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How to make “if not true condition”?
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try
if ! grep -q sysa /etc/passwd ; then
grep returns true if it finds the search target, and false if it doesn't.
So NOT false == true.
if evaluation in shells are designed to be very flexible, and many times doesn't require chains of commands (as you have written).
Also, looking a...
How to test if a double is an integer
Is it possible to do this?
15 Answers
15
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How to dynamically compose an OR query filter in Django?
... Take one Q object from the list
query = queries.pop()
# Or the Q object with the ones remaining in the list
for item in queries:
query |= item
# Query the model
Article.objects.filter(query)
share
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Giving a border to an HTML table row,
Is it possible to border a table row, <tr> in one go instead of giving a border to individual cells, <td> like,
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img src SVG changing the styles with CSS
...isely answer the original question, just:
Open your logo.svg in a text editor.
look for fill: #fff and replace it with fill: #000
For example, your logo.svg might look like this when opened in a text editor:
<svg fill="#000000" height="24" viewBox="0 0 24 24" width="24" xmlns="http://www.w...
What is an index in SQL?
...L server has to walk through the whole table and check every row to see if it matches, which may be a slow operation on big tables.
The index can also be a UNIQUE index, which means that you cannot have duplicate values in that column, or a PRIMARY KEY which in some storage engines defines where in...
What is the correct answer for cout
...d before every value computation and side effect of E2.
Which means that it requires the code to produce result b, which outputs 01.
See P0145R3 Refining Expression Evaluation Order for Idiomatic C++ for more details.
sha...
What is tail recursion?
...rting to learn lisp, I've come across the term tail-recursive . What does it mean exactly?
28 Answers
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Technically what is the main difference between Oracle JDK and OpenJDK? [duplicate]
I have been using OpenJDK for ages, initially for small projects where it has no problems. But since I started to play with it for big toys, I started to notice random/unknown fatal error and crashes (with H.264 codecs, etc.), and it was a nightmare till then to get ride of system crash+fatal errors...
GET URL parameter in PHP
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$_GET is not a function or language construct—it's just a variable (an array). Try:
<?php
echo $_GET['link'];
In particular, it's a superglobal: a built-in variable that's populated by PHP and is available in all scopes (you can use it from inside a function withou...