Navigating and finding files

Command What it does
pwd Shows the current directory
cd <path> Moves into a directory (cd .. goes up one level, cd ~ goes home)
ls Lists files in the current directory (ls -la shows hidden files and details)
find <path> -name "<pattern>" Searches for files by name
which <command> Shows where a command is installed

Working with files

Command What it does
touch <file> Creates an empty file
mkdir <dir> Creates a directory (mkdir -p makes parent directories too)
cp <src> <dest> Copies a file or directory (cp -r for directories)
mv <src> <dest> Moves or renames a file
rm <file> Deletes a file (rm -r for a directory, use carefully)
cat <file> Prints a file's contents to the screen
less <file> Opens a file for scrollable reading (q to quit)
head -n 10 <file> Shows the first 10 lines of a file
tail -n 10 <file> Shows the last 10 lines (tail -f follows a file as it grows, useful for logs)

Searching and text processing

Command What it does
grep "<pattern>" <file> Searches a file for lines matching a pattern (grep -r searches a whole directory)
wc -l <file> Counts lines in a file
sort <file> Sorts lines alphabetically or numerically (sort -n for numbers)
uniq Removes adjacent duplicate lines (usually paired with sort first)
awk '{print $1}' <file> Prints a specific column from structured text
sed 's/old/new/g' <file> Replaces text in a file

Permissions and processes

Command What it does
chmod +x <file> Makes a file executable
ps aux Lists running processes
kill <pid> Stops a process by its process ID
top Shows live resource usage by process (q to quit)

Networking and remote work

Command What it does
curl <url> Fetches a URL, useful for testing an API
ssh user@host Connects to a remote machine
scp <file> user@host:<path> Copies a file to or from a remote machine

Piping and combining commands

Symbol What it does
` `
> Writes output to a file, overwriting it
>> Appends output to a file
&& Runs the next command only if the first one succeeds