python - crontab some commands works, others do not

Question

Summary

I've got a python script that writes a row to a sqlite3 database. I would like to run it with crontab, but can't get it working.

What I've tried so far

crontab -l                
* * * * * /opt/homebrew/bin/python3 /Users/natemcintosh/dev/battery_condition/get_battery_condition.py 
* * * * * /opt/homebrew/bin/python3 /Users/natemcintosh/dev/battery_condition/testing_cron.py

The first command is the one that appends to the database row. I can copy and paste that command at the command line, run it, and it adds the row. It does not run every minute. The contents of /Users/natemcintosh/dev/battery_condition/get_battery_condition.py are

# /Users/natemcintosh/dev/battery_condition/get_battery_condition.py
import subprocess
import re
import sqlite3
import datetime


def get_conds():
    # Run the command to get battery info
    command = "system_profiler SPPowerDataType".split()
    response = subprocess.run(command, check=True, capture_output=True)
    response = str(response.stdout)

    # Get just the parts of interest
    cycle_count = re.findall(r"Cycle Count: (d+)", response)[0]
    condition = re.findall(r"Condition: (w+)", response)[0]
    max_capacity = re.findall(r"Maximum Capacity: (d+)", response)[0]
    now = str(datetime.datetime.now().isoformat())

    return [now, cycle_count, condition, max_capacity]


def append_row_to_db(db_name: str, items: list):
    conn = sqlite3.connect(db_name)
    with conn:
        conn.execute("INSERT INTO battery_condition VALUES (?,?,?,?)", items)
    conn.close()


if __name__ == "__main__":
    # Get the condition
    battery_condition = get_conds()

    # Append to the file
    filename = "/Users/natemcintosh/dev/battery_condition/battery_condition.db"
    append_row_to_db(filename, battery_condition)

The second command is a test script that does work.

#/Users/natemcintosh/dev/battery_condition/testing_cron.py
import datetime

if __name__ == "__main__":
    with open("/Users/natemcintosh/Desktop/crontest.txt", "a+") as f:
        now = str(datetime.datetime.now().isoformat())
        f.write(f"{now}
")

Every minute, a new line appears in /Users/natemcintosh/Desktop/crontest.txt with the current date and time. I've also tried having the test script write to other locations on disk, and they all seem to work.

question from:https://stackoverflow.com/questions/65865053/crontab-some-commands-works-others-do-not

Answer 1

With the help of Gordon Davisson, I've figure out the issue. When I call subprocess.run(command, check=True, capture_output=True), the command did not have the full path to the executable.

It used to be

command = "system_profiler SPPowerDataType".split()

I got the full path to the system_profiler command with

$ which system_profiler
/usr/sbin/system_profiler

And fixed the line in my python script to be

command = "/usr/sbin/system_profiler SPPowerDataType".split()

The tool now runs successfully!