Strange behaviour in recursive copy

Question

Could someone explain why this happens?

Most specifically: Why is one 1's content copied to f? And why is f copied to g?

$ tree  
.

0 directories, 0 files

$ mkdir 1
$ mkdir 2
$ touch 1/a
$ touch 1/b
$ mkdir 1/c
$ touch 1/c/x
$ tree
.
├── 1
│   ├── a
│   ├── b
│   └── c
│       └── x
└── 2

3 directories, 3 files

$ cp -r 1/* 2/*
zsh: no matches found: 2/*

$ cp -r 1/* 2/*
$ mkdir 2/f
$ mkdir 2/g
$ cp -r 1/* 2/*
$ tree
.
├── 1
│   ├── a
│   ├── b
│   └── c
│       └── x
└── 2
    ├── f
    └── g
        ├── a
        ├── b
        ├── c
        │   └── x
        └── f

7 directories, 6 files

Answer 1

For cp, the destination is the last argument on the command line. You have specified 2/g as the last argument.

Before cp is executed, the command parameters are expanded. 1/* expands to 1/a 1/b 1/c. 2/* expands to 2/f 2/g. The final executed command is cp -r 1/a 1/b 1/c 2/f 2/g, which will copy all the arguments (except the last one) to 2/g.

If you are intending to copy things to 2, the second glob isn't necessary, making the command cp -r 1/* 2/. If you are intending to copy things to multiple destinations, you can't specify that with just cp; you can use a small loop, like the following:

#!/bin/sh
for path in ./2/*/; do
  cp -r 1/* "$path"
done