System Navigation

These commands help you navigate the Linux file system and find information about files and directories.

cd

Changes the current working directory.

cd [directory]

Special directories:

cd ~: Change to your home directory
cd -: Change to the previous directory
cd ..: Change to the parent directory
cd /: Change to the root directory

Examples:

# Change to home directory
cd ~

# Change to /etc directory
cd /etc

# Go up one directory level
cd ..

# Go to the previous directory
cd -

ls

Lists files and directories in the current directory.

ls [options] [directory]

Options:

-l: List in long format (permissions, owner, size, date)
-a: List all files (including hidden files)
-h: Human-readable file sizes
-S: Sort by file size
-t: Sort by modification time
-r: Reverse order while sorting
--color=auto: Colorize the output

Examples:

# List all files with details
ls -la

# List files sorted by size
ls -lS

# List files with human-readable sizes
ls -lh

pwd

Prints the current working directory (full path).

pwd [options]

Options:

-L: Use PWD from environment (logical path)
-P: Show the physical path without symbolic links

find

Searches for files and directories in a directory hierarchy.

find [path] [expression]

Common expressions:

-name pattern: Search by name
-type f|d: Search for files (f) or directories (d)
-size n: Search by size
-mtime n: Search by modification time
-exec command {} \;: Execute a command on found items

Examples:

# Find all .txt files in the current directory and subdirectories
find . -name "*.txt"

# Find all directories named "log"
find / -type d -name log

# Find files larger than 100MB
find /home -type f -size +100M

# Find files modified in the last day
find /var/log -type f -mtime -1

whereis

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

whereis [options] command

Options:

-b: Search only for binaries
-m: Search only for manual pages
-s: Search only for source files

Examples:

# Find all locations related to the ls command
whereis ls

# Find only the binary for grep
whereis -b grep

which

Shows the full path of shell commands.

which [options] command

Options:

-a: Print all matching paths, not just the first

Examples:

# Find the path to the python command
which python

# Find all python executables in PATH
which -a python

tree

Displays directory structure in a tree-like format.

tree [options] [directory]

Options:

-L level: Limit the depth of recursion
-d: List directories only
-f: Print the full path prefix for each file
-a: Show all files (including hidden files)

Examples:

# Display directory tree with 2 levels
tree -L 2

# Display only directories
tree -d

locate

Finds files by name using a previously built database.

locate [options] pattern

Options:

-i: Ignore case distinctions
-c: Output the number of matching entries
-l number: Limit the output to a specified number of files

Examples:

# Find all files with "config" in the name
locate config

# Find files ignoring case
locate -i README

updatedb

Updates the file name database used by locate.

sudo updatedb [options]

Options:

-U directory: Only update the database for the specified directory