[SOLVED] print lines that don't match array elements

Issue

I have an array

arr=( 'error one' 'error two' 'error three' )

and a file I want to find errors in

a.txt

with contents (example).

error one
error two
error three
error four
error five
error six
error seven
eight
nine
ten

When I run my script I want to ignore all errors I have already found (the errors in the array) and find new ones.

So far I have this

arr=( 'error one' 'error two' 'error three' )
grep -v 'error one\|error two\|error three' a.txt | grep error

which returns this (correct).

error four
error five
error six
error seven

The contents of the array will change over time though, based on more errors I find, or errors I stop finding, and I would prefer to instead reference the array as a whole rather than list each item.

So far I have something like this.

arr=( 'error one' 'error two' 'error three' )
function join_by { local d=$1; shift; echo -n "$1"; shift; printf "%s" "${@/#/$d}"; }
list=$(join_by "\|" "${arr[@]}")
echo ${list}
grep -v ${list} a.txt | grep error

Of course this doesn't work, but I don't know how to proceed from here, or whether to change the method entirely.

Any help would be appreciated.

Solution

You don't have to join patterns by \|, grep accepts a newline separated list as well. So you can simply do:

grep -v "$(printf '%s\n' "${arr[@]}")" a.txt | grep error

Proof of concept:

$ arr=(2 4)
$ seq 4 | grep -v "$(printf '%s\n' "${arr[@]}")"
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Answered By - oguz ismail