POSIX defines certain system-specific options that not all POSIX systems support. Since these options are provided in the kernel, not in the library, simply using the GNU C library does not guarantee any of these features is supported; it depends on the system you are using.
You can test for the availability of a given option using the macros in
this section, together with the function sysconf
. The macros are
defined only if you include `unistd.h'.
For the following macros, if the macro is defined in `unistd.h',
then the option is supported. Otherwise, the option may or may not be
supported; use sysconf
to find out. See section Using sysconf
.
For the following macros, if the macro is defined in `unistd.h',
then its value indicates whether the option is supported. A value of
-1
means no, and any other value means yes. If the macro is not
defined, then the option may or may not be supported; use sysconf
to find out. See section Using sysconf
.
c89
. The GNU C library always defines this
as 1
, on the assumption that you would not have installed it if
you didn't have a C compiler.
fort77
. The GNU C library never
defines this, because we don't know what the system has.
asa
command to interpret Fortran carriage control. The GNU C
library never defines this, because we don't know what the system has.
localedef
command. The GNU C library never defines this, because
we don't know what the system has.
ar
, make
, and strip
. The GNU C library
always defines this as 1
, on the assumption that you had to have
ar
and make
to install the library, and it's unlikely that
strip
would be absent when those are present.
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