On Solaris 10, sed emits an error message if stdin is non-empty but does not end in a newline:

solaris10:~/source/cssc.solaris/releases/1.4.1/CSSC-1.4.1/tests/sact$  env PATH=/usr/ccs/bin:/usr/xpg4/bin:/opt/csw/bin:/usr/bin:/bin  bash -c 'printf "xxx" | sed -e "s/^/# stdout: /"'
sed: Missing newline at end of file standard input.
# stdout: xxx
solaris10:~/source/cssc.solaris/releases/1.4.1/CSSC-1.4.1/tests/sact$  env PATH=/usr/ccs/bin:/usr/xpg4/bin:/opt/csw/bin:/usr/bin:/bin  bash -c 'printf "xxx" | gsed -e "s/^/# stdout: /"'


In the above example, sed was /usr/xpg4/bin/sed.

We should either ensure that sed's input always ends with newline, or find and use GNU sed.