Note: If you need to prevent a variable to be used below a certain point in the code, you can create a scope for it using braces, i. It is not necessary and idiomatic to set it explicitly to undef.
Then the program should check if the variable is undefined. Get rid of unused variables and modules. In some development phases and situation, using time on removing unused variables can be considered premature. But in general, unused variables will confuse others that try to read your code. Example from Line The same is true about unused modules. Remember to close files when you are finished with them.
This is a general advice. It is not strictly necessary to do this since lexical filehandles will get automatically closed when they go out of scope. See How severe is it if we do not close a file in Perl?
Example: on line you open two files but you never close them. Reading a filehandle line by line The idiomatic way of doing this is in a while loop using the diamond operator. Example: On lines Also see the caveats in the documentation for eof for more information about why it might not be a good idea to use eof in this case. Example: Line I am not sure what you are trying to do here.
Difference between grep and all : grep says if at least one element in a list matches, all in List::Util tells you if all elements in a list match.
Use of warnings flag in file shebang. The use of -w in the main script shebang! It also only applies to the lexical scope you are in, while -w will apply even to modules you load that don't expect to have warnings enabled. See Is there a difference between use warnings and -w? Indirect object syntax when creating objects : Even though Perl supports the "indirect object" type of method invocation syntax, it is in general discouraged according to perlobj.
A logical error. On line you are computing the number of unique IDs inside the loop that is creating the IDs. It is not possible to know the number of unique IDs until after the loop has finished. So the statement should be put after the loop instead. For example line The code presented below is only a first step towards code improvements.
It illustrates the proposed refactorization. It makes no attempt to optimize anything. Hope this can be a good starting point for you. Good luck! Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams?
Learn more. Asked 5 years, 3 months ago. Active 5 years, 2 months ago. Viewed times. Improve this question. You didn't mention how big are your CSV files. Comma in the field Every time you get a CSV file you can use this script to add up the values in the 3rd column. Unfortunately at some point you get warnings while running your script. This is totally normal within the "standard" of CSV, but our script cannot properly handle the situation. It just cuts where it finds the separator character.
We need a more robust solution to read CSV files. Even if you don't know what OOP is, you don't have to worry. We won't really learn OOP at this point, we'll just use the module.
We learn a little more syntax and a few expression, just so, that people who are familiar with object oriented programming can connect to their knowledge. It provides a set of new functionality, namely reading, parsing and writing CSV files. Perl programmers call these 3rd-party extension modules, though people coming from other languages might be more familiar with words such as library or extension.
At this point I assume you already have the module installed on your computer. We discuss separately how to install it. First we need to load the module using use Text::CSV;.
We don't need to say what to import as this module does not export anything anyway. It works in an object oriented way: you need to create and instance and use that instance. The module itself, Text::CSV is the class and you can create an instance, also called object, by calling the constructor.
In Perl there is no strict rule how to name the constructor but nevertheless most people use the name "new". This call creates an object setting the separator character to be comma ,. An object is just a scalar value. Actually comma being the separator character is the default, but it seems it is clearer if I set it explicitly. The Text::CSV module does not have a split function. In order to split the code you need to call the "parse function" - or, if we want to use the OOP phrase - the "parse method".
It will not return the pieces. It will return true or false depending on its success or failure to parse the string. One common case when it would fail is if there is only a single quotation character. In awk.. Code :. Let say my csv file name is fps. Last edited by Franklin52; at AM.. Reason: Please use code tags for code and data samples, thank you. Corrected the filename and now try with the below command Code :.
I try the code and name the perl program as ami. Im running this perl script on windows 7 and I already installed active perl on my pc.
Seems like nothing happened in csv file. Join Date: Apr Halo itkamaraj I try to run this code ami. How to calculate average of csv using shell scripting?
Hi, I need to calculate the average of the following values using shell scripitng. Can anyone please suggest a solution? How to calculate avg values of csv file using shell scripting.? How to calculate average of two columns and copy into another file?
Hi, I need help with the awk command. I have a folder with aprox files each one with two columns and I want to print in a new file, the average of column 1 and average of column 2 and the name of each file. Input files are: File 99 20 99 50 99 50 99 File Perl script to modify csv file.
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