PipePy to function

The function's arguments must be either: - a subset of returncode, output, errors, or - a subset of stdout, stderr

Argument ordering is irrelevant — the function's signature is inspected to assign values.

Using output (waited execution)

In the first case, the command is waited for and its evaluated output is passed to the function.

from pipepy import wc

def lines(output):
    for line in output.splitlines():
        try:
            lines, words, chars, filename = line.split()
        except ValueError:
            continue
        print(f"File {filename} has {lines} lines, "
              f"{words} words and {chars} characters")

wc('*') | lines

Using stdout/stderr (streaming execution)

In the second case, the command and the function execute in parallel. The command's stdout and stderr are streamed to the function.

import re
from pipepy import ping

def mean_ping(stdout):
    pings = []
    for line in stdout:
        match = re.search(r'time=([\d\.]+) ms$', line.strip())
        if not match:
            continue
        time = float(match.groups()[0])
        pings.append(time)
        if len(pings) % 10 == 0:
            print(f"Mean time is {sum(pings) / len(pings)} ms")

ping('-c', 30, "google.com") | mean_ping

If the command ends before the function, next(stdout) raises StopIteration. If the function ends before the command, the command's stdin is closed.

Generator functions

The function can include yield and return a generator that can be piped into another command:

from pipepy import cat, grep

def my_input():
    yield "line one\n"
    yield "line two\n"
    yield "line two\n"
    yield "something else\n"
    yield "line three\n"

def my_output(stdout):
    for line in stdout:
        yield line.upper()

print(my_input() | cat | grep('line') | my_output | grep("TWO"))
# <<< LINE TWO
# ... LINE TWO