(autoconf.info)Multiple Cases

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5.7 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)