Hey everyone! I'm trying to figure out why using `*` seems to have priority over the `-B` option in the `ls` command. I was looking for files that start with the letter 'L' but want to avoid any backup files. I have two ways to do this: one is using the command `l L*`, which is an alias for `ls -B`, and the other is using `ls -B L*`. When I run both commands, I still see both 'Lubuntu' and 'Lubuntu~' listed. I thought the `-B` option was supposed to filter out backup files, but it's like `*` takes precedence. Can someone clarify this for me? Thanks!
5 Answers
It sounds like you're running into a common misunderstanding with how the bash shell processes wildcards. When you use `L*`, bash expands that to match any file that starts with 'L', including backups like 'Lubuntu~'. By the time `ls` runs, it sees those names directly and doesn't apply the `-B` option to them because they're explicitly listed. If you want to use `-B` effectively, you should run `ls -B` without specifying a filename or wildcard.
Exactly! The `-B` option only applies to 'implied' files, which means files that are in the directory but not specified as an argument. Since 'Lubuntu' and 'Lubuntu~' are directly passed in as arguments when you use `L*`, they bypass the `-B` filter. If you run `ls -B` without any files, then it will correctly filter out the backups if they aren't explicitly mentioned.
Definitely! Just remember that `*` is processed by bash during the command expansion, so it takes precedence and gives explicit filenames to `ls`.
One more thing to consider is that using `--ignore-backups` or `--ignore=` would affect this too, but again, those are for files that aren't explicitly mentioned in the command. So in your case, you must manage how you're calling `ls` and what arguments you pass to it.
Just to add on, if you want to specifically list files that start with 'L' but exclude backups, you can use `ls -B | grep "^L"` to filter the output after getting all files. That way, you'll have the backup files excluded.
If you want to learn more, check the documentation for bash and `ls`. It can get quite intricate with how arguments and wildcards interact!
Good point! It’s all about when the filtering happens. Wildcards are expanded before the command runs, so `-B` won't filter anything that's already been explicitly listed.