Writing Python Conditionals For Crontab

How does a python if statement work when editing it in crontab? Using python 3.6.3 Using linux crontab I am trying to get a count of the amount of hidden files within a directory

Solution 1:

A much better solution is to avoid a subprocess entirely. (And even if you use a subprocess, don't use ls in scripts.)

from pathlib import Path

dotfiles = Path().glob('.[!.]*')
iflen(list(dotfiles)) > 0:
    do_things()

Actually, there is no real need to check the length; you can say

dotfiles = list(Path().glob('.[!.]*'))
if dotfiles:
    do_things('The files which matched are %s' % dotfiles)

Somewhat obscurely, but more succinctly, you could iterate over the generator instead; the loop body will be executed only if there is at least one file which matches. This is an optimization if you only care whether there is at least one file, as it stops once it finds the first one;

for file in Path().glob('.[!.]*'):
    do_things()
    break

Python doesn't care whether you run your script from cron or not (though sometimes you need to arrange the environment for Python in your cron job if you have libraries installed in nonstandard locations). But why are you using Python at all here if all your business logic is in shell scripts? (Though your shell scripting could also benefit from studying some antipatterns to avoid.)

Here's the whole thing entirely in shell script, using similar logic:

for file in .[!.]*; dotest -e "$file" || break# cf nullgbob
    executeAlert.sh
    breakdone

Bash offers shopt -s nullglob to avoid entering the loop if the wildcard has no match; but cron runs sh and it's not altogether hard to avoid bashisms here (though the globbing behavior in the case of no matches is surprising).

If you want all the matches in a shell script, you can say

set -- .[!.]*
if [ "$@" != ".[!.]*" ]; then
    executeAlert.sh "$@"# argument is list of matching filesfi

If you use Bash or ksh, you could collect the matches into an array;

shopt -s nullglob
dotfiles=(.[!.]*)
for file in"${dotfiles[@]}"; doecho"Here's one dotfile: $file"doneif [[ "${#dotfiles[@]}" > 0 ]]; then
     executeAlert.sh "${dotfiles[@]}"fi

Your egrep regex would only match on dot directories; I have assumed that this was a mistake.

Solution 2:

printing res.stdout will show you that it has an endline character within it.

>>>res.stdout'0\n'

so just strip the '\n' character:

res = res.stdout.strip('\n')
ifres== "0":
    (executeAlert.sh script)

Alternatively, just cast it as an integer:

ifint(res.stdout)== 0:
    (executeAlert.sh script)