Tutorial by Examples: bang



You can add an interpreter directive (shebang) to your script. Create a file called hello_world.rb which contains: #!/usr/bin/env ruby puts 'Hello World!' Give the script executable permissions. Here's how to do that in Unix: $ chmod u+x hello_world.rb Now you do not need to call the Ru...
If you need an ActiveRecord method to raise an exception instead of a false value in case of failure, you can add ! to them. This is very important. As some exceptions/failures are hard to catch if you don't use ! on them. I recommended doing this in your development cycle to write all your ActiveRe...
To execute a script file with the bash interpreter, the first line of a script file must indicate the absolute path to the bash executable to use: #!/bin/bash The bash path in the shebang is resolved and used only if a script is directly launch like this: ./script.sh The script must have exe...
To execute a script file with the bash executable found in the PATH environment variable by using the executable env, the first line of a script file must indicate the absolute path to the env executable with the argument bash: #!/usr/bin/env bash The env path in the shebang is resolved and used...
Patterns annotated with a bang (!) are evaluated strictly instead of lazily. foo (!x, y) !z = [x, y, z] In this example, x and z will both be evaluated to weak head normal form before returning the list. It's equivalent to: foo (x, y) z = x `seq` z `seq` [x, y, z] Bang patterns are enabled ...
Given a hello.groovy file with content: #!/usr/bin/env groovy println "Hello world" Can be executed from the command line if given execution permission as $ ./hello.groovy
There are two kinds of programs the kernel knows of. A binary program is identified by it's ELF (ExtenableLoadableFormat) header, which is usually produced by a compiler. The second one are scripts of any kind. If a file starts in the very first line with the sequence #! then the next string has to...

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