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wait normally returns the exit status of the last job which terminated. It may also return 127 in the event that n specifies a non-existent job or zero if there were no jobs to wait for. Because wait needs to be aware of the job table of the current shell execution environment, it is usually implemented as a shell builtin .
Command-line completion generally only works in interactive mode. That is, it cannot be invoked to complete partially typed commands in scripts or batch files, even if the completion is unambiguous. The name tab completion comes from the fact that command-line completion is often invoked by pressing the tab key.
This is a list of POSIX (Portable Operating System Interface) commands as specified by IEEE Std 1003.1-2024, which is part of the Single UNIX Specification (SUS). These commands can be found on Unix operating systems and most Unix-like operating systems.
In particular, the POSIX specification and the Linux man page signal (7) require that all system functions directly or indirectly called from a signal function are async-signal safe. [6] [7] The signal-safety(7) man page gives a list of such async-signal safe system functions (practically the system calls), otherwise it is an undefined behavior ...
If a process in the "running" state needs to wait for a resource (wait for user input or file to open, for example), it is assigned the "blocked" state. The process state is changed back to "waiting" when the process no longer needs to wait (in a blocked state). Once the process finishes execution, or is terminated by the operating system, it ...
In Unix and Unix-like operating systems, job control refers to control of jobs by a shell, especially interactively, where a "job" is a shell's representation for a process group. Basic job control features are the suspending, resuming, or terminating of all processes in the job/process group; more advanced features can be performed by sending ...
The last string is the command that started the process. The state of a process can be changed using various commands. The fg command brings a process to the foreground, while bg sets a stopped process running in the background. bg and fg can take a job id as their first argument, to specify the process to act on.
In computer science and software engineering, busy-waiting, busy-looping or spinning is a technique in which a process repeatedly checks to see if a condition is true, such as whether keyboard input or a lock is available. Spinning can also be used to generate an arbitrary time delay, a technique that was necessary on systems that lacked a ...