I'm not sure whether this is a bug in POSIX or in bash, but I noticed the following with bash-3.2.39.
$ bash -c 'foo=$(cat <<EOF hi EOF) echo $foo' According to http://www.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html#tag_02_0 7_04, heredoc parsing "continues until there is a line containing only the delimiter and a <newline>", and "EOF)" is not a line containing only the delimiter and a <newline>. Therefore, per the rules in http://www.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html#tag_02_0 6_03 that the closing ) is not located until a valid shell script has been seen as the command, this should be interpreted as an unterminated here-doc and an unterminated command-substitution, and cause a syntax error. But bash treats the ) as the conclusion of the command-substitution, the EOF followed by end-of- input as the conclusion of the heredoc, and prints out "hi" without error. On the other hand, I suppose bash is doing something sensible (pdksh and zsh had the same behavior; only ash reported a syntax error), since this next example demonstrates that bash (and ash, zsh, and pdksh) consistently treats end-of-input as a valid heredoc terminator, even though no newline was present. $ printf 'cat <<EOF hi EOF' > foo $ chmod +x foo $ bash ./foo hi A similar case occurs with ``: $ bash -c 'foo=`cat <<EOF hi EOF` echo $foo' Here again, only ash behaves differently (but by printing "hi EOF" rather than complaining of a syntax error); but this time, POSIX is explicit that an unquoted ` in the body of a heredoc causes undefined behavior, and by my earlier arguments, 'EOF`' is still the body of the heredoc. So this is not a valid POSIX test case, and bash neither needs to change behavior, nor needs to keep behavior the same if the $() case is changed. Finally, bash has a definite bug, with no POSIX ambiguities: $ bash -c 'cat <<EOF hi' Here, bash treats end-of-input as the heredoc delimiter, and prints "hi", even though it should be complaining of a syntax error since the heredoc (and thus the script) is unterminated. pdksh behaves correctly and fails with a syntax error. -- Eric Blake
