cp -r creates the destination directory if it doesn't exist (in the two-operand case)

2026-06-12 (3m ago)8 views

#shell#posix#cp

I was reviewing a PR where someone suggested we needed to add mkdir -p dest/app-source before running cp -r . dest/app-source. My instinct said it wasn't necessary, and I confirmed it both by testing locally and by looking up the POSIX spec.

What I tested

$ tree
.
├── dest/
└── foo/
    └── bar/
        ├── file.1
        ├── file.2
        └── file.3
 
$ cp -r foo dest/here   # 'here' doesn't exist yet
 
$ tree
.
├── dest/
│   └── here/           # created automatically!
│       └── bar/
│           ├── file.1
│           ├── file.2
│           └── file.3
└── foo/
    └── bar/
        ├── file.1
        ├── file.2
        └── file.3

here was created automatically. No mkdir -p needed.

Why it works — the POSIX spec

The POSIX spec for cp -R says (https://pubs.opengroup.org/onlinepubs/9699919799/utilities/cp.html):

"If target does not exist and two operands are specified, the name of the corresponding destination path for source_file shall be target"

And separately:

"If the directory dest_file does not exist, it shall be created with file permission bits set to the same value as those of source_file"

The key phrase is "two operands" — meaning exactly one source and one destination (cp src dest). In that case, if dest doesn't exist, cp -r creates it. This is well-defined POSIX behaviour.

The caveat — intermediate directories are NOT created

cp -r only creates the final component of the destination path. If the parent doesn't exist either, you get an error:

$ cp -r foo nonexistent/here
cp: cannot create directory 'nonexistent/here': No such file or directory

In that case you'd need mkdir -p nonexistent/ first. But if the parent already exists, you're fine.

The case where this does NOT apply

If you pass more than two operands (multiple sources), the destination must already exist:

$ cp -r foo bar dest/new   # ERROR — dest/new must already exist when there are 3+ operands

That's the only case where the reviewer's concern would be valid.

GNU vs BSD

On Linux, -r and -R are aliases. On macOS (BSD cp), the man page discourages -r for correctness with symlinks and special files — use -R on macOS. Both create the destination directory in the two-operand case.