I stumbled upon an example, which needed to be compiled with the additional option --shell-escape. Using this option it worked just fine, but I'm curious:
Why or when is this option needed and what does it actually do?
1 Answer
Sometimes, it is useful to be able to run external commands from inside the tex file : it allows for example to externalize some typesetting, or to use external tools like bibtex. This is available via the \write18 tex primitive.
The problem is that it allows for almost everything. A tex file is meant to be portable, and one shouldn't have to fear any security issue when compiling a third-party file. So by default, this primitive is disabled.
If an user needs to use it, he needs to explicitely tell the compiler that he trusts the author of the file with shell interaction, and that's exactly the point of the optional --shell-escape argument.
answered Dec 31, 2012 at 10:50
-
1Can you please provide a working example where we can see how is this command written inside a LaTeX document? I would really appreciate it. Commented Jun 29, 2016 at 15:21
-
1You can for example see the end of the last snippet in this answer where they use
\write18to compile a.texinto.dviand convert the.dvito.psto.pdf. Commented Jun 29, 2016 at 19:44
\immediate&\write18and how does one use them?? In short: “No\write18without--shell-escape(minus a few safe exceptions).”-shell-escapeor--shell-escapefor TeXLive or-enable-write18or--enable-write18for MikTeX does the same thing.--shell-escapeis such way that it would be obvious to non-experienced users.