Bash Script For Mac Os Convert Julian Date To A Calendar Date

BASH SCRIPT CONVERT JULIAN DATE TO A CALENDAR DATE MAC OS X IS A

Bash Script Convert Julian Date To A Calendar Date Mac OS X Is A

We'll go through a variety of different ways that variables have their data set and ways we can then use them.Mac OS X is a developers dream, packing in Perl, Python, Ruby, C, C++. These variables can be very useful for allowing us to manage and control the actions of our Bash Script. For those of you that haven't, think of a variable as a temporary store for a simple piece of information. MIDNIGHTSECONDS : Returns an integer value in the range 0-86400 representing the number of seconds between midnight and the time value specified in the argument.For those of you that have dabbled in programming before, you'll be quite familiar with variables. (the start of Julian calendar) to the date value specified in the argument. JULIANDAY: Returns an integer value representing the number of days from January 1, 4712, B.C.

As such there is a bit of reading in this section but if you take the time to go through and understand it you will be thankful you did later on when we start dabbling in more complex scripts. Variables are one of those things that are actually quite easy to use but are also quite easy to get yourself into trouble with if you don't properly understand how they work. To have these sensors available in your installation, add the following to your configuration.yaml file (each option creates a separate sensor that contains appropriate data, e.g., sensor.date for the date.

For every variable it has identified, it replaces the variable name with its value. Before Bash interprets (or runs) every line of our script it first checks to see if any variable names are present. You will see examples of both below.To read the variable we then place its name (preceded by a $ sign) anywhere in the script we would like. The most common are to set the value directly and for its value to be set as the result of processing by a command or program. There are two actions we may perform for variables:Variables may have their value set in a few different ways. In.A variable is a temporary store for a piece of information.

For instance we could run the command ls -l /etc. This is made possible as the substitution is done before the command is run.Command line arguments are commonly used and easy to work with so they are a good place to start.When we run a program on the command line you would be familiar with supplying arguments after it to control its behaviour. A variable may be placed anywhere in a script (or on the command line for that matter) and, when run, Bash will replace it with the value of the variable. They can be all uppercase, all lowercase, or a mixture.

This can be useful for keeping track of results of commands and being able to refer to and process them later.There are a few ways in which variables may be set (such as part of the execution of a command) but the basic form follows this pattern:This is one of those areas where formatting is important. Setting Our Own VariablesAs well as variables that are preset by the system, we may also set our own variables. As we progress to more complex scripts in later sections you will see examples of how they can be useful. These are automatically set by the system when we run our script so all we need to do is refer to them.If you type the command env on the command line you will see a listing of other variables which you may also refer to.Some of these variables may seem useful to you now. To do this we use the variables $1 to represent the first command line argument, $2 to represent the second command line argument and so on. We can do similar with our bash scripts.

So although the variables will have the same name they exist in separate processes and so are unrelated to each other.Exporting variables is a one way process. What actually happens when we export a variable is that we are telling Bash that every time a new process is created (to run another script or such) then make a copy of the variable and hand it over to the new process. This makes their purpose easier for you to remember.Here is a simple example to illustrate their usage.The output above may seem unexpected. You should always make sure variable names are descriptive. We also leave off the $ sign from the beginning of the variable name when setting it.Variable names may be uppercase or lowercase or a mixture of both but Bash is a case sensitive environment so whenever you refer to a variable you must be consistent in your use of uppercase and lowercase letters.

SummaryFormatting The presence or absence of spaces is important. Then you could easily call that script from within other scripts you create whenever you would like to take a snapshot of a set of files. For instance you could create a script which will make a dated (ie todays date prepended to the filename) copy of all filenames exported on a certain variable. Sometimes you may wish to break a particular task down into several separate scripts however to make it easier to manage or to allow for reusability (which is always good).

Hint: Piping will be useful here. There is a file containing a list of words on your system (usually /usr/share/dict/words or /usr/dict/words). Create a script which will print a random word. A good place to start is to create a simple script which will accept some command line arguments and echo out some details about them (eg, how many are there, what is the secone one etc).

If our file was named file1.txt it would create a copy such as _file1.txt. Now let's create a script which will take a filename as its first argument and create a dated copy of the file. This will help you get a feel for how exporting variables works. Take a copy of the two files script1.sh and script2.sh above then experiment by tweaking them and running them and observing the output. Hint: Grep may be useful here.

(The command xargs may be useful here. Challenge: Now see if you can expand the previous question to accept a list of files on the command line and it will create a named copy of all of them. File1_.txt (The command basename can be useful here.) Challenge: To make it a bit harder, see if you can get it so that the date is after the name of the file (eg.

Bash Script For Mac Os Convert Julian Date To A Calendar Date