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XFL Stages

This document lists a number of POSIX Pipelines stages which must be included in a basic implementation.

XFL Stages

The currently available stages are listed here in no particular order.

  • buffer

Use the buffer stage to hold all input records until the source stage terminates.

  • console

The console stage is so named for compatibility with CMS/TSO Pipelines. In POSIX Pipelines, console serves as a gateway between shell pipes and POSIX Pipelines stages.

When console is the first stage of a pipeline, it reads lines of text from file descriptor zero (0) delimited by newline characters. In this mode, its output must be connected to another POSIX Pipelines stage and its output is records with newline characters removed. Output records are bounded where newlines occur on input.

When console is NOT the first stage of a pipeline, its input must be connected to another POSIX Pipelines stage. It then reads input records and writes to file descriptor one (1) with newline characters appended to each line. In this mode, console may also be connected on output to a following POSIX Pipelines stage to which it will write the input records unaltered. (No newline inserted.)

  • cp

Use the cp stage to issue VM (CP) commands and recover their output.

This stage requires the z/VM hypervisor. It really only works on z/Linux when hosted by z/VM.

This stage requires privileges. Usually, one must be root to issue CP commands.

  • fanin

Use the fanin stage to collect multiple input streams into a single output.

  • filer, aliased as "<"

Use < to read from a file.

  • filew, aliased as ">"

Use > to write to a file.

  • literal

Use the literal stage to insert a line of literal text into a stream.

  • locate

Use the locate stage to find occurrences of the specified string in the input stream.

  • strliteral

Use the strliteral stage to insert a line of literal text into a stream.

XFL Stage Operation

Stages run as independent programs.
They inherit open file descriptors which are described in an inherited environment variable and then use peekto(), output(), and readto() functions to process incoming and outgoing records.