A small utility library to handle arguments and read/write text to files using bash-like syntax
Requires python3.7+
To install with pip, run:
pip install bash_like
This creates small helper function/symbols to handle some common patterns when creating python scripts
To use, include the following imports at the top:
from bash_like import S, SO # (Shell, ShellOperations)| Description | Bash | bash_like (python) |
|---|---|---|
| Write a string to a file | echo hello > file.txt |
S("hello\n") > "file.txt" |
| Append to file | echo hello >> file.txt |
S("hello\n") >> "file.txt" |
| Print to STDERR (2) | echo error 1>&2 |
S("error\n") > 2 |
| Print to STDOUT (1) | echo hello |
S("hello\n") > 1 |
| Read text from a file | <input.txt |
SO < "input.txt" |
| Read lines from a file (strips, and ignores empty lines) | while read line; do echo line; done <input.txt |
SO << "input.txt" |
| Get Environment or CLI argument, If not present, print error and exit | FILE="${1:?Provide file as first CLI arg}" ;VAL="${CONFIG_VAR:?Error - CONFIG_VAR is not set}" |
file = SO | (1, "Provide file as first CLI arg"); val = SO | ("CONFIG_VAR", "Error - CONFIG_VAR is not set") |
| Get Environment or CLI argument, If not present, use default | FILE="${1:-output.txt}"; VAL="${DIFFERENCE:-5}" |
file = SO - (1, "output.txt"); val = SO - ("DIFFERENCE", 5) |
Of course, you don't have to use hello for the strings, wrapping any python string in S allows you to quickly redirect it to a file, without having to do the with block:
As a more complete example, this takes a file as input, and writes the contents of that file in lower case to ${APP_DATA:-$HOME/.local/share}/..... It:
- uses the first CLI argument as the input file, else prints an error and exits
- uses the second CLI argument as basename, else defaults to
output.txt - uses
APP_DATA(some environment variable for your application) if present, else defaults to~/.local/share
APP_DATA=~/.local/appdata python3 main.py input.txt fout.txt would write to ~/.local/appdata/fout.txt
from os import path, environ
from time import time
from bash_like import S, SO
# the 1 and 2 correspond to sys.argv[1] and sys.argv[2], if they're present
inp = SO | (1, "Error: no input file provided as first argument")
out = SO - (2, "output.txt")
app_data = SO - ("APP_DATA", path.join(environ["HOME"], ".local", "share"))
# read file, casefold (lowercase), and write to file
S((SO < inp).casefold()) > path.join(app_data, out)
# append current time to a temporary logfile
S(f"{time()}\n") >> "/tmp/time.log"