I have a while loop that reads data from a child process using blocking I/O by redirecting stdout of the child process to the parent process. Normally, as soon as the child process exits, a blocking read() in this case will return since the pipe that is read from is closed by the child process. Now I have a c…
Tag: fork
fork() – have parent process do work without waiting for child process
I’m making a shell in C for a school project that is capable of running processes in parallel if it is commanded to do so. This is the loop of the shell application that waits for commands: Please do disregard the constants being incremented and decremented. Now, this only works partially. Whenever I gi…
fork: child process doesn’t stay in an infinite loop
In the above code snippet inside if statement if we put while(1), it doesn’t remains blocked and when enter key is pressed program is exited, but in case of parent if we put while(1), parent remains blocked until we give ctrl+c. Please clarify this behaviour of child. Answer In the above code snippet in…
Creating “background running” children with fork() and kill each of them with signals
I need to create n children from the same parent, and have them running while the parent asks infinitely for a signal to send to some child. I made the parent create those n children, but they finished executing, so I made them enter a while(1) loop. The problem is, when I try to kill any child, it becomes a
Change child process’ termination signal at runtime
Using clone() to fork a process you can specify the signal a child process should send its parent on death instead the “normal” SIGCHLD. Is it possible to change the set termination signal after the child was created? Either by the child or the parent? Answer I (quickly) scanned Linux’ sourc…
Can someone please explain how this works?fork(),sleep()
What is happening here? How is sleep() getting executed in the for loop? When is it getting called? Here is the output: Please explain this output. I am not able to understand how it’s working. Step by step analysis would be great. Answer In the first loop, the original (parent) process forks 10 copies …
Father-child process use pipe to talk, hangs after “execlp”, why?
I’ve got a simple text file called “tmp” under current directory, I wish to “cat” this file and then “sort” it, I want to use a c program to act like pipe “|” so I tried to use a father/child talk to do this. Unexpectedly, the program hangs after “ca…
How to forking process in a way such that reaping the child isn’t neccessary
I seem to have a vague memory that some facility in Linux exists that allows one to fork() a process in such a way that the child is automatically reaped by the system without a zombie being created. What is this mechanism? Or is my memory just wrong? Answer The portable way to do this is to double-fork:
Why is sys_fork not used by glibc’s implementation of fork?
In eglibc’s nptl/sysdeps/unix/sysv/linux/i386/fork.c there’s a definition: which is used in actual __libc_fork() as the heart of the implementation. But e.g. in Linux’s arch/x86/entry/syscalls/syscall_32.tbl exists a sys_fork entry, as well as in syscalls_64.tbl. So apparently Linux does hav…
Creating three children in C that have the same parent
My problem is that the children does not have the same parent and does not appear correctly, here is my code: As of right now when i run the program i will get this as output in bash, where bash has the PID of 11446: How do i get the first child to appear first, second child to appear second