```plaintextlseek(rfd,130,SEEK_SET); read(rfd,buffer,40);What will the read return, and what (if anything) will be placed in buffer?```**Explanation:**In this code snippet, we see two functions used in file handling in C: `lseek` and `read`.1. **lseek(rfd,130,SEEK_SET);** - `lseek` is a system call that repositions the file offset of the open file descriptor `rfd` to the specified location. - The first argument, `rfd`, is the file descriptor of the open file. - The second argument, `130`, is the offset in bytes to which the file pointer will be moved. - `SEEK_SET` is the directive indicating that the offset should be set relative to the beginning of the file.2. **read(rfd,buffer,40);** - `read` attempts to read up to `40` bytes from the file associated with the descriptor `rfd` into `buffer`. - `rfd` is the file descriptor from which to read. - `buffer` is the location where the read data will be stored. - `40` specifies the maximum number of bytes to read.**Discussion Question:**- What will the `read` return, and what (if anything) will be placed in buffer? Students should consider factors such as the file's length, content from the offset position, and any potential errors (e.g., if `rfd` does not refer to a valid file). ```cchar buffer[BUFSIZE];int fd = open("fooey", O_WRONLY|O_CREAT|O_TRUNC, 0777);strcpy(buffer, "First data");write(fd, buffer, strlen(buffer));lseek(fd, 90, SEEK_SET);strcpy(buffer, "Second data");write(fd, buffer, strlen(buffer));lseek(fd, 100, SEEK_END);strcpy(buffer, "Third data");write(fd, buffer, strlen(buffer));close(fd);```a. What is the size of the file at the end of this section of code?b. Describe the contents of the file—say exactly what byte offsets contain actual data, and what offsets constitute "holes".c. Why might holey files be useful?d. Suppose, after the above sequence of writes, the same program opens the file for reading and then does:``````### Explanation- **Code Explanation**: - A buffer is defined to store data. - The file "fooey" is opened with write permissions; it will be created if it does not exist or truncated if it does. - "First data" is written to the file. - The file pointer is moved to byte offset 90, leaving a gap (or hole) between the first and second writes. - "Second data" is written starting at byte 90. - The file pointer is moved 100 bytes beyond the current end of the file. - "Third data" is written starting at the new position.- **Questions and Concepts**: - **Holey Files**: These are files with holes (empty regions) between data blocks, which do not consume disk space. - **File Size Determination**: The file size reflects the position of the farthest byte written in the file. - **Practical Use**: Holey files allow efficient storage of sparse data by not allocating blocks for the empty gaps.

seek(rfd, 130, SEEK_SET);read(rfd, buffer, 40);seek sets the file position to 130 bytes from the…

char buffer [BUFSIZE]; int fd = open("fooey",0_WRONLY|O_CREAT|O_TRUNC,0777); strcpy (buffer, "First data"); write(fd, buffer, strlen(buffer)); 1seek (fd, 90, SEEK_SET); strcpy (buffer, "Second data"); write(fd, buffer, strlen(buffer)); 1seek (fd, 100, SEEK_END); strpcy (buffer, "Third data"); write(fd, buffer, strlen(buffer)); close(fd); a. What is the size of the file at the end of this section of code? b. Describe the contents of the file say exactly what byte offsets contain actual data, and what offsets constitute "holes". c. Why might holey files be useful?

char buffer [BUFSIZE]; int fd = open("fooey",0_WRONLY|O_CREAT|O_TRUNC,0777); strcpy (buffer, "First data"); write(fd, buffer, strlen(buffer)); 1seek (fd, 90, SEEK_SET); strcpy (buffer, "Second data"); write(fd, buffer, strlen(buffer)); 1seek (fd, 100, SEEK_END); strpcy (buffer, "Third data"); write(fd, buffer, strlen(buffer)); close(fd); a. What is the size of the file at the end of this section of code? b. Describe the contents of the file say exactly what byte offsets contain actual data, and what offsets constitute "holes". c. Why might holey files be useful?

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

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