The Bourne shell is not a POSIX-compliant shell. The shell specified by the POSIX standard was based on the Bourne shell with some Korn shell changes and extensions.

/bin/sh on most Linux systems is a bash or dash shell with options set so that it is intended to act like a POSIX-compliant shell, but is not tested to conform to POSIX requirements by any POSIX or UNIX conformance test suite.

A here-document has two things that control how it works. In the form:

Code:

command <<word
contents
delimiter

where no part of word is quoted, the input fed into command is the result of performing parameter expansions, command substitutions, and arithmetic expansions on contents. If any part of word is quoted, the input fed into command is contents. The end of contents is identified by a line containing exactly the contents of delimiter immediately followed by a <newline> character where delimiter is word after quote removal has been applied.

In the form:

Code:

command <<-word
contents
delimiter

all leading <tab> characters in each line of contents and in the terminating line containing delimiter are discarded before the actions mentioned above are applied. (Note that it is just leading <tab>s; not leading <tab>s and/or <space>s.)