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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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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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How to check if a variable is not null?
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They are not equivalent. The first will execute the block following the if statement if myVar is truthy (i.e. evaluates to true in a conditional), while the second will execute the block if myVar is any value other than null.
The only values that are not truthy in JavaScript are the following (a...
Checking if jquery is loaded using Javascript
I am attempting to check if my Jquery Library is loaded onto my HTML page. I am checking to see if it works, but something is not right. Here is what I have:
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If statement in aspx page
I want to write a basic if statement on my site to display either item 1 or item 2 depending on if a variable is set to true.
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jquery if div id has children
This if -condition is what's giving me trouble:
7 Answers
7
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