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A Surprisingly Common Mistake Involving Wildcards & The Find Command (blog.robertelder.org)

submitted 1 week ago* (last edited 1 week ago) by unglueclass23@programming.dev to c/linux@programming.dev

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I came across this older article from 2020 and I found it informative. It's about how the shell does globbing and the potential issues it can cause if not understood correctly.

TLDR:

find . -not -name *.py -delete and find . -not -name '*.py' -delete will behave differently in certain scenarios.

In the first example, the shell will replace the wildcard pattern with a list of matching file names IF there are any matches in the current directory. If there isn't, then it won't do anything and will pass *.py to find.

In the second example, the shell won't do any globbing at all and will just pass *.py

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[–] vk6flab@lemmy.radio 22 points 1 week ago (2 children)

Basic habit to get into:

If you're contemplating doing something destructive, do a dry-run first.

In this case, remove the -delete flag, run the command and see what you get.

A good approach is to build a command step by step and test your assumptions each iteration.

Things might take a few moments longer, but one day it's going to save your bacon.

As for unexpected globbing, learn the difference between quoted and unquoted, and single versus double quotes.

Source: Linux user for 25+ years

[–] unglueclass23@programming.dev 4 points 1 week ago (2 children)

What's the difference between single vs double quotes?

[–] IanTwenty@piefed.social 11 points 1 week ago* (last edited 1 week ago)

Presuming BASH:

https://www.gnu.org/software/bash/manual/bash.html#Quoting

Single quotes are much safer/predictable because:

Enclosing characters in single quotes (‘'’) preserves the literal value of each character within the quotes. A single quote may not occur between single quotes, even when preceded by a backslash.

Not to say they are always the right choice though.

[–] lagoon8622@sh.itjust.works 6 points 1 week ago

The shell doesn't expand or interpolate single-quoted strings, they are literals

[–] supersquirrel@sopuli.xyz 1 points 1 week ago* (last edited 1 week ago)

If you're contemplating doing something destructive, do a dry-run first.

@vk6flab@lemmy.radio is a WITCH I tell you! This is black magic!!