Recipe 19.5. Executing Commands Without Shell Escapes

19.5.1. Problem

You need to use a user's input as part of a command, but you don't want to allow the user to trick the shell into running other commands or looking at other files. If you just blindly call the system function or backticks on a single string containing a command line derived from untested user input, the shell might be used to run the command. This would be unsafe.

19.5.2. Solution

Unlike its single-argument version, the list form of the system function is safe from shell escapes. When the command's arguments involve user input from a form, never use this: