It seems to me that if there is no newline, it should still read the result. On the other hand, it also says:. It is not a relaxation of the requirement for standard input to be a text file. A file that contains characters organized into zero or more lines. Note Gordon Davisson 's answer. A simple test shows that his observation is accurate:.
I'm still surprised to find that the shells drop the last segment it can't be called a line because it doesn't end with a newline of the input, but there might be sufficient justification in POSIX to do so. And clearly it is best to ensure that your text files really are text files ending with a newline. According to the POSIX spec for the read command , it should return a nonzero status if "End-of-file was detected or an error occurred.
And to make it work with files without a newline at end reposting my solution from here :. This will ensure that all the lines that was previously in the file will be read.
We need to pass -e argument to echo to enable interpretation of escape sequences. Use sed to match the last line of a file, which it will then append a newline if one does not exist and have it do an inline replacement of the file:.
The code is from this stackexchange link. Note: I have added empty single quotes to -i '' because, at least in OS X, -i was using -e as a file extension for the backup file. I would have gladly commented on the original post but lacked 50 points. Perhaps this will gain me a few in this thread, thanks. This misses the last line, which makes sense since read only gets input that ends with a newline.
I had a similar issue. I was doing a cat of a file, piping it to a sort and then piping the result to a 'while read var1 var2 var3'. I also ran into the issue where I couldnt get the last line to print to the report. Stack Overflow for Teams — Collaborate and share knowledge with a private group.
Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. If dos2unix is not present on your system you can use the package manager of your distribution to install it. If you are interested I have written an article that explains the basics of Bash script arguments. I want to help you in your journey to become a Super Developer! Your email address will not be published. Save my name, email, and website in this browser for the next time I comment. This website uses cookies so that we can provide you with the best user experience possible.
Cookie information is stored in your browser and performs functions such as recognising you when you return to our website and helping our team to understand which sections of the website you find most interesting and useful. From the above command, you will get the following response on the terminal window:. Create a bash file and then add the below-mentioned code in this file to read the file content. Now, using the while loop we will read each line from a file with a particular line number.
Save the file with a name OSinfo. In a bash file, you need to add the following code script. The loop is one of the most fundamental and powerful constructs in computing, because it allows us to repeat a set of commands, as many times as we want, upon a list of items of our choosing. Much of computational thinking involves taking one task and solving it in a way that can be applied repeatedly to all other similar tasks, and the for loop is how we make the computer do that repetitive work:.
Unlike most of the code we've written so far at the interactive prompt, a for-loop doesn't execute as soon as we hit Enter :. We can write out as many commands as we want in the block between the do and done keywords:. Only until we reach done , and hit Enter , does the for-loop do its work. This is fundamentally different than the line-by-line command-and-response we've experienced so far at the prompt.
And it presages how we will be programming further on: less emphasis on executing commands with each line, and more emphasis on planning the functionality of a program, and then executing it later. A command substitution can be used to generate the items that the for loop iterates across:.
If you need to read a list of lines from a file, and are absolutely sure that none of the lines contain a space within them:. A read-while loop is a variation of the above, but is safer for reading lines from a file:.
Let's start from a beginning, with a very minimal for loop, and then built it into something more elaborate, to help us get an understanding of their purpose. Did that seem pretty worthless? Yes it should have. I wrote four lines of code to do what it takes a single line to do, echo 'Hi'. It's hard to tell, but a "loop" did execute. It just executed once. OK, so how do we make it execute more than one time? Add more space-separated elements to the right of the in keyword. Let's add four more 1 's:.
OK, not very exciting, but the program definitely seemed to at least loop : four 1 's resulted in four echo commands being executed. What happens when we replace those four 1 's with different numbers?
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