Random access to files in C involves positioning the file pointer at a specific location within a file and performing read or write operations from that point. The fseek and ftell functions are commonly used for random access.

Examples :

Program.c

#include <stdio.h> // Function to write data to a file at a specific position void writeToPosition(const char filename[], long position, const char *data) { FILE *file = fopen(filename, "r+"); if (file == NULL) { perror("Error opening file"); return; } // Move the file pointer to the specified position if (fseek(file, position, SEEK_SET) != 0) { perror("Error seeking to position"); fclose(file); return; } // Write data to the file if (fprintf(file, "%s", data) < 0) { perror("Error writing to file"); } else { printf("Write to position successful.\n"); } fclose(file); } // Function to read data from a file at a specific position void readFromPosition(const char *filename, long position, int size) { FILE *file = fopen(filename, "r"); if (file == NULL) { perror("Error opening file"); return; } // Move the file pointer to the specified position if (fseek(file, position, SEEK_SET) != 0) { perror("Error seeking to position"); fclose(file); return; } // Read data from the file char buffer[size]; if (fread(buffer, 1, size, file) != size) { perror("Error reading from file"); } else { printf("Read from position: %.*s\n", size, buffer); } fclose(file); } int main() { const char *filename = "random_access.txt"; // Writing data at a specific position writeToPosition(filename, 10L, "World!"); // Reading data from a specific position readFromPosition(filename, 5L, 6); return 0; }

In this example:

- The writeToPosition function writes data to a file at a specific position, given by the position parameter.
- The readFromPosition function reads data from a file at a specific position, given by the position parameter and reads size bytes.
Note: The SEEK_SET constant is used with fseek to set the file position relative to the beginning of the file. Other constants like SEEK_CUR and SEEK_END can be used for different positioning methods.