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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 .
The jobs command will list the background jobs existing in the job table, along with their job number and job state (stopped or running). When a session ends when the user logs out (exits the shell, which terminates the session leader process), the shell process sends SIGHUP to all jobs, and waits for the process groups to end before ...
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.
Shellshock, also known as Bashdoor, [1] is a family of security bugs [2] in the Unix Bash shell, the first of which was disclosed on 24 September 2014.Shellshock could enable an attacker to cause Bash to execute arbitrary commands and gain unauthorized access [3] to many Internet-facing services, such as web servers, that use Bash to process requests.
To remove zombies from a system, the SIGCHLD signal can be sent to the parent manually, using the kill command. If the parent process still refuses to reap the zombie, and if it would be fine to terminate the parent process, the next step can be to remove the parent process. When a process loses its parent, init becomes its new parent.
As long as the system is responsive, infinite loops can often be interrupted by sending a signal to the process (such as SIGINT in Unix), or an interrupt to the processor, causing the current process to be aborted. This can be done in a task manager, in a terminal with the Control-C command, [9] or by using the kill command or system call.
Some shells (e.g. bash) provide a shell builtin that may be used to prevent SIGHUP being sent or propagated to existing jobs, even if they were not started with nohup. In bash, this can be obtained by using disown-h job; using the same builtin without arguments removes the job from the job table, which also implies that the job will not receive the signal.
The command killall -9 has a similar, while dangerous effect, when executed e.g. in Linux; it does not let programs save unsaved data. It has other options, and with none, uses the safer SIGTERM signal. SIGPIPE The SIGPIPE signal is sent to a process when it attempts to write to a pipe without a process connected to the other end. SIGPOLL