2009-07-19 21:07:20 -0400, Chet Ramey: [...] > > Note that it's a known non POSIX-conformance of bash. > > > > POSIX is explicit that > > > > echo -e > > > > Should output "-e\n". > > That's why bash has the `xpg_echo' option. You can build bash in such > a way that it's always enabled. [...]
Well, that doesn't help when you intend to write a portable script. If you write a script that has "echo -e", POSIX guarantees that it outputs "-e\n" as long as you're on a POSIX system in a POSIX environment. It's hardly documented anywhere that for instance, on Linux (where sh is generally bash based), to get into a POSIX environment, you would need to have "SHELLOPTS=xpg_echo" in your environment. Anyway, note that xpg_echo doesn't turn on POSIX conformance: $ ./bash --norc bash-4.0$ shopt -s xpg_echo bash-4.0$ echo -e bash-4.0$ echo $BASH_VERSION 4.0.0(1)-release bash-4.0$ (same with 3.2). "xpg_echo" turns on Unix conformance only for arguments to echo that contain "\"s (and the behavior for those is unspecified by POSIX, that's part of the XSI extension). What POSIX says is that: echo -n xxxx And echo 'xxx\yyy' are unspecified. The rest is clearly specified. Unix specifies echo fully. echo -n should output "-n<LF>" echo '\t\c' should output "<Tab>" Note that bash conforms to the LSB on this which allows any option to "echo". I wouldn't be surprised if future versions of POSIX did the same as in effect, many shell implementations beside bash do support other options beside "-n". regards, Stephane
