Comments on: Learning the Bash Shell

By: Greg Laden

Greg Laden — Sun, 24 Feb 2008 15:35:02 +0000

Citizen: Ha, “code” worked. I had thought it would not given prior experience…Looks pretty good, too.

By: Citizen Z

Citizen Z — Sun, 24 Feb 2008 13:19:03 +0000

Greg, for code snippets you can surround them with either the HTML <sample> or <code> tags. That should change the default font in most browsers automatically, and they're valid HTML tags.

By: peter

peter — Sun, 24 Feb 2008 05:01:25 +0000

#!/usr/bin/env bashsince bash may live elsewhere…

By: Greg Laden

Greg Laden — Sat, 23 Feb 2008 22:04:03 +0000

All excellent suggestions. I’ll address each of them in my next post on the topic.I hope to have a CSS style appropriate for code as well.One quick thing for now: The main syntax error in my code is the lack of spaces after the “[” and before th e “]}This is interesting. There needs to be a space before and after the [ because [ is a command in bash … it is not punctuation. The closing] on the other end is required (I think) in order to make the command structure excessively obscure. Kind of a joke, really.So test -e $1 && exit 0 is like [ -a $filename] because [ means ‘test’ in bash.test -e $1 and [ -a $filename] are the same kind of command because test = [ and they do the same thing because $1 is a parameter, and in my code, you would enter a filename. So if my program was named “isit” the one might enter on the command line:isit document.txtand if document.txt exists, then absolutely nothing happens (a standard *nix result). But the value returned would be 0, so my command could be used in another bash program like this:if isit document.txt …and if the document.txt file exists, the if statement gets a zero, which in bash means “yes” or “true.”Rpenner: It was very bad of me to not have the alternative (if the file does not exist) return a ‘1’ … which in bash means “no” or “false”Crap, I’ve said more than I want to…

By: rpenner

rpenner — Sat, 23 Feb 2008 15:48:45 +0000

I have to recommend that you switch to a monospaced font for code examples where spaces are important and you want people to know if your zero is a number. (Admittedly, I can't figure out how to do that when

,  and  don't work for me in Preview.)Also, -a might work for what is built into bash, but -e or -f might fit your intent better, especially if you port your script to a shell which relies on an external binary to implement these sorts of tests.And why does your code fall off the end without an exit for the alternative case? This would make sense if this was the preamble to a script whose job it was to create the file one time only and signal success in the event it made the file or if the file was already there.And if what is coded is your intent, what's wrong with:test -e $1 && exit 0There is something wrong with my example, but it is not the syntax. (It is the differnce between computer science (best way) and electrical engineering (least keystrokes to make it work this time).)

By: Jim Jim — Sat, 23 Feb 2008 14:56:40 +0000 For those stuck in a Windows world, cygwin allows you to use a BASH shell (and a lot of other things) within Windows. It's a valuable tool for those of us who need to run Windows, but need something more powerful than DOS (unless you really like DOS, of course). By: Tony P Tony P — Sat, 23 Feb 2008 13:53:22 +0000 #!/bin/bash