I have a sed replacement command that I would like to be compatible with BSD sed as well as GNU sed.  Extended regular expressions are not an issue as I do not need them in this case.  My primary problem is difference in the way that the two seds interpret character escape sequences in the replacement strings.  My replacement string contains tabs and newlines and I'd like them to be visible in the command strings for ease of maintenance, however, BSD sed doesn't interpret the escape sequences and GNU sed does. What is the appropriate way to instruct sed to interpret these escape sequences on BSD? The following two snippets epitomize my problem:GNU sedecho ABC | sed 's/B/\n\tB\n'yeildsA    BCBSD sedecho ABC | sed 's/B\n\tB\n'yieldsAntBnCClearly, \n and \t aren't interpreted as escape sequences by BSD sedNow, to my question. According the BSD sed manpage:To specify a newline character in the replacement string, precede it  with a backslash.Does this imply that I'd need to precede a literal newline by a backslash? What is the appropriate way to instruct sed to interpret escape sequences like \n in the replacement text? 
How can I instruct BSD sed to interpret escape sequences like \n and \t?
sed;bsd
If you need to write portable scripts, you should stick to features in the POSIX standard (a.k.a. Single Unix a.k.a Open Group Base Specification). Issue 7 a.k.a. POSIX-1.2008 is the latest, but many systems haven't finished adopting it yet. Issue 6 a.k.a POSIX-1.2001 is by and large provided by all modern unices.In sed, the meaning of escape sequences like \t and \n is not portable, except that in a regex, \n stands for a newline. In the replacement text for an s command, \n is not portable, but you can use the sequence backslash-newline to stand for a newline.A portable way to generate a tab character (or any other character expressed in octal) is with tr. Store the character in a shell variable and substitute this variable in the sed snippet.tab=$(echo | tr '\n' '\t')escape=$(echo | tr '\n' '\033')embolden () {  sed -e 's/^/'$escape'[1m/' -e 's/$/'$escape'[0m/'}Note again that newlines need to be expressed differently in regexes and in s replacement texts.You might want to use awk instead. It allows backslash escapes, including octal escapes \ooo, in every string literal.