On Saturday 11 April 2009 22:16:58 Pavel Roskin wrote:
> Quoting "Yoshinori K. Okuji" <ok...@enbug.org>:
> > "test -n" should be avoided. Maybe this is not necessary nowadays, but my
> > old lesson was to use "test x$target_alias != x" instead for portability.
> > Well, "!=" was not very portable, either, maybe.
>
> I believe both "-n" and "!=" are found in Autoconf sources that are
> turned into configure scripts. Anyway, I'll use the syntax you want.
Even if this looks obsolete, I think it is better to follow the
chapter "Limitations of Builtins" in the autoconf manual:
`test' (strings)
Posix says that `test "STRING"' succeeds if STRING is not null,
but this usage is not portable to traditional platforms like
Solaris 10 `/bin/sh', which mishandle strings like `!' and `-n'.
Posix also says that `test ! "STRING"', `test -n "STRING"' and
`test -z "STRING"' work with any string, but many shells (such as
Solaris, AIX 3.2, UNICOS 10.0.0.6, Digital Unix 4, etc.) get
confused if STRING looks like an operator:
$ test -n =
test: argument expected
$ test ! -n
test: argument expected
Similarly, Posix says that both `test "STRING1" = "STRING2"' and
`test "STRING1" != "STRING2"' work for any pairs of strings, but
in practice this is not true for troublesome strings that look
like operators or parentheses, or that begin with `-'.
It is best to protect such strings with a leading `X', e.g., `test
"XSTRING" != X' rather than `test -n "STRING"' or `test !
"STRING"'.
Regards,
Okuji
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