Write a file system in c

The only difference is that fprintf and fscanf expects a pointer to the structure FILE. After you compile and run this program, you can see a text file program. When you open the file, you can see the integer you entered.

This program reads the integer present in the program. If you successfully created the file from Example 1 , running this program will get you the integer you entered.

Other functions like fgetchar , fputc etc. Functions fread and fwrite are used for reading from and writing to a file on the disk respectively in case of binary files. To write into a binary file, you need to use the fwrite function. The functions take four arguments:. We declare a structure threeNum with three numbers - n1, n2 and n3 , and define it in the main function as num. The first parameter takes the address of num and the second parameter takes the size of the structure threeNum.

Since we're only inserting one instance of num , the third parameter is 1. Function fread also take 4 arguments similar to the fwrite function as above. In this program, you read the same file program. If you have many records inside a file and need to access a record at a specific position, you need to loop through all the records before it to get the record.

This will waste a lot of memory and operation time. An easier way to get to the required data can be achieved using fseek. The first parameter stream is the pointer to the file. The second parameter is the position of the record to be found, and the third parameter specifies the location where the offset starts.

This program will start reading the records from the file program. Course Index Explore Programiz. Popular Tutorials Data Types in C. C for Loop. Arrays in C Programming. Pointers in C. Find roots of a quadratic equation. Print Pyramids and Patterns. Check prime number. We will provide you with supporting files that include the code structure of solving the assignment.

You will edit the C files we give you. We also provide you with test files to test your code. The test code will call functions inside your C file. You are freeto implement as many helper functions and other C files as you wish. Your file system is implemented over an emulated disk system, which is provided to you. The following is aschematic that illustrates the overall concept of the mountable simple file system.

The gray colored modules in the above schematic are provided by the Linux OS. The blue colored moduleswill be given to you. You are expected to implement the yellow colored module. The disk emulator given to you provides a constant-cost disk CCdisk.

It can be considered as an array of sectors blocks offixed size. You can randomly access any given sector for reading or writing. The CCdisk is implementedas a file on the actual file system.

Therefore, the data you store in the CCdisk is persistent across programinvocations. To mimic the real disk, the CCdisk is divided into sectors of fixed size. For example, we can split thespace into byte sectors. The number of sectors times the size of a sector gives the total size of the disk. In addition to holding the actual file and directory data, we need to store auxiliary data meta data thatdescribes the files and directories in the disk. Thestructure and number of bytes spent on meta data storage depends on the file system design, which is theconcern in this assignment.

As mentioned earlier, the test files we will give you will be calling your C file functions. This means your Cfile will be an API for the test files. We will give you the API function names and you will have to fill them. The following are the API functions you will implement:. A file system is somewhat different from other OS components because it maintains data structures inmemory as well as disk.

The disk data structures are important to manage the space in disk and allocateand de-allocate the disk space. Also, the disk data structures indicate where a file is allocated.

Thisinformation is necessary to access the file. The following is what each function will be doing. On-disk data structures of the file system include a super block, the root directory, free block list, and inodetable. The figure below shows a schematic of the on-disk organization of SFS.

The super block defines the file system geometry. It is also the first block in SFS. So the super block needs tohave some form of identification to inform the program what type of file system format is followed for storingthe data. The figure below shows the proposed structure for the super block. We expect your file system toimplement these features, but some modifications are acceptable provided they are well documented.

Eachfield in the figure is 4 bytes long. For instance, the magic number field is 4 bytes long. With a bytelong block , we can see that there will plenty of unused space in the super block. A file or directory in SFS is defined by an inode.

Remember we simplified the SFS by just having a singleroot directory no subdirectories. This root directory is pointed to by an inode, which is pointed to by thesuper block. The inode structure we use here is slightly simplified too.

To write a C structure to a file, use fwrite. In this C Tutorial , we have learnt how to write variables or char array or stream of data into a file using different function available in C programming with examples. C Programming. C Ternary Operator. C File Operations. C — Write to File When a programs output or some of the variables has to be saved to a storage location on file system, the data has to be written to a file.

The following functions are used to write data into the file.