builtin read -r and backslash-char escape sequences

[John Marshall <john.marshall@sanger.ac.uk>]

Problems with one of my scripts appear to have been caused by dash's read -r translating escape sequences (like \t) whereas several other shells read them literally.  For example:

$ printf '%s' '\a\t\x' > backslashes 
$ dash -c 'read -r foo < backslashes; echo "$foo"' | cat -t
^G^I\x
$ bash -c 'read -r foo < backslashes; echo "$foo"' | cat -t
\a\t\x
$ ksh -c 'read -r foo < backslashes; echo "$foo"' | cat -t
\a\t\x

POSIX says of -r, "Do not treat a <backslash> character in any special way. Consider each <backslash> to be part of the input line" [1].  Translating them as escape sequences doesn't appear to be particularly compatible with this, but conceivably the translation is occurring at some other stage.

Is this the intended behaviour?

Thanks,

    John

[1] http://pubs.opengroup.org/onlinepubs/9699919799/utilities/read.html#tag_20_109_04

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