`cp` Copy files and directories

Makes a copy of a file, or of several files, in another place. Add -R to copy whole folders. The original stays where it is.

Synopsis

cp [OPTION]... SOURCE TARGET
cp [OPTION]... SOURCE... DIRECTORY

Option or form	What it does
`-R, -r`	Copy a directory and everything inside it. Required for folders
`-i`	Interactive: ask before overwriting an existing file
`-n`	Do not overwrite an existing file
`-f`	Force: replace existing files without asking
`-p`	Preserve the modification time, permissions and, where allowed, owner of each file
`-v`	Verbose: print each file as it is copied
`-a`	Archive mode: copy a tree and keep attributes and symbolic links as they are (same as -RpP on macOS)

Copy a file under a new name

cp notes.txt notes-backup.txt

Copy several files into a folder

cp notes.txt app.log docs

Copy a whole folder

cp -R photos photos-backup

See what is copied and keep file dates

cp -pv data.csv data-copy.csv

Copy without overwriting anything

cp -n notes.txt docs/notes.txt

Ask before replacing a file

cp -i report.pdf /backup/report.pdf

cp overwrites the target without asking when it already exists and you have permission. Use -i to be asked, or -n to never overwrite.
Copying a folder needs -R. Without it cp prints a message that the source is a directory and skips it.
A trailing slash on the source differs between systems. On macOS, cp -R src/ dest copies the contents of src. On GNU/Linux, src and src/ are treated the same, and the folder itself is copied into dest if it exists. Check the result when moving a command between the two.
On macOS -a means -RpP. GNU cp -a is a little different, so state the options you need if exact behaviour matters, for example -Rp.
If the target is an existing folder, the file is copied inside it. If it is not, the target becomes the new file name. Add a trailing slash to the folder name to be sure it is treated as a folder.