Then I can be 100% certain I’ll find no reasonable error handling in them, obscure race conditions and since it’ll then be “vendor-style” also not be allowed to replace and fix the crap. Oh and not to mention Python & Ruby code with the slight version regressions where suddenly an api query stops working because a 3rd software upgraded a 2nd lib. Always happy to find scripts in higher level languages like this.
Этот скрипт содержит только две строки. Первая строка сообщает системе о том, какая программа используется для запуска файла. Вторая строка — это единственное действие, которое выполняется этим скриптом, он собственно печатает ‘Hello world.
The simplest and most widely available method to get user input at a shell prompt is the read command. The best way to illustrate its use is a .
But what if we want to use different values for our variables every-time we are running our script. Up until now, we were using variables that has values assigned into the script itself. For ex, when we are doing arithemetic operation or when we have created a script to take backup of files & want to define which files needs to be backed up.
Using the read built-in
command; 8. Using the file descriptors to read from and write to multiple
files . Bash Guide for Beginners.
However, there are a few things you should know when writing scripts that you expect to work well. Don’t think bash is a programming language. You might add your own items to this list, but this one is what comes to my mind:. It has arrays, loops, sockets, regular expression matching, file I/O, and lots more.
There are a lot of tricks to writing bash scripts that are portable. However, if you are distributing scripts to machines you don’t control, you might consider searching the internet about bash script portability. I don’t care about those in this context because if I’m deploying an embedded system on a Raspberry Pi, I will control the configuration so that I know where /tmp is and where bash is located and what version of different programs are available.
It's hard to write a bash script of much import without using a pipe or two. Named pipes, on the other hand, are much rarer.
Of course, if you need wildcards, you can’t do this — at least not for the part of the script that uses them. For example, using “set -o noglob” will prevent bash from expanding wildcards. You should consider turning off features you don’t need, especially if taking input from outside your script. You can also use “shopt -s failglob” which will cause wildcards to throw an error, if you want to secure your script.
They are the most convenient for users as the data will be stored in their command history so they can easily return to it. Maybe you want it to run periodically using CRON). It is also the best approach if your script may be called by other scripts or processes (eg. You should normally favor command line arguments wherever possible.
Anywhere else – no of course not. At a startup we rpm-build ruby in-house because there’s no source for a current & secure ruby on centos (the languages team itself delivers an outdated one)
I dislike python for systems code because it encourages laziness on the error handling. Yep, only systems I’ve seen where you could just slap on a new lang env was startup envs, like the ultra-hobbyist way of things. Though in fairness, Python has its place as a default now, and Ruby *would have* if not for the versions.
Для этого служит специальная конструкция, называемая shebang: #. В простейшем случае, скрипт — простой список команд, записанный в файл. Символ # задаёт комментарий, но в данном случае shebang означает, что после этого спецсимвола находится путь к интерпретатору для исполнения сценария. Командный процессор должен знать, что он должен этот файл обработать, а не просто прочесть его содержимое.