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In computing, redirection is a form of interprocess communication, and is a function common to most command-line interpreters, including the various Unix shells that can redirect standard streams to user-specified locations. The concept of redirection is quite old, dating back to the earliest operating systems (OS).
This class of status code indicates the client must take additional action to complete the request. Many of these status codes are used in URL redirection. [2] A user agent may carry out the additional action with no user interaction only if the method used in the second request is GET or HEAD. A user agent may automatically redirect a request.
In computing, the exit status (also exit code or exit value) of a terminated process is an integer number that is made available to its parent process (or caller). In DOS , this may be referred to as an errorlevel .
Standard input is a stream from which a program reads its input data. The program requests data transfers by use of the read operation. Not all programs require stream input.
They are a limited form of inter-process communication (IPC), typically used in Unix, Unix-like, and other POSIX-compliant operating systems. A signal is an asynchronous notification sent to a process or to a specific thread within the same process to notify it of an event.
In Unix-like computer operating systems, a pipeline is a mechanism for inter-process communication using message passing. A pipeline is a set of processes chained together by their standard streams , so that the output text of each process ( stdout ) is passed directly as input ( stdin ) to the next one.
Core dumps are often used to assist in diagnosing and debugging errors in computer programs. On many operating systems, a fatal exception in a program automatically triggers a core dump. By extension, the phrase "to dump core" has come to mean in many cases, any fatal error, regardless of whether a record of the program memory exists.
Unix shells use dup2 for input/output redirection. Along with pipe(), it is a tool on which Unix pipes rely. The following example uses pipe() and dup() in order to connect two separate processes (program1 and program2) using Unix pipes: