This may be a dumb question, but googling is not giving me an answer. I'm trying to figure out how to refer to an input file in my code.

Lets say i run a script in bash:

"sh shellscript.sh inputfile"
(Inputfile will be variable...whatever file i run the script on)

I wanted to make variables like "DIR=dirname inputfile" and "BASE = basename inputfile" so that I can use those to make subsequent files based off of the basename and put them in directories based on the dirname rather than having to cd to the directory to run the script and keep the output files in that folder. The problem is that I don't know how to refer to the inputfile to initially set these variables.

Also, if I set these variables at the beginning of the whole shell script, they will stay throughout for all of the other commands I am performing, right?

Positional parameters is the term you need to look for when searching. They should be documented in your shell's manual page. They are shell variables (aka parameters) of the form $1, $2 ... $N, where N is the number of arguments with which the script was called. You'll also want to learn about the related special variables $* and $@.

Regards,
Alister

Thanks! Finally got the right search term. After a little more searching, fyi for posterity, i set the variables with:

DIR=`dirname $1`
INPUT=`basename $1`

I was having problems before too because I didn't realize that there could be no spaces when setting variables!
Works now, thanks again.

EDIT: Not working... sort of pissing me off. I did this the first time, and it returned the dirname and basename of the file the script was running on with $1, but now it won't anymore. dirname is empty and it just returns "usage:dirname path"

EDIT: And it works again...I realized that getting the dirname from $1 or $0 the way I am doing it gets problems if any of the folders in the path have spaces in them because i assume that it takes the space for a new "field"... Might be using improper terminology, but $1 might become $2 for example. My solution was to remove spaces from folder names... Anyone know how to do this otherwise so that there won't be a problem?

As a wild guess, I'd say that the times it didn't work, you invoked your shell script with no operands.

In other words, yourscript filename should work, but yourscript will fail with errors similar to what you described above.

I checked, I did use operands those times. Repeated mistakes when there are spaces in directory paths reveal that to be the problem.

OK. So, I assume you've figured out this can be fixed by using appropriate quoting. In this case:

DIR=`dirname "$1"`
INPUT=`basename "$1"`

DIR=$(dirname "$1")
INPUT=$(basenamae "$1")