BASH - Read in config file with multiple instances of the same "variable"

Question

I'm trying to read a config file, and then place the "section" of configs into an array in a bash script, and then run a command off that, and then reitterate through the configs again, and continue to do this until the end of the config file.

Here's a sample config file:

PORT="5000"
USER="nobody"
PATH="1"
OPTIONS=""

PORT="5001"
USER="nobody"
PATH="1"
OPTIONS=""

PORT="5002"
USER="nobody"
PATH="1"
OPTIONS=""

I want the bash script to read in the first "section", bring it into the script, and run the following:
scriptname -p $PORT -u $USER -P $PATH -o $OPTIONS

HOWEVER, I want it to, based on how many "sections" there are in the config file, to take each iteration of a "section", and run the command with its corresponding configuration settings and apply it to the final command. So if it were to read in the config file from above, the output would be:

scriptname -p $PORT -u $USER -P $PATH -o $OPTIONS
scriptname -p $PORT -u $USER -P $PATH -o $OPTIONS
scriptname -p $PORT -u $USER -P $PATH -o $OPTIONS

Which in turn would look like:

scriptname -p 5000 -u nobody -P 1 -o ""
scriptname -p 5001 -u nobody -P 1 -o ""
scriptname -p 5002 -u nobody -P 1 -o ""

Thanks in advance.

Since this looks like a mini-language of your own design, do yourself a favor and have something other than whitespace demarcate the logical blocks. — msw
– msw, Commented Aug 4, 2010 at 22:40
Right now, the whitespace blocks will have to do. This is basically a fix for another application - it's temporary, but a quick fix needs to be in place. I'm having to implement this into an init script. The config file needs to be simple. — drewrockshard
– drewrockshard, Commented Aug 4, 2010 at 23:16

John Kugelman · Accepted Answer · 2010-08-06 22:25:58Z

3

#!/bin/bash

if [[ $# -ne 1 ]]; then
    echo "Usage: $0 script.cfg" >&2
    exit 1
fi

function runscript() {
    scriptname -p $PORT -u $USER -P $PATH -o $OPTIONS
}

while read LINE; do
    if [[ -n $LINE ]]; then
        declare "$LINE"
    else
        runscript
    fi
done < "$1"

runscript

If you want to run the scripts in the background simultaneously, try this:

function runscript() {
    nohup scriptname -p $PORT -u $USER -P $PATH -o $OPTIONS &> /dev/null &
}

The & at the end makes them run in the background and nohup ensures they're not killed when the shell exits. The net effect is to turn the scripts into daemons so they'll run continuously in the background regardless of what happens to the parent script.

edited Aug 6, 2010 at 22:25

answered Aug 4, 2010 at 22:34

John Kugelman

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4 Comments

drewrockshard Over a year ago

I'm actually trying to implement this into a startup script. It works, however, it only runs one instance of the scriptname stanza. I changed the while loop to read in from a config file. Like I said, my mods work, BUT it only starts one program, not the other ones.

John Kugelman Over a year ago

Do you mean it only invokes the script once and then quits, or it invokes the script and blocks because the script doesn't exit? If it's the latter I've edited my answer to accommodate. If it's the former I'll need more info on what's not working--the script worked when I tested it with your sample config file.

Dennis Williamson Over a year ago

You should change eval to declare. There are security risks with eval that declare avoids (even though in this case the input file is presumably safe, it's a good habit to change). You'll need to change the logic a bit. Something like [[ -z $LINE ]] && runscript || declare "$LINE"

Hasturkun Over a year ago

You don't need nohup if you're using disown

ghostdog74 · Accepted Answer · 2010-08-05 00:15:46Z

2

#!/bin/bash

awk 'BEGIN{ FS="\n";RS=""}
{
  for(i=1;i<=NF;i++){
   gsub(/.[^=]*=|\042/,"",$i)
  }
  print "scriptname -p "$1" -u "$2" -P "$3" -o "$4
}' file | bash

answered Aug 5, 2010 at 0:15

ghostdog74

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2 Comments

Gilles 'SO- stop being evil' Over a year ago

That's a nice solution. In fact, you could replace print by system and get rid of the | bash.

ghostdog74 Over a year ago

yes.that's another way provided its not a lot. If its a lot, piping to xargs and bash would be better than calling system().

Kaleb Pederson · Accepted Answer · 2010-08-04 22:35:35Z

0

Assuming there is only one empty line between sections:

cat <yourfile> | while read ; do
    if [ -z "$REPLY" ] ; then
        scriptname -p $PORT -u $USER -P $PATH -o "$OPTIONS" 
    else
        eval "$REPLY" # NOTE: eval is evil
    fi
done

answered Aug 4, 2010 at 22:35

Kaleb Pederson

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2 Comments

Dennis Williamson Over a year ago

That's why you should change eval to declare - it works and it's safer. Oh, and cat is unnecessary. Use done < filename. If nothing else, it saves a call to an external executable.

Kaleb Pederson Over a year ago

Thanks for the note on declare, I'll have to remember that. RE: cat -- old habits die hard :).

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