Advanced programming in unix.pptx
- 1. Advanced programming in unix Presentation on Environmental various processes limits at exit and vfork
- 2. Environmental process limits refer to the maximum resources that a process can use in the system. These limits are set by the operating system to prevent a single process from consuming too many resources and causing other processes to fail. There are various types of process limits that can be set, including: # Memory limit: This limit restricts the amount of memory that a process can allocate. # File size limit: This limit restricts the maximum size of a file that a process can create. # Open file limit: This limit restricts the number of files that a process can have open simultaneously. # Process limit: This limit restricts the maximum number of processes that a user can create. These limits can vary depending on the operating system and the system configuration. When a process reaches its environmental limits, it may fail or be terminated by the operating system. ENVIRONMENTAL VARIOUS PROCESS LIMITS AT EXIT AND VFORK
- 3. Two system calls in Unix-like operating systems, namely exit() and vfork(). The exit () system call is used to terminate the calling process, and it is commonly used to return a value from a program or signal its termination to the parent process. On the other hand, vfork() creates a new process by duplicating the calling process, but it does not fully copy the process address space. Instead, it shares the address space between the parent and child processes until the child process calls execve() or exit(). This allows for more efficient creation of new processes with minimal overhead. Regarding environmental and process limits, both exit() and vfork() may have limits on the resources they can use, such as memory or CPU time. These limits may be set by the operating system or by the user through configuration files or command-line options. It is important to consider these limits when using these system calls to avoid exceeding them and potentially causing errors or crashes.
- 4. Environmental various processes limits at exit When a process reaches its limit, it may exit or terminate. This can happen if the process runs out of memory or exceeds its CPU time limit. When a process exits due to environmental limits, it may return an error code indicating the specific limit that was reached. In advanced programming, it is important to handle these errors and gracefully exit the program when necessary. This can involve freeing up resources and closing open files or network connections before exiting. It is also important to monitor the system's resource usage and adjust the process limits as needed to prevent issues from arising. Overall, understanding and managing environmental limits is an important part of advanced programming and system administration. By properly managing these limits, developers can create more efficient and reliable software that works well within the constraints of the system.
- 5. Exit function -Normal termination *Return from main *Calling exit-including calling exit handlers *Calling –exit or-exit. Its called by exit function -Abnormal termination *Calling abort *Receiving some signals. -Special cases *Overhanded process #If the parent of a process terminates before it does; that process becomes an overhead *Zombie process #Child termination but parent has not yet called the wait or wait pid function to return its status
- 6. Environmental various processes limits at vfork These limits refer to the constraints that are imposed on a process by its environment, such as the operating system or hardware. These constraints may include limits on the amount of memory or CPU time that a process can use, as well as limits on the number of open files or network connections. These limits are put in place to ensure that a process does not consume too many resources and cause problems for other processes or the system as a whole. System administrators can adjust these limits to balance the needs of different processes and ensure that the system runs smoothly.
- 7. Role Used to create a new process Characteristics The call sequence and the return value are the same as the fork; *Vfork a child process that does not completely replicate the address space of the parent process to the child process, because the child process calls exec (or exit) immediately, so it needs to access the address space. But before the child process calls exec (or exit), it runs in the space of the parent process; *Vfork guarantees that the child process runs first, and the parent process runs when the child process finishes executing exec (or exit). However, this can cause deadlocks, for example, a child process that relies on the parent process for further action; Creates new processes with the express purpose of executing a new program. New child process runs in parents address space until exec or exit is called. V fork guarantees that the child will run before the parent until exec or exit all is reached.