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=========================================
Reading/Writing From File or Stdin/Stdout
=========================================
In many CLI applications, it's common to be able to read from a file or stdin, and write to a file or stdout.
This allows for the chaining of many CLI applications via pipes ``|``.
The following code demonstrates how to do this with Cyclopts:
.. code-block:: python
import sys
from cyclopts import App
from pathlib import Path
from typing import Optional
def read_str(input_: Optional[Path]) -> str:
return sys.stdin.read() if input_ is None else input_.read_text()
def write_str(output: Optional[Path], data: str):
sys.stdout.write(data) if output is None else output.write_text(data)
def read_bytes(input_: Optional[Path]) -> bytes:
return sys.stdin.buffer.read() if input_ is None else input_.read_bytes()
def write_bytes(output: Optional[Path], data: bytes):
sys.stdout.buffer.write(data) if output is None else output.write_bytes(data)
app = App()
@app.default
def scream(input_: Optional[Path] = None, output_: Optional[Path] = None):
"""Uppercase all input data.
Parameters
----------
input_ : Optional[Path]
If provided, read data from file. If not provided, read from stdin.
output_ : Optional[Path]
If provided, write data to file. If not provided, write to stdout.
"""
data = read_str(input_)
processed = data.upper()
write_str(output_, processed)
if __name__ == "__main__":
app()
.. code-block:: console
$ echo "hello cyclopts users." > demo.txt
$ python scream.py demo.txt
HELLO CYCLOPTS USERS.
$ python scream.py demo.txt output.txt
$ cat output.txt
HELLO CYCLOPTS USERS.
$ echo "foo" | python scream.py
FOO
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