File

Abstract

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Quote

Linux Kernel is file based but Windows is API based.

This just means that in Linux which follows POSIX, we can use the same file Library Call on Block Special Files, Character Special Files, Socket, Pipe (管道), File System Link & File Directory besides the regular files, where Windows has an separate Windowa API for each of them.

• Hide the nitty gritty of IO Device, so users can focus on manipulating the content inside the IO Device

• Present programmer a clean Abstraction (抽象) of device-independent file

• Examples are Printers & Modems etc

  
  

• 2 parts - Filename & Inode Number, doesn’t have any metadata associated

Create a dummy file with a specified size

This could be useful for testing the Network Throughput.

def generate_dummy_file(file_path, size_gb):
    with open(file_path, 'wb') as f:
        f.write(b'\0' * (1024 * 1024 * 1024 * size_gb))
 
file_path = input("Enter the name for the dummy file: ") + '.bin'
size_gb = int(input("Enter the size in GB: "))
 
generate_dummy_file(file_path, size_gb)
print(f"Dummy file of size {size_gb}GB generated at '{file_path}'")

File Descriptor

• A small Integer (整数) associated with File

File Permission

• In POSIX, file permissions are handled by rwx bits

Special File

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• An Linux Kernel concept - make IO Device look like File, so we can reuse the same set of file System Call (系统调用) on IO Devices
• By convention, kept in the /dev

Block Special Files

• Model IO Device that has a collection of randomly addressable blocks like like Flash Memory

Character Special Files

• Model IO Device that accept or output a character stream like keyboard

Line Break in File

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• POSIX systems uses a single character called Line Feed \n
• While Windows uses carriage return and Line Feed, so 2 characters \r\n. This is because during typewriter times, you needed to mov the carriage to restart typing on the beginning of a line first, then turn the wheel to move the paper to change the line

Hands-On!

You can install dos2unix and unix2dos using Brew to play with line break.

You can view the hidden line break character by downloading and configuring bat.

Useful CLi Tools

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bat

• A cat clone with wings.

brew install bat && echo "alias cat='bat'" >>~/.zshrc

dua

• Manage files fast, powered by rust!

brew install dua-cli
 
dua interactive

xcp

• cp on tren!

cargo install xcp
# Alias to cp
alias cp="xcp"

xxd

• Generate a hexdump from a binary file and display the output

xxd <BINARY_NAME.bin>