I experienced some difficulty installing clientsdk.2.81.UC2.LINUX.tar on
a Slackware release 9.1 system with the GNU version of the cpio utility
but have (finally) determined both the problem and the fix:

Embedded in the install scripts is

cpio -icdBum ... < $file

These command line options do not work with GNU cpio (or, at least, GNU
cpio version 2.5). Command line options that do work are

cpio -idv ... < $file

Attempting to execute installclientsdk without editing it and the
install_gls, install_msg, and installesql scripts will result in strange
(and inaccurate) error messages about being out of disk space in
/tmp/install.

After doing this I was able to install the upgrade (for GNU gcc 3.2.x)
and ESQL/C programs now compile and execute as they should; i.e., no
"errno" problems, no shared library problems.

Hope this helps somebody.

YMMV