operating-system - Row Coding

Is there a Python equivalent to the ‘which’ command [duplicate]

Python 3.3 added shutil.which() to provide a cross-platform means of discovering executables: http://docs.python.org/3.3/library/shutil.html#shutil.which Return the path to an executable which would be run if the given cmd was called. If no cmd would be called, return None. Sample calls: >>> shutil.which(“python”) ‘/usr/local/bin/python’ >>> shutil.which(“python”) ‘C:\\Python33\\python.EXE’ Unfortunately, this has not been backported to 2.7.x.

When should the option RemainAfterExit needs to be set true when creating new systemd services?

by Tarik

Use RemainAfterExit=yes for services, which somehow change state of the system. When you want that state reverted, you just stop the service. Then you can start it again, but not without first stopping it. An example would be service which creates a flag in filesystem to be used by some other application. When started, it …

Try catch with locks in C++

by Tarik

For this we use the RAII-style construct std::lock_guard. When you use std::mutex m; { // start of some scope std::lock_guard lg(m); // stuff } // end of scope lg will ensure that m will be unlocked no matter what path the scope is left as it is destroyed at scope exit and std::lock_guards destructor will …

Difference between physical/logical/virtual memory address

by Tarik

My answer is true for Intel CPUs running on a modern Linux system, and I am speaking about user-level processes, not kernel code. Still, I think it’ll give you some insight enough to think about the other possibilities Address Types Regarding question 3: I have come across discussion that virtual and logical addresses/address space are …

ExitCodes bigger than 255, possible?

by Tarik

Using wait() or waitpid() It is not possible on Unix and derivatives using POSIX functions like wait() and waitpid(). The exit status information returned consists of two 8-bit fields, one containing the exit status, and the other containing information about the cause of death (0 implying orderly exit under program control, other values indicating that …

I/O concept flush vs sync

by Tarik

In Java, the flush() method is used in output streams and writers to ensure that buffered data is written out. However, according to the Javadocs: If the intended destination of this stream is an abstraction provided by the underlying operating system, for example a file, then flushing the stream guarantees only that bytes previously written …

Is it possible to create an operating system using Python? [closed]

by Tarik

Unfortunately Python is classified as a very high level programming language. It cannot be used, for example, to directly access hardware and perform low-level data structure manipulation. It is completely dependent on something to abstract the hardware from it, and that is the Kernel. It is, however, technically possible to create an operating system centered …

What is the correct way to detect if ruby is running on Windows?

by Tarik

It turns out, there’s this way: Gem.win_platform?

Why does a 32-bit OS support 4 GB of RAM?

by Tarik

Because 32 bits are able to represent numbers up to 232 − 1 = 4294967295 = 4 GiB − 1 and therefore address up to 232 individual bytes which would be 4 GiB then. There are ways to circumvent that, though. For example using PAE even a 32-bit operating system can support more memory. Historically …

How is sleep implemented at the OS level?

by Tarik

Sleep() is implemented at the OS level. The processor doesn’t spin when a task/thread/process is sleeping. That particular thread is put on a pending queue (the thread isn’t ready to run) until the time has expired at which point the thread will be placed on the ready to run queue. In the meantime, other threads …