11 October 2006

Useful shell aliases

In a shell, an alias is a user defined command that will execute some other predefined, and usually longer, command. It's a tremendously useful command line feature that allows you take the longer commands that you use often and make them very short. I also use aliases to, in effect, redefine basic commands to always use the options that I prefer. For example, two commands I often use in FreeBSD to get a quick look at the network status of a box are "netstat -rn" to see the routing tables, and "netstat -an" to see the network connections. I might type these commands many times when there is a 'situation'. So, I've defined these aliases to give me some much shorter, time saving alternatives:

alias nsr='netstat -rn '
alias nsa='netstat -an | sed -n "1,/Active UNIX domain sockets/ p"'

These two lines are in the file "~/.bash_profile" and are executed for me whenever I login. The sed command that I'm piping the "netstat -an" command through just cuts off the domain sockets listing which, on a busy machine, is usually long enough to cause the network connections to be beyond a page/screen long. Then again, on a machine with a really large number of network connections, the output from "nsa" may still be too long for your terminal. No problem -- "alias" to the rescue again:

alias nsa='netstat -an | sed -n "1,/Active UNIX domain sockets/ p" | more'

I put a lot of importance on the modification time of a file. So, the basic ls command does nothing for me. I always want to see the modification times and I always(*) want to see the files in modification time order. Furthermore, if I copy a file, I want to preserve the modification time -- the content still hasn't changed yet. Since I pretty much always want these options, I will use the alias command to redefine these basic commands to suit my own tastes:

alias ls='ls -lt'
alias cp='cp -p'

Here are few more basic aliases that I've found to be very useful with short explanations for each:

#"change back" to the last directory you were in.
# Automatic shell variable, OLDPWD, is from bash.
alias cb='cd $OLDPWD'

#This one is good one to help standardize your command line across different OS's.
# I think it was "alias psa='ps -ef'" on Sun
#"process status all"
alias psa='ps auwx'

#"list directories", lists all of the subdirectories (names not contents) in the current directory
alias lsd='ls -d */'

#I quit after a few pings, because forever is a long time. :)
# (Also, notice 5 pings is more than a certain other OS's default 4. :D )
alias ping='ping -nc 5 '

# * -- did I say "always"? Once in a while I want to find a specific
# file name in very full directory and alphabetical listing is better.
#"list alphabetcial" (aliases will expand inside other aliases, hence the absolute path)
alias la='/bin/ls -l'

I've also written a second article on this subject, "More useful shell aliases." There we'll find that shell aliases plus grep equals a happy sysadmin -- and a decent cup of tea, to boot!

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05 October 2006

Java binaries for FreeBSD

You know, some of us will like to reminisce about the old days of getting Java on FreeBSD. You could't just type "make install" because a manual download was required. You had to go to a Sun website, create an account, dig around for the right SCSL source files, then check off on some license agreement, then go to another site for the FreeBSD patches, check off on something else. After all of this, you'd better have a good book ready because, even on a fast machine, compiling Java was going to take some serious time, like hours.

Yes, some will like to recall the days before things were so easy. We had to walk to school, in the snow, uphill, manually download source code, and then compile it on an abacus, by candle light! ... But, we sure as hell won't try to relive them. We'll go to the FreeBSD Foundation and download the licensed, compatibility tested binaries. The entire download/install process should take less time than it took you to read this post! Big kudos to the FreeBSD Foundation.