How to get specific data from block of data based on condition - bash

Question

I have a file like this:
[group]
enable = 0
name = green
test = more
[group]
name = blue
test = home
[group]
value = 48
name = orange
test = out
There may be one ore more space/tabs between label and = and value.
Number of lines may wary in every block.
I like to have the name, only if this is not true enable = 0
So output should be:
blue
orange
Here is what I have managed to create:
awk -v RS="group" '!/enable = 0/ {sub(/.*name[[:blank:]]+=[[:blank:]]+/,x);print $1}'
blue
orange
There are several fault with this:
I am not able to set RS to [group], both this fails RS="[group]" and RS="\[group\]". This will then fail if name or other labels contains group.
I do prefer not to use RS with multiple characters, since this is gnu awk only.
Anyone have other suggestion? sed or awk and not use a long chain of commands.

Answer 1

If you know that groups are always separated by empty lines, set RS to the empty string:
$ awk -v RS="" '!/enable = 0/ {sub(/.*name[[:blank:]]+=[[:blank:]]+/,x);print $1}'
blue
orange
#devnull explained in his answer that GNU awk also accepts regular expressions in RS, so you could only split at [group] if it is on its own line:
gawk -v RS='(^|\n)[[]group]($|\n)' '!/enable = 0/ {sub(/.*name[[:blank:]]+=[[:blank:]]+/,x);print $1}'
This makes sure we're not splitting at evil names like
[group]
enable = 0
name = [group]
name = evil
test = more

Answer 2

Your problem seems to be:
I am not able to set RS to [group], both this fails RS="[group]" and
RS="\[group\]".
Saying:
RS="[[]group[]]"
should yield the desired result.

Answer 3

In these situations where there's clearly name = value statements within a record, I like to first populate an array with those mappings, e.g.:
map["<name>"] = <value>
and then just use the names to reference the values I want. In this case:
$ awk -v RS= -F'\n' '
{
delete map
for (i=1;i<=NF;i++) {
split($i,tmp,/ *= */)
map[tmp[1]] = tmp[2]
}
}
map["enable"] !~ /^0$/ {
print map["name"]
}
' file
blue
orange
If your version of awk doesn't support deleting a whole array then change delete map to split("",map).
Compared to using REs and/or sub()s., etc., it makes the solution much more robust and extensible in case you want to compare and/or print the values of other fields in future.

Answer 4

Since you have line-separated records, you should consider putting awk in paragraph mode. If you must test for the [group] identifier, simply add code to handle that. Here's some example code that should fulfill your requirements. Run like:
awk -f script.awk file.txt
Contents of script.awk:
BEGIN {
RS=""
}
{
for (i=2; i<=NF; i+=3) {
if ($i == "enable" && $(i+2) == 0) {
f = 1
}
if ($i == "name") {
r = $(i+2)
}
}
}
!(f) && r {
print r
}
{
f = 0
r = ""
}
Results:
blue
orange

Answer 5

This might work for you (GNU sed):
sed -n '/\[group\]/{:a;$!{N;/\n$/!ba};/enable\s*=\s*0/!s/.*name\s*=\s*\(\S\+\).*/\1/p;d}' file
Read the [group] block into the pattern space then substitute out the colour if the enable variable is not set to 0.
sed -n '...' set sed to run in silent mode, no ouput unless specified i.e. a p or P command
/\[group\]/{...} when we have a line which contains [group] do what is found inside the curly braces.
:a;$!{N;/\n$/!ba} to do a loop we need a place to loop to, :a is the place to loop to. $ is the end of file address and $! means not the end of file, so $!{...} means do what is found inside the curly braces when it is not the end of file. N means append a newline and the next line to the current line and /\n$/ba when we have a line that ends with an empty line branch (b) to a. So this collects all lines from a line that contains `[group] to an empty line (or end of file).
/enable\s*=\s*0/!s/.*name\s*=\s*\(\S\+\).*/\1/p if the lines collected contain enable = 0 then do not substitute out the colour. Or to put it another way, if the lines collected so far do not contain enable = 0 do substitute out the colour.

Answer 6

If you don't want to use the record separator, you could use a dummy variable like this:
#!/usr/bin/awk -f
function endgroup() {
if (e == 1) {
print n
}
}
$1 == "name" {
n = $3
}
$1 == "enable" && $3 == 0 {
e = 0;
}
$0 == "[group]" {
endgroup();
e = 1;
}
END {
endgroup();
}

Answer 7

You could actually use Bash for this.
while read line; do
if [[ $line == "enable = 0" ]]; then
n=1
else
n=0
fi
if [ $n -eq 0 ] && [[ $line =~ name[[:space:]]+=[[:space:]]([a-z]+) ]]; then
echo ${BASH_REMATCH[1]}
fi
done < file
This will only work however if enable = 0 is always only one line above the line with name.