File Handling in C The process of file handling refers to how we store the available data or info in a file with the help of a program. The C language stores all the data available in a program into a file with the help of file handling in C. This data can be fetched/extracted from these files to work again in any program.What is File Handling in C? File handling refers to the method of storing data in the C program in the form of an output or input that might have been generated while running a C program ina data file, i.e. a binary file or a text file for future analysis and reference in that very program. What is a File in C? A file refers to a source in which a program stores the information/data in the form of bytes of sequence on a disk (permanently). The content available on a file isn’t volatile like the compiler memory in C. But the program can perform various operations, such as creating, opening, reading a file, or even manipulating the data present inside the file. This process is known as file handling in C. ’Types of Files in a C Program When referring to file handling, we refer to files in the form of data files. Now, these data files are available in 2 distinct forms in the C language, namely: * Text Files * Binary Files Text Files The text files are the most basic/simplest types of files that a user can create in aC program. We create the text files using an extension .txt with the help of a simple text editor. In general, we can use notepads for the creation of .txt files. These files store info internally in ASCII character format, but when we open these files, the content/text opens in a human-readable form. Text files are, thus, very easy to access as well as use. But there’s one major disadvantage; it lacks security. Since a .txt file can be accessed easily, information isn’t very secure in it. ’Types of Files ina C Program When referring to file handling, we refer to files in the form of data files. Now, these data files are available in 2 distinct forms in the C language, namely: ¢ Text Files Binary Files Text Files The text files are the most basic/simplest types of files that a user can create in aC program. We create the text files using an extension .txt with the help of a simple text editor. In general, we can use notepads for the creation of .txt files. These files store info internally in ASCII character format, but when we open these files, the content/text opens in a human-readable form. Text files are, thus, very easy to access as well as use. But there’s one major disadvantage; it lacks security. Since a .txt file can be accessed easily, information isn’t very secure init (ii [2 [7 _ _ ,Binary Files The binary files store info and data in the binary format of 0’s and 1's (the binary number system). Thus, the files occupy comparatively lesser space in the storage. In simpler words, the binary files store data and info the same way a computer holds the info in its memory. Thus, it can be accessed very easily as compared toatext — x file. _The binary files are created with the extension .bin in a program, and it overcomes the drawback of the text files in a program since humans can’t read it; only machines can. Thus, the information becomes much more secure. Thus, binary files are safest in terms of storing data files in aC program.Operators/Functions that We Use for File Handling in C We can use a variety of functions in order to open a file, read it, write more data, create a new file, close or delete a file, search for a file, etc. These are known as file handling operators in C. Here’s a list of functions that allow you to do so: Description of Function Function in Use used to open an existing file or | fopen() a new file writing data into an available | fprintf() file reading the data available in | fscanf() a file ’Description of Function Function in Use used to open an existing file or | fopen() anew file writing data into an available | fprintf() file reading the data available in | fscanf() a file writing any character into the | fputc() program file reading the character from fgetc() an available file used to close the program file | fclose() used to set the file pointer to | fseek() the intended file position writing an integer into an fputw() available file .@s—_—_—_—eee ’used to set the file pointer to | fseek() the intended file position writing an integer into an fputw() available file used to read aninteger from | fgetw() the given file used for reading the current ftell() position of a file sets an intended file pointer to | rewind() the file’s beginning itself KD Note: It is important to know that we must declare a file-type pointer when we are working with various files in a program. This helps establish direct communication between a program and the files. =Operations Done in File Handling The process of file handling enables a user to update, create, open, read, write, and ultimately delete the file/content in the file that exists on the C program’s local file system. Here are the primary operations that you can perform on a file ina C program: ¢ Opening a file that already exists ¢ Creating a new file * Reading content/ data from the existing file ¢ Writing more data into the file ¢ Deleting the data in the file or the file altogetherOpening a File in the Program — to create and edit data We open a file with the help of the fopen() function that is defined in the header file- stdio.h. Here is the syntax that we follow when opening a file: ptr = fopen (“openfile” , “openingmode’); Let us take a look at an example for the same, fopen (“E:\\myprogram \ \recentprogram.txt” , ny"): fopen (“E:\\myprogram \ \previousprogram.bin” , “rb") l¢ Here, if we suppose that the file - recentprogram.txt doesn't really exist in the E:\\myprogram location. Here, we have used the mode “w”. Thus, the first function will create a new file with the name recentprogram.txt and then open it for writing (since we have used the “w" mode). ¢ The “w" here refers to writing mode. It allows a programmer to overwrite/edit and create the contents in a program file. ¢ Now, let us take a look at the second binary previousprogram.bin file that is present in the E:\\myprogram location. Thus, the second function here will open the file (that already exists) for reading in the “rb” binary mode. ¢ The “rb” refers to the reading mode. It only allows you to read a file, but not overwrite it. Thus, it will only read this available file in the program. ZzLl Program Mod | Meaning of Mode ein Prog ram r Open a file for reading the content. rb Open a file for reading the content in binary mode. Opening Modes of C in Standard I/O of a When the file doesn’t exist In case the file doesn't exist in the location, then fopen() will return NULL. In case the file doesn't exist in the location, then fopen() will return NULL. /wb Open a file for writing the content. Open a file for writing the content in binary mode. In case the file exists, its contents are overwritten. In case the file doesn't exist in the location, then it will create a new file. In case the file exists, then its contents will get overwritten. In case the file doesn't exist in the location, then it will create a new file. s| oo ab Open a file for appending the content. Meaning, the data of the program is added to the file's endina program. Open a file for appending the content in binary mode. Meaning, the data of the program is added to the file's end ina program ina binary mode. In case the file doesn't exist in the location, then it will create a new file. In case the file doesn't exist in the location, then it will create a new file. tfa r+ Open a file for In case the file both writing and | doesn't exist reading the in the content. location, then fopen() will return NULL. rb+ | Open a file for In case the file both writing and | doesn't exist reading the in the content in binary | location, then mode. fopen() will return NULL.wb+ ab+ Open a file for both writing and reading the content in binary mode. Open a file for both appending and reading the content. Open a file for both appending and reading the content in binary mode. In case the file exists, its contents are overwritten. In case the file doesn't exist in the location, then it will create a new file. In case the file doesn't exist in the location, then it will create a new file. In case the file doesn't exist in the location, then it will create a ,How do we close a file? Once we write/read a file in a program, we need to close it (for both binary and text files). To close a file, we utilise the fclose() function in a program. Here is how the program would look like: fclose(fptr); In this case, the fptr refers to the file pointer that is associated with that file that needs to be closed in a program.ef How do we close a file? Once we write/read a file in a program, we need to close it (for both binary and text files). To close a file, we utilise the fclose() function in a program. Here is how the program would look like: fclose(fptr); In this case, the fptr refers to the file pointer that is associated with that file that needs to be closed in a program.How do we read and write the data to the text file? We utilise the fscanf() and fprintf() to write and read the data to the text file. These are basically the file versions of the scanf() and printf(). But there is a major difference, ie., both fscanf() and fprintf() expect a pointer pointing towards the structure FILE in the program. Example #1: Writing Data to the Text File in a Program #include #include int main() { int val; FILE *fptr; sExample #1: Writing Data to the Text File ina Program #include #include int main() { int val; FILE *fptr; // if you are using Linux or MacOS, then you must use appropriate locations fptr = fopen (“c:\ \currentprogram.txt’,"w"); if(fptr == NULL) { printf(“File type invalid!”); exit(1); } ’printf(“Please enter the val: "); scanf(“%d’,&val); fprintf(fptr,"%d",val); fclose(fptr); return 0; } The program mentioned here would take the number given by then store it in the currentprogram.txt file. Once we compile this program and run it on the system, we will be able to witness a currentprogram.txt text file created in the C drive of our computer! Also, when we open this file, then we will be able to see what integer we entered as an input while coding. ‘Example #2: Reading Information from the Text File in a Program #include #include int main() { int val; FILE *fptr; // The program will exit in case the file pointer fptr returns NULL. if ((fptr = fopen(“c:\ \currentprogram.txt”,"r”)) == NULL) { printf(“Visible error detected. Cannot open the file!”); exit(1); } ther it any question:fscanf(fptr,"%d", &val); printf(’The value of the integer n is=%d", val); fclose(fptr); return 0; } The program given here would read the integer that we have input in the currentprogram.txt file and then print the integer as an output on the computer screen.How do we Read and Write the Data to the Binary File ina Program? We have to use the functions fwrite() and fread() for writing to and reading from a file present on a disk respectively, for the binary files. When Writing to the Binary File We utilise the function fwrite() for writing the data into a binary file in the program. This function would primarily take four arguments: ¢ the address of the data that would be written on the disk the size of this data ¢ total number of such types of data on the disk ¢ the pointers to those files where we would be writing /When Reading from the Binary File Just like the above-used function fwrite(), the function fread() also takes 4 arguments (lik above). It would go something like this: fread (address_of_Data, size_of_Data, numbers _of_Data, pointerToFile);