Processes II and Process Management

Vocabulary terms and definitions related to process creation, synchronization, identification, and termination as covered in the Processes II lecture.

PID (Process Identifier)

A unique number used by the system to identify and manage individual processes.

fork()

A system call that creates a child process by making an exact copy of the parent process; it returns the child's PID to the parent and 0 to the child.

pid_t

A signed integer data type in the GNU C Library (usually an int) capable of representing a process ID.

Race condition

An issue that occurs when two or more operations are executed at the same time, requiring process synchronization to prevent data inconsistency.

Program Counter

The hardware/software mechanism the CPU uses to keep track of which instruction is going to execute next while executing a program sequentially.

wait()

A system call that forces the parent process to suspend execution until its first child process terminates.

waitpid()

A system call that allows a parent to wait for a specific child process identified by a unique PID.

Process suspension

An OS action where a process in main memory is moved to a Suspended state on disk to free memory for another process.

cat /proc/sys/kernel/pid_max

A command used to determine the maximum number of unique PIDs the system supports.

exec() family

A set of system calls used by a child process to execute a different program, common in shell operations.

_exit()

A function used in child processes after an exec() failure to terminate without flushing fully buffered streams (like stdout) to avoid duplicate data output.

SIGCHLD

A signal automatically sent to the parent process when a child process terminates.

Orphan

A child process that is still executing after its parent process has terminated.

Zombie

A terminated child process that still has an entry in the process table because the parent is not currently executing a wait() call.

init process

The system process with PID 1 that adopts orphaned and zombie processes when a parent terminates.

Process group

A logical cluster of processes belonging to the same application or deployment unit used to distribute signals for job control.

setpgid()

A function used to change a process's group to a new value.

Session

A collection of one or more process groups.

getppid()

A function that returns the process ID of the parent of the current process.

getuid()

A function that returns the real user ID of the calling process.

File Descriptors (forked)

Copies of descriptors inherited by the child where the actual R-W pointer is shared between parent and child.

lseek()

A function used to reposition the file offset of an open file description measured in bytes from the beginning of the file.

SIGHUP

A signal sent to each process in an orphaned process group if any group member is stopped when a process terminates.