mkdir / rm / cp / mv

# ===== Create =====
mkdir foo                   # one dir
mkdir -p foo/bar/baz        # parents as needed (the common form)
mkdir -m 700 secret         # set perms at creation

# Multiple at once:
mkdir -p dist/{js,css,images}

# Create a file:
touch hello.txt
touch -t 202404101200 hello.txt   # set mtime

# ===== Remove =====
rm file.txt                 # remove a file (PROMPTS only with -i)
rm -i file.txt              # prompt before each
rm -f file.txt              # force; no prompt, no error if missing
rmdir foo                   # remove EMPTY dir
rm -r foo                   # remove dir + contents (DESTRUCTIVE)
rm -rf foo                  # nuclear; no prompt, no errors

# ===== Copy =====
cp src.txt dst.txt
cp -a srcdir dstdir         # archive: recursive + preserve perms/times/links
cp -v src.txt dst.txt       # verbose
cp -i src.txt dst.txt       # prompt before overwrite
cp -n src.txt dst.txt       # no clobber (do not overwrite)

# Hard / soft links:
ln src.txt link.txt         # hard link
ln -s src.txt symlink.txt   # symlink

# ===== Move / rename =====
mv old.txt new.txt          # rename
mv file.txt dir/            # move into dir
mv -i a b                   # prompt before overwrite
mv -n a b                   # no clobber

# Bulk rename with shell expansion:
for f in *.jpeg; do mv "$f" "${f%.jpeg}.jpg"; done

# ===== Safe defaults =====
# Aliases worth setting in your shell rc:
alias rm='rm -i'
alias cp='cp -i'
alias mv='mv -i'
# Then use \rm if you specifically want non-interactive (or 'command rm').

# ===== Permissions vs ownership =====
chmod 644 file              # rw-r--r--
chmod 755 dir               # rwxr-xr-x (common for dirs)
chmod u+x script.sh         # add execute to user
chmod -R 755 dir            # recursive
chown user:group file
chown -R user:group dir

# Numeric reminders:
# r=4, w=2, x=1
# 7 = rwx, 6 = rw-, 5 = r-x, 4 = r--, 0 = ---

# ===== Find + delete safely =====
find . -type f -name '*.tmp' -print     # preview FIRST
find . -type f -name '*.tmp' -delete    # delete (only after the preview!)

# ===== Where to be careful =====
# - rm -rf /            : destroys everything reachable
# - rm -rf $VAR/*       : if VAR is empty -> rm -rf /*
# - Symlink + rm -r     : may follow into shared content (use rm -r --preserve-root)
# - sudo rm without checking the path

# ===== Patterns to internalise =====
# - mkdir -p for nested dirs
# - rm -ri for interactive recursive
# - Verify with ls + find BEFORE removing
# - Keep a habit: ls, ls, ls, then rm

# ===== Pitfalls =====
# - 'rm $DIR/*' with an empty DIR
# - Glob expansion: rm * .txt (note the space)
# - Quoting filenames with spaces
# - Forgetting that rm does not go to a recycle bin

mkdir -p src/lib
rm -rf build
cp -r src dst
mv old.txt new.txt