2.1 File Navigation and Management

Hierarchy

Recall that everything starts at /.

Path concepts (file paths)

• Absolute Path: Starts with /. Always works, no matter where you are. (e.g., /home/user/docs/file.txt).
• Relative Path: Does not start with /. Depends on your current location. (e.g., docs/file.txt or ../file.txt).

Note

Do not confuse file paths with the environment variable $PATH. File paths describe where files are on the system; $PATH is the list of directories the shell searches for executables when you type a command. See it with echo $PATH.

Navigation Commands

Command	Name	Function
pwd	Print Working Directory	Tells you where you are right now.
cd	Change Directory	Moves you to a new folder.
cd ..		Move up one level.
cd ~		Move to your home directory.
cd -		Go back to the previous directory.
ls	List	Shows files in the current directory.

ls Flags

You rarely run just ls. Common flags:

• ls -l: Long listing (permissions, owner, size, date).
• ls -a: All files (shows hidden files starting with .).
• ls -lh: Long listing with human-readable sizes (MB, GB).
• ls -la: Long listing of all files (including hidden).
• ls -ltr: Sort by date (most recent at the end).

Glob patterns (wildcards)

Wildcards help select multiple files:

• *.txt: All .txt files.
• file?.txt: Matches file1.txt, fileA.txt, etc.
• docs/*/index.md: Any index.md inside a subdirectory of docs/.

File Management

Command	Function	Example
mkdir	Make Directory	mkdir projects
touch	Create empty file	touch notes.txt
cp	Copy	cp notes.txt backup.txt
cp -r	Copy Recursive (Folder)	cp -r projects/ projects-backup/
mv	Move (or Rename)	mv notes.txt doc.txt
rm	Remove (Delete)	rm file.txt
rmdir	Remove empty directory	rmdir old-empty-dir
rm -i	Interactive confirmation	rm -i file.txt

Tip

If a path contains spaces, wrap it in quotes: mv "Final Report.txt" reports/.

Finding Files

Common tools to locate files on the system:

find

Searching for files in a directory hierarchy.

• Syntax: find [path] [expression]
• Examples:
  • find /etc -name "*.conf": Find all files in /etc ending with .conf.
  • find . -type f: Find only files in current directory.
  • find . -type d: Find only directories.
  • find /var/log -size +10M: Find files larger than 10MB.
  • find . -perm 777: Find files with 777 permissions.
  • find . -mtime -1: Find files modified in the last 24 hours.
  • find . -user alice: Find files owned by user alice.
  • find . -iname "*.jpg": Case-insensitive match.
  • find . -maxdepth 2 -name "*.md": Limit search depth.
  • find . -not -path "*/node_modules/*": Exclude unwanted directories.
  • find . -type f -name "*.log" -exec ls -l {} \;: Run an action for each result.

locate

Find files by name using a prebuilt database (faster than find but might be outdated).

• Syntax: locate [pattern]
• Update DB: sudo updatedb (updates the database used by locate).

which

Locate a command.

• Example: which python (shows the path to the python executable).

whereis

Locate the binary, source, and manual page files for a command.

• Example: whereis ls

$PATH and command resolution

When you type a command, the shell searches for the executable in each directory in $PATH (separated by :).

• See your PATH: echo $PATH
• Temporarily add a directory: export PATH="$HOME/bin:$PATH"
• Make it persistent:
  • In bash: add the export to ~/.bashrc or ~/.profile
  • In zsh: add it to ~/.zshrc

Tip

If which cannot find a command but the executable exists, ensure its directory is in $PATH, or invoke it with the absolute path (/usr/local/bin/foo) or a relative path (./foo).