Kernel.binary_part

You're seeing just the function binary_part, go back to Kernel module for more information.

binary_part(binary, start, length)

binary_part(binary(), non_neg_integer(), integer()) :: binary()

Extracts the part of the binary starting at start with length length. Binaries are zero-indexed.

If start or length reference in any way outside the binary, an ArgumentError exception is raised.

Allowed in guard tests. Inlined by the compiler.

iex> binary_part("foo", 1, 2)
"oo"

A negative length can be used to extract bytes that come before the byte at start:

iex> binary_part("Hello", 5, -3)
"llo"

An ArgumentError is raised when the length is outside of the binary:

binary_part("Hello", 0, 10)
** (ArgumentError) argument error