I note that <system.h> is a non-standard header; I replaced it with <unistd.h> and the code compiled cleanly. When the output of your program is going to a terminal (screen), it is line buffered. When the output of your program goes to a pipe, it is fully buffered. You can control the buffering mode by … Read more
A fork gives you a brand new process, which is a copy of the current process, with the same code segments. As the memory image changes (typically this is due to different behavior of the two processes) you get a separation of the memory images (Copy On Write), however the executable code remains the same. … Read more
fork() is how you create new processes in Unix. When you call fork, you’re creating a copy of your own process that has its own address space. This allows multiple tasks to run independently of one another as though they each had the full memory of the machine to themselves. Here are some example usages … Read more
There are two approaches: shmget and mmap. I’ll talk about mmap, since it’s more modern and flexible, but you can take a look at man shmget (or this tutorial) if you’d rather use the old-style tools. The mmap() function can be used to allocate memory buffers with highly customizable parameters to control access and permissions, … Read more
Cygwin has fully featured fork() on Windows. Thus if using Cygwin is acceptable for you, then the problem is solved in the case performance is not an issue. Otherwise you can take a look at how Cygwin implements fork(). From a quite old Cygwin’s architecture doc: 5.6. Process Creation The fork call in Cygwin is … Read more
The fork() primitive often stretches the imagination. Until you get a feel for it, you should trace out on paper what each operation is and account for the number of processes. Don’t forget that fork() creates a near-perfect copy of the current process. The most significant difference (for most purposes) is that fork()‘s return value … Read more
I was trying to understand the double fork and stumbled upon this question here. After a lot of research this is what I figured out. Hopefully it will help clarify things better for anyone who has the same question. In Unix every process belongs to a group which in turn belongs to a session. Here … Read more
The use of fork and exec exemplifies the spirit of UNIX in that it provides a very simple way to start new processes. The fork call basically makes a duplicate of the current process, identical in almost every way. Not everything is copied over (for example, resource limits in some implementations) but the idea is … Read more
Child can ask kernel to deliver SIGHUP (or other signal) when parent dies by specifying option PR_SET_PDEATHSIG in prctl() syscall like this: prctl(PR_SET_PDEATHSIG, SIGHUP); See man 2 prctl for details. Edit: This is Linux-only
vfork() is an obsolete optimization. Before good memory management, fork() made a full copy of the parent’s memory, so it was pretty expensive. since in many cases a fork() was followed by exec(), which discards the current memory map and creates a new one, it was a needless expense. Nowadays, fork() doesn’t copy the memory; … Read more