John Stanfield dot com

I was looking for a quick and dirty way to SSH into a handful of hosts. I SSH into these hosts all day long, and I was looking for a way to skip the password prompt (I’m way too much into efficiency — every second counts!). I wasn’t interested in learning how to set up the public/private key authentication. I just wanted to automate the login so all I would need to type is goto host. Obviously this is less than secure, but I’m not overly concerned with security at my workstation.

Here’s what I came up with:

1) a file named goto.passwd
– which contains hostnames, usernames, and passwords (e.g. myhost myuser mypassword)
2) a script named goto
– which accepts one parameter (e.g. goto myhost)
– parses the goto.passwd file looking for that host
– and then passes that info to
3) a script borrowed from here
– and slightly modified.

Here is an example (the command is simply goto myhost and I’m instantly in.):

Here are the scripts (you can also download them as a zip or tar):

goto.passwd

myhost root password
myotherhost root passwordforroot
anotherhost root password12345

goto

#!/bin/bash
host=$1
user=`cat goto.passwd | grep -e ^$host | awk '{print $2}'`
pass=`cat goto.passwd | grep -e ^$host | awk '{print $3}'`
goto.expect $user $pass $host

goto.expect

omitted. see zip or tar file below.

goto.tar
goto.zip

Someone came to me today and asked if I could track down a 403 error that was handed to a user the morning of 4/13/2010. The web server log file is 465 megs. Gulp. sed and grep to the rescue!

Just pick a random number (representing a wild guess at where, in the log file, your starting point may be) and use sed -n 2000p where 2000 is your random number. My original guess was way off. The time period in question ended up spanning lines 500,000 to 680,000 in the server log. Great, just read 180,000 lines, right? WRONG! Use grep. Here’s the final string of commands I used.

# just to locate the correct line...
sed -n 2000p site-access_log
sed -n 12000p site-access_log
sed -n 100000p site-access_log
sed -n 300000p site-access_log
sed -n 500000p site-access_log
sed -n 680000p site-access_log

# now to search that time period for a 403 error
sed -n 500000,685000p site-access_log | grep ' 403'

Not perfect, but good enough to get the job done. sed whittled the 465 meg file down to 180,000 lines, and grep whittled that down to 50 or so lines, some of which were relevant, others not.

I love simple problems, such as fill a drop-down with a range of feet and inches.

One way to do it is to hand-code a <select> element and fill it with hand-coded <option> elements, but what’s the fun in that?

It’s more fun to iterate over an array (range) of integers representing inches, and do the math to convert those inches to feet and inches. To get feet, use the floor function, which truncates all decimal places without rounding. To get inches, use the modulus operator (the % operator) which returns the remainder. 36 is 3′0″ and 74 is 6′2″.

The math is the same but (as John Madden would say, if he were a programmer) the syntax varies by language… Here’s how you do it in Ruby:

<%= select :person,
       :height,
       (36..95).collect{|i|["#{(i/12).floor}' #{i%12}\"",i]},
       {:selected=>@person.height} %>

And here’s what you end up with:

And unformatted:

So, I just checked in some files and I realized “doh! I didn’t check to see if there’s any debug trash in there!” My debug trash is fairly easy to detect: I only use raise or puts in Ruby and alert in JavaScript for basic “hello world” type things when debugging some particular issue.

Trouble is, sometimes I forget to remove that trash code before checking it in. To prevent big problems, I refrain from using the Ruby raise command and instead use puts which is fairly harmless. Anyway, I wrote a script to 1) ask SVN for the list of files modified by my checkin and 2) use awk to figure out the file names and, within a loop, 3) use cat to pass the contents of each file to 4) grep / egrep to look for alert, raise, and/or puts statements within the files. So now I have an example of a handful of common Linux commands that I can post here for future reference.

for l in `svn log -r 298 -v | egrep M | awk '{print $2}'`;
do
echo ${l};
cat .${l} |
egrep 'alert|puts|raise';
done

Which spat out:

/app/models/some_model.rb
/app/models/some_other_model.rb
/app/models/foo_model.rb
/app/controllers/home_controller.rb
    puts "hello world"
/app/controllers/foo_controller.rb
    #puts "hello world"
/app/controllers/other_controller.rb
    puts "hello world" unless some_condition

And I found three instances of debug trash… One commented out, one from a previous check-in, and one that I need to remove!

And on one line, without formatting:

This is something that really pisses me off: FireFox 3 makes downloaded files read-only because they’re saved in /tmp, and OpenOffice doesn’t let you manipulate a read-only file. Even for something stupid and simple, like changing page margins, you have to click the pencil icon in the toolbar, click OK to an error message, and click Yes to something else. FF says “it’s supposed to be read-only, have OO fix it” and OO says “it’s read-only, tell FF to make it not read-only” and lowly-user daresay “M$ Turd handles this gracefully” and “Hey, FF, if you had made this a user-configurable option in FF3 instead of doing a global search & replace, this wouldn’t be an issue!”

Well to hell with it. This script fixes the problem by watching /tmp for files ending in doc,csv,xls,odf (and some others) and makes them writable by using the inotifywait command, which is part of the inotify-tools package. I use openSUSE so it was easy to find in the Install Software applet.

I was going to make an init.d script out of it, but I am busy… It’s just running in a Konsole on Desktop 4 along with all the other out-of-the-way stuff.

#!/bin/bash

# author John Stanfield
# makes files in /tmp/ writable upon creation
# this is a workaround for the religious war between OpenOffice and Mozilla regarding read-only files
# it's intended for users who want to
#  1) download a file
#  2) make a small edit (e.g. page margin, white space, etc)
#  3) read it, print it, email it, etc
#  4) IMPORTANT!
#     a) not be upset if the file is, accidentally or otherwise, deleted in the future
#     or
#     b) save the file elsewhere

inotifywait -m -e create --format %w%f /tmp/ | while read line
do
  if (echo found file... ${line} | egrep "\.od[t|s|p|g|f]$|\.csv$|\.doc$|\.rtf$|\.xls$|\.ppt$"); then
    chmod +w "${line}"
    echo `date` made ${line} writable
  fi
done

#!/bin/bash

# author John Stanfield
# makes files in /tmp/ writable upon creation
# this is a workaround for the religious war between OpenOffice and Mozilla regarding read-only files
# it's intended for users who want to
#  1) download a file
#  2) make a small edit (e.g. page margin, white space, etc)
#  3) read it, print it, email it, etc
#  4) IMPORTANT!
#     a) not be upset if the file is, accidentally or otherwise, deleted in the future
#     or
#     b) save the file elsewhere

inotifywait -m -e create --format %w%f /tmp/ | while read line
do
  if (echo found file... ${line} | egrep "\.od[t|s|p|g|f]$|\.csv$|\.doc$|\.rtf$|\.xls$|\.ppt$"); then
    chmod +w "${line}"
    echo `date` made ${line} writable
  fi
done

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