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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 .
Microsoft also provides a sleep resource kit tool for Windows which can be used in batch files or the command prompt to pause the execution and wait for some time. [10] Another native version is the timeout command which is part of current versions of Windows.
If the first 0 in the second byte is 0, the value of the second value in the second byte is irrelevant on most processors; however, on the IBM System/360 Model 91, if that value refers to register 15, the instruction will wait for all previously-decoded instructions to complete before continuing.
The pause command in DOS requests the user to "Press any key to continue.". In computing, "Press any key to continue" (or a similar text) was a historically used prompt to the user when it was necessary to pause processing.
In MS-DOS, a batch file can be started from the command-line interface by typing its name, followed by any required parameters and pressing the ↵ Enter key. When DOS loads, the file AUTOEXEC.BAT, when present, is automatically executed, so any commands that need to be run to set up the DOS environment may be placed in this file.
A shell script (or job) can report progress of long running tasks to the interactive user. Unix/Linux systems may offer other tools support using progress indicators from scripts or as standalone-commands, such as the program "pv". [49] These are not integrated features of the shells, however.
In Linux, if the script was executed by a regular user, the shell would attempt to execute the command rm -rf / as a regular user, and the command would fail. However, if the script was executed by the root user, then the command would likely succeed and the filesystem would be erased. It is recommended to use sudo on a per-command basis instead.
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 ...