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

Custom bash script to 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

Useful File Commands

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

xxd <BINARY_NAME.bin>

Terminologies

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Special File

• 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 Linux File System

Block Special Files

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

Character Special Files

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