Entries this day: bash-one-liner oops-and-whew

bash one liner

08:32 Tuesday 25 April 2017 JST

I sent this to Fred yesterday:

I often type `gits` to get the status of git.

There is one directory on my filesystem that has a filename
starting with 0x0x which I must not commit to git, but I need to
see each time I get git status.

I wrote this

    alias gits='git status; if [[ -f 0x0x* ]]; then echo; ls -1 0x0x*; fi'

And it works to *not* complain if there is no 0x0x* file, but does
not show the file if it is present.

The problem is prolly small; can you fix this with just an alias?

Fred sorted it out last night. I replied inline:

alias gits='git status; if test -n "$(find . -maxdepth 1 -name 0x0x\*

-print -quit)"; then echo; ls -1 0x0x*; fi'

Sweet! It works well.

Escape the * the first time, but not the second time.

because the first one is in the $() ?

A couple gotchas that were emerging with your solution is that if

there is more than one match, the -f won't work. Maybe right now

you never have that, but let's fix it while we're here.

Definitely going to be more than one, so thank you for solving it! In fact, if the ls at the end could ignore files ending with ~, that would be great.

We can set 'shopt -s nullglob' which "allows patterns which match no

files (see Pathname Expansion above) to expand to a null string,

rather than themselves." But that's a bash-wide thing that might

bleed into your regular commands, so that's too risky.

yeah that sounds spooky.

I thought of writing it as a command, instead of an alias, where we

can take the time to do a lot of checking and shit, instead of being

short and sweet. Then I tried some other dumb ideas that I've

already forgotten now, and finally decided to hit stackoverflow,

with what appeared to be the main issue: we need only to know if the

glob matches, not what the match is, or how many there are. So I

googled "bash if glob matches"

There are a few good solutions, and a good explanation of why each

is useful here:

https://stackoverflow.com/questions/2937407/test-whether-a-glob-has-any-matches-in-bash

The one you want is probably

if test -n "$(find . -maxdepth 1 -name 'glob*' -print -quit)"

then

echo found

else

echo not found

fi

for portability, and familiarity with tools you already know.

Yay for tools I already know!

To put that solution in an alias, the quoting is awkward. The glob

is already nested inside ", ', and $(. The alias command wants

another nesting, and I'm out of quotes. So I removed the quotes

around the glob and escaped it instead. That worked. (Escaping the

quotes didn't for some reason.)

Write a new RFC to allow 「 」as quotes in bash!

So, your solution is as at the top.

Yahoooo, as is my thanks! Thanks for putting it at the top, cause I gotta get back to work!

oops and whew

12:53 Tuesday 25 April 2017 JST

I left the AB DB backup process in testing mode (backup every hour, do not clean up the files) and it killed the disk this morning and locked up the server.

Thankfully, I was able to request support from AWS. They called me immediately and helped me dismount the flooded disk, remount it at /mnt on a different server where I was able to clean up the disk, then remount it on AB server and get the server running again.

As a result of some part of that process, the mysql server got a sad and corrupted a DB table. So then the mysql server could not write to that table. Thank goodness AB noticed the problem quickly and I was able to rebuild the table to get it working again.

Now I just need to copy 14 records from the mysql log to the table in question, and everything will be as I hoped it would be this morning at 9am when I hoped to start working on a different project.