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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...
Checking from shell script if a directory contains files
From a shell script, how do I check if a directory contains files?
26 Answers
26
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How to detect Windows 64-bit platform with .NET?
...onment.Is64BitOperatingSystem.
IntPtr.Size won't return the correct value if running in 32-bit .NET Framework 2.0 on 64-bit Windows (it would return 32-bit).
As Microsoft's Raymond Chen describes, you have to first check if running in a 64-bit process (I think in .NET you can do so by checking IntP...
How do I get the application exit code from a Windows command line?
...nning a program and want to see what its return code is (since it returns different codes based on different errors).
7 Ans...
Inverse dictionary lookup in Python
...as a .index method on lists the returns the first found index with the specified value or an exception if not found... any reason why such a semantic could not be applied to dictionaries?
– Brian Jack
Jun 22 '12 at 15:27
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If table exists drop table then create it, if it does not exist just create it
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Just put DROP TABLE IF EXISTS `tablename`; before your CREATE TABLE statement.
That statement drops the table if it exists but will not throw an error if it does not.
s...
Is the ternary operator faster than an “if” condition in Java [duplicate]
I am prone to " if-conditional syndrome " which means I tend to use if conditions all the time. I rarely ever use the ternary operator. For instance:
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How to exit if a command failed?
...am a noob in shell-scripting. I want to print a message and exit my script if a command fails. I've tried:
8 Answers
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Removing all empty elements from a hash / YAML?
...dd a compact method to Hash like this
class Hash
def compact
delete_if { |k, v| v.nil? }
end
end
or for a version that supports recursion
class Hash
def compact(opts={})
inject({}) do |new_hash, (k,v)|
if !v.nil?
new_hash[k] = opts[:recurse] && v.class == Hash...
How to know if user is logged in with passport.js?
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If user is logged in, passport.js will create user object in req for every request in express.js, which you can check for existence in any middleware:
if (req.user) {
// logged in
} else {
// not logged in
}
You ca...