General information: what is shell escape?
A number of LaTeX packages need to use external tools to function. Such a tool is called from the LaTeX source code using a system command. However, by default the unrestricted use of external system calls is not permitted by LaTeX. This is a security measure to prevent malicious LaTeX code to delete files, change system settings, allow remote access, et cetera. Therefore, when you try to compile a document using default settings, you will get an error message and/or wrong output if you use a package that needs an external tool.
To be able to use such packages you can change the security settings for the current document. This is done by using a compiler flag called
shell-escape. Note that this introduces the risks outlined above, so you should only use this flag if you trust the source code that you are trying to compile.
Some example packages that use shell escape:
- tikz (externalize)
- standalone (convert option)
- pgfplots (gnuplot)
The default setting is usually "Restricted Shell escape" this allows a small number of programs to be called by default (in a restricted form that does not allow shell redirection) these are (in a default TeX Live 2021 configuration)
If you do not want to allow even these programs to run, then you can use the option
in all the ways described for
To check if the shell-escape mechanism is active, you can use this small document (taken from here), but slightly changed so that it produces output --- log messages are often hidden in some editor/integrated environments):
No shell escape\or
Unrestricted shell escape\or
Restricted shell escape%
It will create a document with the current shell escape setting displayed.