#! /bin/sh

# Use df to find a writable directory on a file system different from that
# of the current directory.  If one is found, create a temporary directory
# inside it.

: ${DF=df}
: ${MKDIR=mkdir}

# Try these:
candidate_tmp_dirs="
 $TMPDIR
 /tmp
 /var/tmp
 /usr/tmp
 $HOME
"

other_partition_tmpdir=

# WARNING: using sed like this to extract the mount point will fail
# if the mount point name contains `% '.
dot_mount_point=`$DF --no-sync -P . | sed -n '2s/.*%  *//p'`
for d in $candidate_tmp_dirs; do
  d_mount_point=`$DF --no-sync -P $d | sed -n '2s/.*%  *//p'`

  # Same partition?  Skip it.
  test x$d_mount_point = x$dot_mount_point && continue

  # See if we can create a directory in it.
  if $MKDIR "$d/df-$$" > /dev/null 2>&1; then
    other_partition_tmpdir="$d/df-$$"
    break
  fi

done