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(autoconf.info)Multiple Cases

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Multiple Cases
==============

   Some operations are accomplished in several possible ways, depending
on the UNIX variant.  Checking for them essentially requires a "case
statement".  Autoconf does not directly provide one; however, it is
easy to simulate by using a shell variable to keep track of whether a
way to perform the operation has been found yet.

   Here is an example that uses the shell variable `fstype' to keep
track of whether the remaining cases need to be checked.

     AC_MSG_CHECKING(how to get filesystem type)
     fstype=no
     # The order of these tests is important.
     AC_TRY_CPP([#include <sys/statvfs.h>
     #include <sys/fstyp.h>], AC_DEFINE(FSTYPE_STATVFS) fstype=SVR4)
     if test $fstype = no; then
     AC_TRY_CPP([#include <sys/statfs.h>
     #include <sys/fstyp.h>], AC_DEFINE(FSTYPE_USG_STATFS) fstype=SVR3)
     fi
     if test $fstype = no; then
     AC_TRY_CPP([#include <sys/statfs.h>
     #include <sys/vmount.h>], AC_DEFINE(FSTYPE_AIX_STATFS) fstype=AIX)
     fi
     # (more cases omitted here)
     AC_MSG_RESULT($fstype)