| a+ | Opens for both reading and appending. |
| ab+ | Opens for both reading and appending in binary mode. |
Example
fptr = fopen("C:\\samples\\sample.txt","w");
Consider sample.txt is not present in the above path then it creates a file named sample.txt and opens it for writing.
2. Read and write to a file
fprintf() and fscanf() are used to read and write to a file. They are similar to printf() and scanf() but they are file versions and expects a pointer to the structure file.
Syntax to read a file
FILE * fptr;
fptr = fopen(“fileName.txt”, “r”);
fscanf(fptr, "format specifier", data);
Syntax to write a file
FILE * fptr;
fptr = fopen(“fileName.txt”, “w”);
fprintf(fptr, "format specifier", data);
Any file which is opened for read or write should be closed
Syntax to close a file
fclose(fptr);