Write a python script to display the contents of a file to stdout

You can do

import fileinput

with fileinput.input() as f_input:
    for line in f_input:
        print(line, end='')

If you save this script as filein.py and make it executable, you can do all of the following and get the expected output:

$ ls | ./filein.py          # Prints a directory listing to stdout.
$ ./filein.py /etc/passwd   # Reads /etc/passwd to stdout.
$ ./filein.py < /etc/passwd # Reads /etc/passwd to stdout.

If you want to print the filename and line number along with the contents, you can use

import fileinput

with fileinput.input() as f:
    for line in f:
        print(f.filename(), f.lineno(), line, end='')

Credits:- I found these two tips in Python Cookbook by David Beazley, Brian K Jones, 3rd edition, published in 2013 → Chapter 13 → pg 539-540.

See also:

• https://stackoverflow.com/a/78991782 - my answer to the same question on stackoverflow.
• https://docs.python.org/3/library/fileinput.html

python -c "import fileinput; print(''.join(fileinput.input()), end='')"

For example

$ ls | python -c "import fileinput; print(''.join(fileinput.input()), end='')"              # Prints a directory listing to stdout.
$ python -c "import fileinput; print(''.join(fileinput.input()), end='')" /etc/passwd       # Reads /etc/passwd to stdout.
$ python -c "import fileinput; print(''.join(fileinput.input()), end='')" < /etc/passwd     # Reads /etc/passwd to stdout.