LaTeX is more than a markup language, it allows great flexibility when compiling your documents. One example is the ability for your code and the packages you include to call other utilities installed on your computer to carry out various tasks. This is achieved by including
in the LaTeX code that allows the code to launch external binaries. Packages such as epstopdf, minted, gnuplot, etc. use this facility. To provide additional security, LaTeX requires
-shell-escape be specified on the command line. In Texpad, this amounts to switching the option Shell Escape on in the typeset configuration from the toolbar of an open project.
Shell escape allows for execution of arbitrary code during typesetting, which is a potential, but serious, security hole. Please use this sparingly and only with packages you trust.
Texpad’s auto-sense typesetting is capable of enabling this feature when necessary. You can however override this by configuring the “Shell Escape security policy for Autosense” in the Typesetting pane of your Preferences.