Merge two lines into one within a configuration file - perl

Question

I have several AIX systems with a configuration file, let's call it /etc/bar/config. The file may or may not have a line declaring values for foo. An example would be:
foo = A_1,GROUP_1,USER_1,USER_2,USER_3
The foo line may or may not be the same on all systems. Different systems may have different values and different a different number of values. My task is to add "bare minimum" values in the config file on all systems. The bare minimum line will look like this.
foo = A_1,USER_1,SYS_1,SYS_2
If the line does not exist, I must create it. If the line does exist, I must merge the two lines. Using my examples, the result would be this. The order of the values does not matter.
foo = A_1,GROUP_1,USER_1,USER_3,USER_2,SYS_1,SYS_2
Obviously I want a script to do my work. I have the standard sh, ksh, awk, sed, grep, perl, cut, etc. Since this is AIX, I do not have access to the GNU versions of these utilities.
Originally, I had a script with these commands to replace the entire foo line.
cp /etc/bar/config /etc/bar/config.$$
sed "s/foo = .*/foo = A_1,USER_1,SYS_1,SYS_2/" /etc/bar/config.$$ > /etc/bar/config
But this simply replaces the line. It does take into consideration any pre-existing configuration, including a line that's missing. And I'm doing other configuration modifications in the script, such as adding completely unique lines to other files and restarting a process, so I'd perfer this be some type of shell-based code snippet I can add to my change script. I am open to other options, especially if the solution is simpler.

Answer 1

Some dirty bash/sed:
#!/usr/bin/bash
input_file="some_filename"
v=$(grep -n '^foo *=' "$input_file")
lineno=$(cut -d: -f1 <<< "${v}0:")
base="A_1,USER_1,SYS_1,SYS_2,"
if [[ "$lineno" == 0 ]]; then
echo "foo = A_1,USER_1,SYS_1,SYS_2" >> "$input_file"
else
all=$(sed -n ${lineno}'s/^foo *= */'"$base"'/p' "$input_file" | \
tr ',' '\n' | sort | uniq | tr '\n' ',' | \
sed -e 's/^/foo = /' -e 's/, *$//' -e 's/ */ /g' <<< "$all")
sed -i "${lineno}"'s/.*/'"$all"'/' "$input_file"
fi

Answer 2

Untested bash, etc.
config=/etc/bar/config
default=A_1,USER_1,SYS_1,SYS_2
pattern='^foo[[:blank:]]*=[[:blank:]]*' # shared with grep and sed
if current=$( grep "$pattern" "$config" | sed "s/$pattern//" )
then
new=$( echo "$current,$default" | tr ',' '\n' | sort | uniq | paste -sd, )
sed "s/$pattern.*/foo = $new/" "$config" > "$config.$$.tmp" &&
mv "$config.$$.tmp" "$config"
else
echo "foo = $default" >> "$config"
fi
A vanilla perl solution:
perl -i -lpe '
BEGIN {%foo = map {$_ => 1} qw/A_1 USER_1 SYS_1 SYS_2/}
if (s/^foo\s*=\s*//) {
$found=1;
$foo{$_}=1 for split /,/;
$_ = "foo = " . join(",", keys %foo);
}
END {print "foo = " . join(",", keys %foo) unless $found}
' /etc/bar/config

Answer 3

This Perl code will do as you ask. It expects the path to the file to be modified as a parameter on the command line.
Note that it reads the entire input file into the array #config and then overwrites the same file with the modified data.
It works by building a hash %values from a combination of the items already present in the foo = line and the list of defaults items in #defaults. The combination is sorted in alphabetical order and joined eith a comma
use strict;
use warnings;
my #defaults = qw/ A_1 USER_1 SYS_1 SYS_2 /;
my ($file) = #ARGV;
my #config = <>;
open my $out_fh, '>', $file or die $!;
select $out_fh;
for ( #config ) {
if ( my ($pfx, $vals) = /^(foo \s* = \s* ) (.+) /x ) {
my %values;
++$values{$_} for $vals =~ /[^,\s]+/g;
++$values{$_} for #defaults;
print $pfx, join(',', sort keys %values), "\n";
}
else {
print;
}
}
close $out_fh;
output
foo = A_1,GROUP_1,SYS_1,SYS_2,USER_1,USER_2,USER_3

Answer 4

Since you didn't provide sample input and expected output I couldn't test this but this is the right approach:
awk '
/foo = / { old = ","$3; next }
{ print }
END {
split("A_1,USER_1,SYS_1,SYS_2"old,all,/,/)
for (i in all)
if (!seen[all[i]]++)
new = (new ? new "," : "") all[i]
print "foo =", new
}
' /etc/bar/config > tmp && mv tmp /etc/bar/config