Package: slime Version: 1:20070927-2 Severity: normal sh points to dash and the following is displayed during an installation (with apt): $ apt install <something> ... install/slime: Handling install for emacsen flavor emacs21 [: 44: ==: unexpected operator rm: cannot remove `/usr/share/emacs21/site-lisp/slime/ChangeLog': No such file or directory [: 55: ==: unexpected operator Loading 00debian-vars... ... $ grep -C3 == /usr/lib/emacsen-common/packages/install/slime # in case of a failed installation .el symlinks are left behind, remove them if [ -d "${ELCDIR}" ] ; then if [ "${ELCDIR}" == "" ] ; then echo ELCDIR is empty, emergency stop exit 1 else -- fi if [ -d "${ELCDIR}/contrib" ] ; then if [ "${ELCDIR}" == "" ] ; then echo ELCDIR is empty, emergency stop exit 1 else == is not an operator for /usr/bin/[. It is one for the bash keyword [[. [ after an if in bash probably also is interpreted directly by bash.