Category: Coding

A new blog that I installed using the TwentyFifteen theme has annoying hyphenation on the posts. I found an easy fix online. Open the style.css file and insert this at the end.

.entry-content,
.entry-summary,
.page-content,
.nav-links,
.comment-content,
.widget
 {
   -webkit-hyphens: none;
   -moz-hyphens:    none;
   -ms-hyphens:     none;
   hyphens:         none;
}

I don’t do much shell scripting, but every once in a while I use it to automate things. I was playing around with bash today and thought this might interest others.

Define an array variable
$ servers=(server purple yellow dan);
$ echo $servers
server

Redefine it.
$ servers=(firstserver server purple yellow dan);
$ echo $servers
firstserver

That’s not what I want. So how do we access the values? Let’s try a for loop.
$ for name in $servers; do echo $name; done;
$ echo $servers
firstserver

Well that didn’t do it. Let’s try to access the second value with array notation.
$ for name in $servers; do echo $servers[1]; done;
firstserver[1]

If you look carefully at this you’ll notice that what is happening is that you are concatenating the return value from $server with [1]. Try it again with this line.

$ for name in $servers; do echo $servers[a]; done;
firstserver[a]

And again.
$ for name in $servers; do echo $servers.a; done;
firstserver.a

As long as you use a character that is not a valid part of a variable name, you get concatenation.
e.g. don’t use an alphanumeric.
$ for name in $servers; do echo $serversabc; done;

There is no variable called serverabc, so you get a blank line.

It turns out that bash has weird syntax for working with variables.
$ echo ${servers[2]}
purple

Add another value.
$ servers[5]=finalvalue
$ echo ${servers[5]}
finalvalue

So how about we separate out the loop variable like this?
$ for name in $servers; do echo $servers${name}; done;
firstserverfirstserver

Well, we’re getting warmer.
$ for name in $servers; do echo $name; done;
firstserver

This is getting frustrating. Let’s back up and try just listing a bunch of stuff in a list.
$ for name in firstserver server purple yellow dan finalvalue; do echo $name; done;
firstserver
server
purple
yellow
dan
finalvalue

So we can make a for loop iterate through items, but the normal way of accessing elements of an array doesn’t work in bash. It turns out that you need special syntax.

$ echo ${servers[@]}
firstserver server purple yellow finalvalue finalvalue

And to loop through everything like we wanted to do at the start.
$ for name in ${servers[@]}; do echo $name; done;
firstserver
server
purple
yellow
dan
final value

That wasn’t so hard was it?

After the 100% full hard disk problem I couldn’t get MySQL to restart. I looked at the error logs and found these lines.

151010 16:51:18 [ERROR] /usr/sbin/mysqld: Table './SS_connellsville/alerts' is marked as crashed and should be repaired
151010 16:51:18 [Warning] Checking table:   './SS_connellsville/alerts'
151010 16:51:56 [ERROR] /usr/sbin/mysqld: Table './SS_greensburg/values_RSSI_3' is marked as crashed and should be repaired
151010 16:51:56 [Warning] Checking table:   './SS_greensburg/values_RSSI_3'
151010 16:51:58 [ERROR] /usr/sbin/mysqld: Table './master/node_groups' is marked as crashed and should be repaired
151010 16:51:58 [Warning] Checking table:   './master/node_groups'

A stackoverflow post recommended using mysqlcheck. It must be used when the mysqld server is running. I couldn’t see how to set it to just repair the databases that were causing problems, but I figured that it wouldn’t hurt to run it on all of them. I was a bit concerned that it would run into problems when the cron jobs ran, but I set it running anyway. It changed the record count on all of the databases and ran for many hours. At least six, but I stopped monitoring and let it run overnight. I stopped MySQL and did a restart and it started without errors.

mysqlcheck --repair --use-frm --all-databases

Often I need to mess with the content of arrays. They often look like this.

“99”, ”

And I’ll want to delete the contents of one section.

^"([0-9]*)"(,"")(,"[a-zA-Z0-9 ,-/'&#ñéá]*")
"\1"\3\2

This says, start at the beginning of each line ^, look for double quotes, then a number—repeated as many times as you want, then another double quote,

Look for any letter, number, and a bunch of special characters that don’t include double quotes “.

([a-zA-Z0-9 ,-/’&#ñéá]*)