[SOLVED] Parsing simple config files in pure bash

Question

Hi everyone,
I'd like to implement a bash function to parse a simple config file for a script I've wrote. The conifg file contains different sections for different scenarios. Here's an example how it should look like:
# configuration file
# global settings
global {
DATE_PREFIX="-I"
SSHFS_OPTS="-C"
EXT_FULL="full"
EXT_DIFF="diff"
EXT_CATALOGUE="catalogue"
DAR_OPTS="-v -m 256 -y -s 600M -D"
DAR_NOCOMPR="-Z '*.gz' -Z '*.bz2' -Z '*.zip' -Z '*.png'"
# system settings
system {
DAR_OPTS="-v -m 256 -y -s 200M -D"
It contains some settings which are global for the whole script and special settings groups which can be used to overwrite global settings.
The function to parse this config file looks as follows:
#!/bin/sh
CONFIG="/home/chi/.daruprc"
function readconf() {
match=0
while read line; do
# skip comments
[[ ${line:0:1} == "#" ]] && continue
# still no match? lets check again
if [ $match == 0 ]; then
# do we have an open tag ?
if [[ ${line:$((${#line}-1))} == "{" ]]; then
# strip "{"
group=${line:0:$((${#line}-1))}
# do we have a match ?
if [[ ${group} -eq $1 ]]; then
match=1
continue
fi
continue
fi
# found close tag but still no match - continue
elif [[ ${line:0} == "}" && $match == 0 ]]; then
continue
# found close tag after config was read - exit loop
elif [[ ${line:0} == "}" && $match == 1 ]]; then
break
# got a config line return it
else
echo $line
fi
done < "$CONFIG"
for line in $(readconf "system"); do
echo $line
done
As you can see I try to just echo the lines at the moment. And here's the problem: It seems I have some " escape issues, if I run it I get the following output:
./parseconfig.sh
DATE_PREFIX="-I"
SSHFS_OPTS="-C"
EXT_FULL="full"
EXT_DIFF="diff"
EXT_CATALOGUE="catalogue"
DAR_OPTS="-v
-m
256
-y
-s
600M
-D"
DAR_NOCOMPR="-Z
'*.gz'
-Z
'*.bz2'
-Z
'*.zip'
-Z
'*.png'"
As you can see there are way to much newlines - which leads to problems when I try to use "eval" to initialize the variables.
I am sure I am missing something simple here, however I am looking for a solution for a few days now - maybe one of the bash gurus on this board can enlighten me ;-).
Thanks in advance
PS.: I am trying to do this in pure bash because the script also needs to run on embedded machines with very low memory like my router on which I don't have sed or awk or the like. I also know that I could for example just use different config files to circumvent the whole parsing - but I am just curious if this could work the way I like ;-).
Last edited by chimeric (2007-11-04 23:20:58)

Answer 1

chimeric wrote:
Hi MrWeatherbee,
well yes, but I want to assign (eval) these lines to get variables out of them. Since the while loop is trapped in its' own subshell I need to return the lines into the parent one to be able to make these variables "visible" in the script itself.
Right. But I was trying to show you that the way you were going about it wouldn't work at a very fundamental level.
Without changing too much code just for a quick and dirty demo,
change:
# got a config line return it
else
echo $line
fi
done < "$CONFIG"
# got a config line return it
else
line_array=( "${line_array[@]}" "$line" )
fi
done < "$CONFIG"
numarrayelements=${#line_array[@]}
and then in the main program code, do this:
readconf "system"
for index in $( seq $numarrayelements ); do
line=${line_array[(($index-1))]}
echo $line
done
Using an array to collect the good lines from the function allows you to reuse them later for whatever purpose. Although other ways exist, you certainly don't want to do what you originally did.
Edit:
I posted the code with an incorrectly referenced variable and had to fix it.
Last edited by MrWeatherbee (2007-11-04 22:46:34)