Like presented in the title,
What's the opposite of "=~" operator?
I really googled for that and I fund just the following solution: [[ ! $str1 =~ $str2 ]]
Is there any operator that verify the opposite of "=~" operator?
Thanks.
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Armageddon
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1Why do you need it? Doesn't `! (X =~ Y)` suffice? – May 26 '14 at 11:37
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1and why I use that if an operator ready exits? – Armageddon May 26 '14 at 11:40
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@Rhymoid I guess `! X > Y` would suffice but it's nicer to write `X < Y`. – Tom Fenech May 26 '14 at 11:40
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@TomFenech I **really** hope you mean `X <= Y`. – May 26 '14 at 11:42
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4@Rhymoid no, I meant `! X >= Y` :) – Tom Fenech May 26 '14 at 11:44
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@user3629514 Why not using it? Because nobody would understand it. Most languages use and, or, not. That's all you need and many programmers don't even understand xor or bit shifts. My guess for your initial answer would be: use test, it has so many options, nobody knows them all. – usr1234567 May 26 '14 at 11:49
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1@user2799037 this is the problem, I'm not the only one who use my code, and I've to maximize the optimization ... – Armageddon May 26 '14 at 11:52
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1@user3629514: for regular expressions, having a dedicated non-match-operator doesn't optimize anything. – May 26 '14 at 11:54
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CShell has the `!~` operator for this. – Saiansh Singh Jan 16 '22 at 20:12
2 Answers
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There is no opposing operator in bash up to version 4.3 (current at the time of this post).
[[ ! str1 =~ str2 ]] is the way to go.
For such questions, you should use man instead of your favourite search engine. The man page of the tool involved -- bash, in this case -- is authoritative, the 'web is hearsay (unless, of course, it led you to the man page ;-) ).
DevSolar
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Answer is There is no such Operator in bash Which does !~ as its there in perl, if you do not want to use already known ( [[ ! $str1 =~ $str2 ]] ) for the purpose then you shall have to use grep or perl . Something like:
x="I like negation"
y="like"
if [[ $(perl -ne "!/$y/ && print" <(echo $x)) == "$x" ]]; then
echo "Contains"
else
echo "Doesn't contain"
But I don't find any reason to miss !~ in bash as [[ ! $str1 =~ $str2 ]] solves the purpose pretty well. May be that the reason its not there in bash.
Consider the first comment on this Answer from DevSolar, It holds when you will go with grep or perl, which again makes [[ ! $str1 =~ $str2 ]] the best out of available.
PradyJord
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2Hm... calling an external process is hardly an improvement, neither performance- nor readability-wise. – DevSolar May 26 '14 at 13:40