fork vs exec
fork starts a new process which is a copy of the one that calls it, while exec replaces the current process image with another (different) one. Both parent and child processes are executed simultaneously in case of fork() while Control never returns to the original program unless there is an exec() error.In computing, exec is a functionality of an operating system that runs an executable file in the context of an already existing process, replacing the previous executable. This act is also referred to as an overlay. It is especially important in Unix-like systems, although it also exists elsewhere.So when a command is fired from a shell, fork() inherits a child process of it and exec() loads the child process to the memory and executes. Not quite. fork() clones the current process, creating an identical child. exec() loads a new program into the current process, replacing the existing one.
Can you exec without fork : Some programs do exec() without fork() for modifying environment in which new program must be executed. For example nohup. So fork/vfork creates a new process, then exec runs a new executable using that process id.
Why fork () and exec () are used
The exec call is a way to basically replace the entire current process with a new program. It loads the program into the current process space and runs it from the entry point. So, fork and exec are often used in sequence to get a new program running as a child of a current process.
What happens if you call exec () before fork () : A program that calls exec() without fork() is chain loading, overlaying its process with a different program image. There is a whole subculture of chain loading utilities that do particular things to process state and then execute another program to run with that revised process state.
They are use together to create a new child process. First, calling fork creates a copy of the current process (the child process). Then, exec is called from within the child process to "replace" the copy of the parent process with the new process.
The biggest security risk associated with eval() and exec() is that they can be used to execute malicious code. If you pass untrusted input to these functions, it could be used to execute arbitrary code on your system. This could lead to data loss, system damage, or even remote code execution.
What happens if exec is called after fork
exec will replace the contents of the currently running process with the information from a program binary. Thus the process the shell follows when launching a new program is to firstly fork , creating a new process, and then exec (i.e. load into memory and execute) the program binary it is supposed to run.Security Concerns
Since eval() can evaluate any expression, it may execute malicious code if not used carefully. Therefore, it should be avoided when handling untrusted input. On the other hand, exec() is generally considered safer because it executes an entire block of code.The exec() function supports the dynamic execution of Python code. The exec() function can be dangerous if it is used to execute dynamic content (non-literal content). If this dynamic content has an input controllable by a user, it can cause a code injection vulnerability.
If you run eval() with a string that could be affected by a malicious party, you may end up running malicious code on the user's machine with the permissions of your webpage / extension.
Is using exec in Python bad practice : In general, it is best to avoid using eval() and exec() in Python. If you do need to use them, be sure to take steps to mitigate the security risks involved. Here are some additional tips for using eval() and exec() safely: Only pass trusted input to these functions.
Is exec in Python safe : The exec() function supports the dynamic execution of Python code. The exec() function can be dangerous if it is used to execute dynamic content (non-literal content). If this dynamic content has an input controllable by a user, it can cause a code injection vulnerability.
Why is eval evil
eval() is evil if running on the server using input submitted by a client that was not created by the developer or that was not sanitized by the developer. eval() is not evil if running on the client, even if using unsanitized input crafted by the client.
eval(): This function was used to evaluate a string as JavaScript code, but it is now considered deprecated because it can introduce security vulnerabilities and is often unnecessary.Python's built-in exec() function allows you to execute arbitrary Python code from a string or compiled code input. The exec() function can be handy when you need to run dynamically generated Python code, but it can be pretty dangerous if you use it carelessly.
Why is using the eval and exec functions a bad practice and may cause a security issue : eval() is considered insecure because it allows you (or your users) to dynamically execute arbitrary Python code. This is considered bad programming practice because the code that you're reading (or writing) is not the code that you'll execute.