How to Read a Struct from a Binary File in C? - GeeksforGeeks (2024)

How to Declare a Struct Inside a Struct in C?

A structure is a composite data type in C programming that enables combining several data types under one name. A structure inside a structure is also called a nested structure. In this article, we will learn how to declare a structure inside a structure in C++. Declare a Struct Inside a Struct in CTo declare a structure inside a structure, we need

How to Write a Struct to a Binary File in C?

C file handling allows users to store the data from a C program to a file in either the text or the binary format. In this article, we will learn how to write a struct to a binary file in C. Writing Structure into a Binary File in CTo write a struct to a binary file, we can use the fwrite() function that writes the given bytes of data in the file i

Is sizeof for a struct equal to the sum of sizeof of each member?

Prerequisite : sizeof operator in C The sizeof for a struct is not always equal to the sum of sizeof of each individual member. This is because of the padding added by the compiler to avoid alignment issues. Padding is only added when a structure member is followed by a member with a larger size or at the end of the structure. Different compilers m

Difference between Struct and Enum in C/C++ with Examples

Structure in C++ A structure is a user-defined data type in C/C++. A structure creates a data type that can be used to group items of possibly different types into a single type. The ‘struct’ keyword is used to create a structure. Syntax: struct structureName{ member1; member2; member3; . . . memberN; }; Below is the implementation: C/C++ Code #inc

Operations on struct variables in C

In C, the only operation that can be applied to struct variables is assignment. Any other operation (e.g. equality check) is not allowed on struct variables. For example, program 1 works without any error and program 2 fails in compilation. Program 1 #include <stdio.h> struct Point { int x; int y; }; int main() { struct Point p1 = {10, 20}; s

Struct Hack

What will be the size of following structure? C/C++ Code struct employee { int emp_id; int name_len; char name[0]; }; 4 + 4 + 0 = 8 bytes.And what about size of "name[0]". In gcc, when we create an array of zero length, it is considered as array of incomplete type that's why gcc reports its size as "0" bytes. This technique is known as "Struct Hack

Conversion of Struct data type to Hex String and vice versa

Most of the log files produced in system are either in binary(0,1) or hex(0x) formats. Sometimes you might need to map this data into readable format. Conversion of this hex information into system defined data types such as 'int/string/float' is comparatively easy. On the other hand when you have some user defined data types such as 'struct' the p

How to Declare a Pointer to a Struct in C?

Structure (or structs) in the C programming language provides a way to combine variables of several data types under one name and pointers provide a means of storing memory addresses. In this article, we will learn how to declare such a pointer to a struct in C. Declaration of Pointer to Struct in CTo declare a pointer to a struct we can use the st

How to Modify Struct Members Using a Pointer in C?

In C++, we use structure to group multiple different types of variables inside a single type. These different variables are called the members of structures. In this article, we will discuss how to modify the struct member using a pointer in C. Example Input: myStruct.mem1 = 10; myStruct.mem2 = 'a'; Output: myStruct.mem1 = 28; myStruct.mem2 = 'z';

How to Initialize Char Array in Struct in C?

In C++, we can also define a character array as a member of a structure for storing strings. In this article, we will discuss how to initialize a char array in a struct in C. Initialization of Char Array in Struct in CWhen we create a structure instance (variable) in C that includes a char array, we can set an initial value for that char array dire

How to Declare a Struct Member Inside a Union in C?

A union contains different types of variables as its members and all these members share a memory location. In this article, we will learn how to declare and access the struct member inside a union in C++. Structure Inside Union in CTo declare a structure inside a union we can use the below syntax: Syntax to Declare Structure Inside Union in Cunion

How to use typedef for a Struct in C?

In C, we use typedef to create aliases for already existing types. For structure, we can define a new name that can be used in place of the original struct name. In this article, we will learn how to create a typedef for a structure in C++. Use the typedef struct in CTo create an alias for a structure in C, we can use the typedef keyword typedef fo

How to Search in Array of Struct in C?

In C, a struct (short for structure) is a user-defined data type that allows us to combine data items of different kinds. An array of structs is an array in which each element is of struct type. In this article, we will learn how to search for a specific element in an array of structs. Example: Input:Person people[3] = { { "Alice", 25 }, { "Bob", 3

How to Pack a Struct in C?

In C, when you declare a structure, the compiler allocates memory for its members, and the way it does this can involve adding padding between members for alignment purposes. struct packing refers to the arrangement of the members of a structure in memory so that there is no extra space left. In this article, we are going to learn how to pack a str

How to Use bsearch with an Array of Struct in C?

The bsearch function in C is a standard library function defined in the stdlib.h header file that is used to perform binary search on array-like structure. In this article, we will learn to use bsearch with an array of struct in C. Input: struct Person people[] = { { 1, "Ram" }, { 2, "Rohan" }, { 4, "Ria" }, { 3, "Mohan" } }; Key: 3 Output: Person

Read/Write Structure From/to a File in C

For writing in the file, it is easy to write string or int to file using fprintf and putc, but you might have faced difficulty when writing contents of the struct. fwrite and fread make tasks easier when you want to write and read blocks of data. Writing Structure to a File using fwrite We can use fwrite() function to easily write a structure in a

C program to read a range of bytes from file and print it to console

Given a file F, the task is to write C program to print any range of bytes from the given file and print it to a console. Functions Used: fopen(): Creation of a new file. The file is opened with attributes as “a” or “a+” or “w” or “w++”.fgetc(): Reading the characters from the file.fclose(): For closing a file. Approach: Initialize a file pointer,

C Program to Read and Print All Files From a Zip File

To understand how to write a C program for reading and printing zip files, it's important to know what exactly a zip file is. At its core, a zip file contains one or more files compressed using specific compression algorithms.Including the compressed data of the files, the zip file contains meta and header information about all files inside the zip

cJSON - JSON File Write/Read/Modify in C

JSON (JavaScript Object Notation) is a lightweight data-interchange format that is easy to read and write for humans and machines alike. JSON is widely used for data exchange between applications and web services. In this article, we will discuss how to read and write JSON data in the C programming language. JSON in C JSON in C can be handled using

Implement your own tail (Read last n lines of a huge file)

Given a huge file having dynamic data, write a program to read last n lines from the file at any point without reading the entire file. The problem is similar to tail command in linux which displays the last few lines of a file. It is mostly used for viewing log file updates as these updates are appended to the log files. Source : Microsoft Intervi

lseek() in C/C++ to read the alternate nth byte and write it in another file

From a given file (e.g. input.txt) read the alternate nth byte and write it on another file with the help of “lseek”. lseek (C System Call): lseek is a system call that is used to change the location of the read/write pointer of a file descriptor. The location can be set either in absolute or relative terms. Function Definition off_t lseek(int fild

How to Read From a File in C?

File handing in C is the process in which we create, open, read, write, and close operations on a file. C language provides different functions such as fopen(), fwrite(), fread(), fseek(), fprintf(), etc. to perform input, output, and many different C file operations in our program. In this article, we will explore how to read from a file in C usin

How to Read a File Line by Line in C?

In C, reading a file line by line is a process that involves opening the file, reading its contents line by line until the end of the file is reached, processing each line as needed, and then closing the file. In this article, we will learn how to read a file line by line in C. Reading a File Line by Line in CIn C, the fgets() function is a standar

C Program to Read Content of a File

In C, reading the contents of a file involves opening the file, reading its data, and then processing or displaying the data. Example Input: File containing "This is a test file.\nIt has multiple lines." Output: This is a test file.It has multiple lines. Explanation: The program reads and displays the multiline text from the file. In this article,

C program to check whether the file is JPEG file or not

Write a C program which inputs a file as a command-line arguments and detects whether the file is JPEG(Joint Photographic Experts Group) or not. Approach: We will give an image as a command line argument while executing the code. Read the first three bytes of the given image(file). After reading the file bytes, compare it with the condition for JPE

C program to copy contents of one file to another file

[GFGTABS] C #include <stdio.h> #include <stdlib.h> // For exit() int main() { FILE *fptr1, *fptr2; char filename[100]; int c; printf("Enter the filename to open for reading: "); scanf("%s", filename); // Open one file for reading fptr1 = fopen(filename, "r"); if (fptr1 == NULL) { printf("Cannot open fi

How to read a PGMB format image in C

PGM or Portable Gray Map file is a grayscale image where each pixel is encoded with 1 or 2 bytes. It contains header information and pixel grayscale values in a matrix form. Approach: The idea is followed to read PGMB format image is as follows: Open a PGMB (binary format PGM image).Extract the pixel information, which can be then used for further

How to input or read a Character, Word and a Sentence from user in C?

C is a procedural programming language. It was initially developed by Dennis Ritchie as a system programming language to write an operating system. The main features of the C language include low-level access to memory, a simple set of keywords, and a clean style, these features make C language suitable for system programmings like operating system

Input-output system calls in C | Create, Open, Close, Read, Write

System calls are the calls that a program makes to the system kernel to provide the services to which the program does not have direct access. For example, providing access to input and output devices such as monitors and keyboards. We can use various functions provided in the C Programming language for input/output system calls such as create, ope

How to Read Data Using sscanf() in C?

In C, sscanf() function stands for "String Scan Formatted". This function is used for parsing the formatted strings, unlike scanf() that reads from the input stream, the sscanf() function extracts data from a string. In this article, we will learn how to read data using sscanf() function in C. Example: Input: char *str = "Ram Manager 30";Output:Nam