When I try to use echo "#!/bin/sh" >> /tmp/missing/semester, something strange occured, after I typed echo "#!/bin/sh" then I press the space key and found I cannot enter any more character with the following prompt:
When we type commands in shell, the first word is seen as the name of executable (if it is not absolute or relative path，shell will seek it in system path). However, we know that the semester script is not executable from the permissions listed above while sh is executable we can found in system path. For sh to "execute" the script, it only needs to be able to read the file.
