Simplify a BASH scripting design

Question

I have need to execute a command in a script an arbitrary number of times with associated arbitrary parameters.

I've decided the script will take its cue from a parameter file (parameter.txt) where lines are of the form:

label param1 param2

For each line in parameter.txt, I'll call the command with the specified parameters.

So far, my tinkering is moving along the lines of the following, but it's looking messy:

while read line; do 
    echo $line | sed -r 's/[^ ]+ ([^ ]+).+/\1/' && 
        echo $line | sed -r 's/[^ ]+ [^ ]+ ([^ ]+)/\1/'
done < parameter.txt

My command is of the form:

mycmd -a param1 -b param2 > label

Could I get some suggestions how I might simplify this?

I'm doing this for a small embedded system whose 'helper' commands are in short supply (xargs for example isn't available, and things like awk are hobbled busybox implementations), and I'm using version 2 (2.04g I think) of BASH.

John Kugelman · Accepted Answer · 2011-06-28 15:34:55Z

6

while read label param1 param2; do
    mycmd -a "$param1" -b "$param2" > "$label"
done < parameter.txt

answered Jun 28, 2011 at 15:34

John Kugelman

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2 Comments

Jamie Over a year ago

Love it. Full points for brevity and making me feel sheepish for not RFM'ing the read man page.

kamae Over a year ago

If you want to ignore after param3, use read label param1 param2 ignored instead.

Douglas Leeder · Accepted Answer · 2011-06-28 15:30:45Z

3

I'd suggest a function, as long as there aren't any embedded spaces.

function x()
{
    mycmd -a $2 -b $3 >$1
}

while read line; do x $line ; done <parameter.txt

answered Jun 28, 2011 at 15:30

Douglas Leeder

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1 Comment

Jamie Over a year ago

Nice. I hadn't thought of parameterizing the line with a function call, will add that to my bag of tricks. +1

Aaron Digulla · Accepted Answer · 2011-06-28 15:32:10Z

1

Try this:

while read line ; do
    set -- $line
    dest="$1"
    shift

    mycmd "$@" > "$dest"
done < parameter.txt

should work. If the parameters in the file have spaces, you will have to quote them properly.

I suggest to add the -a, -b to the file parameter.txt because generating them on the fly is probably brittle.

If you don't like this solution, then I suggest to create a new script from this one which contains the actual commands. That way, you can easily debug any problems.

When the script looks okay, you can source it with source ./generated.sh (yes, you have to specify the path).

answered Jun 28, 2011 at 15:32

Aaron Digulla

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