4 ms·

Does someone know a ressource where I can easily learn how to switch from Bash to Go? To give some context: When it comes to serious programs I use Go already,

Does someone know a ressource where I can easily learn how to switch from Bash to Go? To give some context: When it comes to serious programs I use Go already, but often I just want to code a little script to watch a website for changes for example: #!/usr/bin/env bash url="https://example.com" mem="memory.txt" oldsum="$(cat "$mem")" newsum="$(curl -sL "$url" | sha512sum)" if [ "$oldsum" != "$newsum" ]; then xmpp_notify "$url changed" echo "$newsum" > "$mem" fi I haven't tried it yet, but in my mind it feels like writing such a program would be more time consuming/complex in Go than writing it in bash. Neverthelss, I feel like Go is overall a much better language than Bash (with all those quotes), so I would like to transition to writing more short programs in Go and for that I would like to learn how to do things like reading/writing/grepping files as easily in Go as I do it in Bash. Any idea if someone wrote some hints together already?

chomp 8y ago
The benefit of bash is that it has system binaries as first class citizens; you can leverage the hundreds of thousands of lines of GNU projects with a single keyword. It's hard to beat that expressiveness. Saying "Go is overall a much better language" is like saying a wrench is a better tool than a screwdriver. You should keep both in your toolbelt and switch out when the need arises. For your question, start with the regexp and os package, learn how to open a file, read in the contents, and then while iterating over the contents, apply a regex to the text. That should get you to the point that you can search plaintext for character strings. Good luck.
rezeroed 8y ago
Go is the wrong tool for that. I'm no fan of bash, but it's often the the quick, clear (enough) solution for small tasks. I'm not a python dev - maybe that would be a suitable compromise?
baq 8y ago
i'd say bash is the perfect tool for the problem that you demonstrated. go may be a better language but it's just another tool.
- IshKebab 8y ago
  Depends how much you care about robustness. If the answer is "more than zero" than Bash is a terrible tool.
ainar-g 8y ago
As a professional gopher, don't. Just a few months ago I replaced an almost 100-line Go "script" with two lines in the Makefile. The fact that Go is great for big projects doesn't automatically make it good for everything. Go is for programs, not scripts.
- arendtio 8y ago
  Thanks for your warning :-) My problems come from the other end: My Bash scripts tend to become larger. A few weeks ago I wrote a 'cache' utility function (very useful to cache curl requests for example). A few days ago I wanted to use it in a second script was just about to write a package manager for bash modules... I think that is the kind of situation you are getting into when the line count of a bash script increases and you are trying to do proper software development ;-) So I am not going to build every script in Go from today on, but I would like to learn a bit more on when Go is a viable alternative to Bash.
swaroop 8y ago
Or you could use Python with https://pypi.org/project/plumbum/ https://pypi.org/project/plumbum/ :)
IshKebab 8y ago
Writing a program like that would not be too difficult in Go. It's something like this: func main() { url := "https://example.com" mem := "memory.txt" oldsum, err := ioutil.ReadFile(mem) if err != nil { log.Fatal(err) } // Download URL resp, err := http.Get(url) if err != nil { log.Fatal(err) } defer resp.Body.Close() body, err := ioutil.ReadAll(resp.Body) if err != nil { log.Fatal(err) } // Hash it newsum := sha512.Sum512(body) if oldsum != newsum { err = exec.Command("xmpp_notify", url + " changed").Run() if err != nil { log.Warn(err) } err = ioutil.Write(mem, newsum) if err != nil { log.Error(err) } } } Don't listen to the naysayers. Go is fantastic for scripts like this - it's really good at network stuff, has a ton of built in functions, etc. And you get actual robustness and error checking that isn't a complete joke. Look how many ways your Bash script could fail! That's fine if you're literally watching the output with your eyes. If not it's going to cause issues when `curl` fails for example. The only downside really is that you have to compile the Go code, which is fast but not as fast as just interpreting a Bash script (the first time). Another possible issue is executable size - if you have a lot of Go scripts they may take up a fair bit of space. I wish Go had an interpreter / JIT mode for scripts. Edit: Before someone says "but that's 3 times longer than the bash code!" please write the equivalent Bash code that has proper error checking.
- boris 8y ago
  Just add this as a second line? trap "exit 1" ERR
  - majewsky 8y ago
    I think you mean: set -euo pipefail
- h1d 8y ago
  That is so repetitive to handle errors. Doesn't go have a cleaner way of handling errors than making the code look far less readable without unified error handling like exceptions?
dilap 8y ago
I love Go and use it for allllmost everything, but I think bash is still better for something like this. The ease with which it can run programs and capture output is the killer feature. I'd love to see some future bash like language that's strongly typed, has a consistent and simple syntax, but retains these advantages.
lalaithion 8y ago
for me, I use bash for anything less than 10 lines long, python for anything between 10 and 500 lines, and then I switch to a heavier programming language for anything longer.
watshn 8y ago
Being such a concise language, Haskell could be a good option here. You can do quick scripting while still having a powerful type system (especially compared to Go's) backing you up. I somewhat quickly typed this code up and haven't tested it, but it should replicate that bash script pretty closely: #!/usr/bin/env stack -- stack script --resolver=lts-12.2 import System.Process (system) import Control.Lens import Crypto.Hash.SHA256 import qualified Data.Bytestring.Lazy as B import Network.Wreq url = "https://example.com" mem = "memory.txt" main = do oldsum <- B.readFile mem newsum <- (hashLazy . view responseBody) <$> get url when (oldsum /== newsum) $ do exitCode <- system $ "xmpp_notify " ++ url ++ " changed" B.writeFile mem newsum I didn't make use of it, but there's also the Turtle library which aims to provide a fairly solid shell scripting experience, providing a lot of coreutils as simple Haskell functions. You also get a REPL in the form of GHCI, which comes default in Haskell installations.

chomp 8y ago

The benefit of bash is that it has system binaries as first class citizens; you can leverage the hundreds of thousands of lines of GNU projects with a single keyword. It's hard to beat that expressiveness. Saying "Go is overall a much better language" is like saying a wrench is a better tool than a screwdriver. You should keep both in your toolbelt and switch out when the need arises. For your question, start with the regexp and os package, learn how to open a file, read in the contents, and then while iterating over the contents, apply a regex to the text. That should get you to the point that you can search plaintext for character strings. Good luck.

rezeroed 8y ago

Go is the wrong tool for that. I'm no fan of bash, but it's often the the quick, clear (enough) solution for small tasks. I'm not a python dev - maybe that would be a suitable compromise?

baq 8y ago

i'd say bash is the perfect tool for the problem that you demonstrated. go may be a better language but it's just another tool.

IshKebab 8y ago
Depends how much you care about robustness. If the answer is "more than zero" than Bash is a terrible tool.

ainar-g 8y ago

As a professional gopher, don't. Just a few months ago I replaced an almost 100-line Go "script" with two lines in the Makefile. The fact that Go is great for big projects doesn't automatically make it good for everything. Go is for programs, not scripts.

arendtio 8y ago
Thanks for your warning :-) My problems come from the other end: My Bash scripts tend to become larger. A few weeks ago I wrote a 'cache' utility function (very useful to cache curl requests for example). A few days ago I wanted to use it in a second script was just about to write a package manager for bash modules... I think that is the kind of situation you are getting into when the line count of a bash script increases and you are trying to do proper software development ;-) So I am not going to build every script in Go from today on, but I would like to learn a bit more on when Go is a viable alternative to Bash.

swaroop 8y ago

Or you could use Python with https://pypi.org/project/plumbum/ https://pypi.org/project/plumbum/ :)

IshKebab 8y ago

Writing a program like that would not be too difficult in Go. It's something like this: func main() { url := "https://example.com" mem := "memory.txt" oldsum, err := ioutil.ReadFile(mem) if err != nil { log.Fatal(err) } // Download URL resp, err := http.Get(url) if err != nil { log.Fatal(err) } defer resp.Body.Close() body, err := ioutil.ReadAll(resp.Body) if err != nil { log.Fatal(err) } // Hash it newsum := sha512.Sum512(body) if oldsum != newsum { err = exec.Command("xmpp_notify", url + " changed").Run() if err != nil { log.Warn(err) } err = ioutil.Write(mem, newsum) if err != nil { log.Error(err) } } } Don't listen to the naysayers. Go is fantastic for scripts like this - it's really good at network stuff, has a ton of built in functions, etc. And you get actual robustness and error checking that isn't a complete joke. Look how many ways your Bash script could fail! That's fine if you're literally watching the output with your eyes. If not it's going to cause issues when `curl` fails for example. The only downside really is that you have to compile the Go code, which is fast but not as fast as just interpreting a Bash script (the first time). Another possible issue is executable size - if you have a lot of Go scripts they may take up a fair bit of space. I wish Go had an interpreter / JIT mode for scripts. Edit: Before someone says "but that's 3 times longer than the bash code!" please write the equivalent Bash code that has proper error checking.

boris 8y ago
Just add this as a second line? trap "exit 1" ERR
- majewsky 8y ago
  I think you mean: set -euo pipefail
h1d 8y ago
That is so repetitive to handle errors. Doesn't go have a cleaner way of handling errors than making the code look far less readable without unified error handling like exceptions?

dilap 8y ago

I love Go and use it for allllmost everything, but I think bash is still better for something like this. The ease with which it can run programs and capture output is the killer feature. I'd love to see some future bash like language that's strongly typed, has a consistent and simple syntax, but retains these advantages.

lalaithion 8y ago

for me, I use bash for anything less than 10 lines long, python for anything between 10 and 500 lines, and then I switch to a heavier programming language for anything longer.

watshn 8y ago

Being such a concise language, Haskell could be a good option here. You can do quick scripting while still having a powerful type system (especially compared to Go's) backing you up. I somewhat quickly typed this code up and haven't tested it, but it should replicate that bash script pretty closely: #!/usr/bin/env stack -- stack script --resolver=lts-12.2 import System.Process (system) import Control.Lens import Crypto.Hash.SHA256 import qualified Data.Bytestring.Lazy as B import Network.Wreq url = "https://example.com" mem = "memory.txt" main = do oldsum <- B.readFile mem newsum <- (hashLazy . view responseBody) <$> get url when (oldsum /== newsum) $ do exitCode <- system $ "xmpp_notify " ++ url ++ " changed" B.writeFile mem newsum I didn't make use of it, but there's also the Turtle library which aims to provide a fairly solid shell scripting experience, providing a lot of coreutils as simple Haskell functions. You also get a REPL in the form of GHCI, which comes default in Haskell installations.