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How do I test if a variable is a number in Bash?
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One approach is to use a regular expression, like so:
re='^[0-9]+$'
if ! [[ $yournumber =~ $re ]] ; then
echo "error: Not a number" >&2; exit 1
fi
If the value is not necessarily an integer, consider amending the regex appropriately; for instance:
^[0-9]+([.][0-9]+)?$
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How can I transition height: 0; to height: auto; using CSS?
...y Chris Jordan in another answer here.
#menu #list {
max-height: 0;
transition: max-height 0.15s ease-out;
overflow: hidden;
background: #d5d5d5;
}
#menu:hover #list {
max-height: 500px;
transition: max-height 0.25s ease-in;
}
<div id="menu">
<a...
In Hibernate Validator 4.1+, what is the difference between @NotNull, @NotEmpty, and @NotBlank?
...he CharSequence, Collection, Map or Array object is not null and size > 0.
@NotBlank: The string is not null and the trimmed length is greater than zero.
To help you understand, let's look into how these constraints are defined and carried out (I'm using version 4.1):
The @NotNull constrain...
Update multiple rows in same query using PostgreSQL
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+50
You can also use update ... from syntax and use a mapping table. If you want to update more than one column, it's much more generaliza...
Random Gaussian Variables
...rand = new Random(); //reuse this if you are generating many
double u1 = 1.0-rand.NextDouble(); //uniform(0,1] random doubles
double u2 = 1.0-rand.NextDouble();
double randStdNormal = Math.Sqrt(-2.0 * Math.Log(u1)) *
Math.Sin(2.0 * Math.PI * u2); //random normal(0,1)
double randNormal =...
git produces Gtk-WARNING: cannot open display
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edited Jun 27 '13 at 7:07
answered Apr 19 '13 at 12:19
J...
What does it mean in shell when we put a command inside dollar sign and parentheses: $(command)
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– Jonathan Leffler
Aug 1 '13 at 4:03
7
Technically, $(echo foo) creates a command substitution,...
Sorting Python list based on the length of the string
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205
When you pass a lambda to sort, you need to return an integer, not a boolean. So your code sho...
How can I filter lines on load in Pandas read_csv function?
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170
There isn't an option to filter the rows before the CSV file is loaded into a pandas object.
Y...
How to copy part of an array to another array in C#?
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int[] b = new int[3];
Array.Copy(a, 1, b, 0, 3);
a = source array
1 = start index in source array
b = destination array
0 = start index in destination array
3 = elements to copy
share
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