File

Abstract

---

• 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

File Descriptor

• A small Integer (整数) associated with File

File Permission

• In POSIX, file permissions are handled by rwx bits

File Compression

• Process of reducing the size of one or more files to save storage space

Compress files in different folders without including the parent directories of the path

#!/bin/bash
set -eu
set -o pipefail
 
# Check if a filename argument is provided
if [ "$#" -eq 0 ]; then
 echo "Usage: xyz <filename> <path1> [<path2> ...]"
 exit 1
fi
 
filename=$1
 
# Create a temporary directory
mkdir myTempZip
 
# Copy required files to the temporary directory
for arg in "${@:2}"; do
 cp -R "$arg" ./myTempZip
 echo "$arg"
done
 
# Navigate to the temporary directory
cd myTempZip
 
# Zip the contents of the directory
zip -r "$filename" *
 
# Move the zip file to the parent directory
mv "$filename" ../
 
# Navigate back to the original directory
cd ..
 
# Remove the temporary directory
rm -rf myTempZip

Special File

---

• 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

---

• 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

---

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>