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Test if a command outputs an empty string
How can I test if a command outputs an empty string?
11 Answers
11
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Get the client IP address using PHP [duplicate]
... to get the IP address.
The below both functions are equivalent with the difference only in how and from where the values are retrieved.
getenv() is used to get the value of an environment variable in PHP.
// Function to get the client IP address
function get_client_ip() {
$ipaddress = '';
...
How can I check if a command exists in a shell script? [duplicate]
I am writing my first shell script. In my script I would like to check if a certain command exists, and if not, install the executable. How would I check if this command exists?
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How can I check if a single character appears in a string?
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You can use string.indexOf('a').
If the char a is present in string :
it returns the the index of the first occurrence of the character in
the character sequence represented by this object, or -1 if the
character does not occur.
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If vs. Switch Speed
Switch statements are typically faster than equivalent if-else-if statements (as e.g. descibed in this article ) due to compiler optimizations.
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Check if object exists in JavaScript
How do I verify the existence of an object in JavaScript?
18 Answers
18
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PHP check whether property exists in object or class
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property_exists( mixed $class , string $property )
if (property_exists($ob, 'a'))
isset( mixed $var [, mixed $... ] )
if (isset($ob->a))
isset() will return false if property is null
Example 1:
$ob->a = null
var_dump(isset($ob->a)); // false
Example 2: ...
Test if a variable is set in bash when using “set -o nounset”
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#!/bin/bash
set -o nounset
VALUE=${WHATEVER:-}
if [ ! -z ${VALUE} ];
then echo "yo"
fi
echo "whatever"
In this case, VALUE ends up being an empty string if WHATEVER is not set. We're using the {parameter:-word} expansion, which you can look up in man bash under "Param...
How do I drop a function if it already exists?
...imple, but how do I preface the creation of a function with a check to see if it already exists? If it exists, I want to drop and re-create it.
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How do I compare two string variables in an 'if' statement in Bash? [duplicate]
I'm trying to get an if statement to work in Bash (using Ubuntu ):
12 Answers
12
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