That means, you get TWO complete meal plans!
How to add a header? This week I work with several data files and one header file. I just want to insert the contents of the header file on top of each data file: For the sake of the demonstration, I only displayed one file. But you may imagine I have many of them — too many for considering manual editing.
Value Month, Year, Est. Value As you can see, I really need your help here — both to explain to me what was going on and to help me in solving that issue. Few details To create this challenge, I Challenge 8 GNU Bash, version 4. If you run that in a terminal, you will be able to reproduce exactly the same result as displayed in the challenge illustration assuming you are using the same software version Challenge 8 me: In a pipeline, all commands are launched in parallel.
That means the cat command reading the DATA01 file and the tee command overwriting that same file are launched simultaneously. This is really a race condition. On my system, tee had time to overwrite the destination file before cat had the opportunity to read it.
To illustrate that, we can delay the commands and see the output is clearly dependent on the timing: Value I would have a similar issue albeit deterministic this time using the simpler: So the content of the file is lost long before cat had even the opportunity to read it. How to fix that? Obviously, no one would ever use the sleep hack in a real situation.
But this is not an issue: Well, while being rudimentary, this solution has a nice feature: A somewhat similar solution, but avoiding to create a temporary file visible on the filesystem would obtain first a file descriptor to read from the original file before overwriting it: Please note this solution is no longer atomic in the sense used above.
Anyways, Kudos to Adithya Kiran Gangu for having proposed that solution! Using sed While encountering similar problems for the first time, my idea was to use sed. In fact, to achieve that, we will need a little bit of magic: So, when encountering that command, sed ends processing of line 1. But the line 1 itself is not sent to the output.
It is kept in the sed buffer. Then sed reads the next line of input, append it to the buffer, and as we do not have any rule for line 2, process it as usual by sending its buffer to the output remember at that stage, the buffer contains both line 1 and line 2.
This solution has a major drawback: If the data file contains only one line, this will fail miserably.
Using ed or ex We have very few occasions of using ed or its cousin ex. Both are line oriented editors. Their behavior is very similar to vi in that sense you load file into memory, and send commands to the editor to modify that file.
The only difference here is we will script the commands instead of sending them interactively. This works great, but as we have to load the whole file into memory which could be an issue for very large files.
As always, those are probably only a subset of all possible solutions. And stay tuned for more fun!Challenge 8.
likes. To Infinity and beyond！到達無窮，超越無窮. Sign in - Google Accounts. Fortnite: Use A Rift Spawn Locations (Season 5, Week 8 Challenge Guide) It's time to earn some more Battle Stars.
Challenge Turku is a true city race in the very heart of Turku. Learn more about the legendary triathlon event in Finland! Top 8 Challenge. likes.
The Top 8 Challenge is designed to help raise awareness for those living with an Eosinophilic Gastrointestinal Disorder (EGID).
Challenge program. Cadets immersed in a group-living environment demonstrate mastery of this component as they develop and define moral standards, apply ethical decisions, and collaborate with their peers.