# What is an idiomatic Julia code for file I/O with exceptions handled?
**URL:** https://discourse.julialang.org/t/what-is-an-idiomatic-julia-code-for-file-i-o-with-exceptions-handled/3361
**Category:** General Usage
**Tags:** question, io
**Created:** [April 24, 2017, 10:47pm UTC](https://discourse.julialang.org/t/what-is-an-idiomatic-julia-code-for-file-i-o-with-exceptions-handled/3361 "2017-04-24T22:47:11Z")
**Posts on this page:** 10
**Page:** 1
### Author:  [@pauljurczak](https://discourse.julialang.org/u/pauljurczak)
#### Post date: [April 24, 2017, 10:47pm UTC](https://discourse.julialang.org/t/what-is-an-idiomatic-julia-code-for-file-i-o-with-exceptions-handled/3361/1 "2017-04-24T22:47:12Z")
What is an idiomatic Julia code for `tryOpen` function below, which tests if 2 files can be opened and handles all exceptions? I’m looking for code replacing the comments or totally different code structure, if needed.
```julia
function tryOpen(fileName1, fileName2)
try
f1 = open(fileName1)
f2 = open(fileName2)
println("$fileName1 and $fileName2 can be opened")
catch
#print open file names
finally
#close opened files
end
end
```
---
### Author:  [@stevengj](https://discourse.julialang.org/u/stevengj)
#### Post date: [April 24, 2017, 11:17pm UTC](https://discourse.julialang.org/t/what-is-an-idiomatic-julia-code-for-file-i-o-with-exceptions-handled/3361/2 "2017-04-24T23:17:35Z")
> [@pauljurczak](#):
>
> open(fileName1)
If you want to just open and then (if successful) immediately close the file, you can do `open(f->nothing, filename)`. This is equivalent to
```julia
open(filename) do f
nothing
end
```
which ensures that the file is closed immediately (as opposed to waiting until garbage-collection happens). Or you can pass any other do-nothing function for the first argument, e.g. `open(identity, filename)`
Putting it together, you can do:
```julia
function isopenable(filenames)
try
open(identity, filename)
return true
catch
return false
end
end
```
To try multiple filenames, I would normally suggest just `isopenable(filename1) && isopenable(filename2)`, though of course you could define
```julia
isopenable(filenames...) = all(isopenable, filenames)
```
---
### Author:  [@stevengj](https://discourse.julialang.org/u/stevengj)
#### Post date: [April 24, 2017, 11:30pm UTC](https://discourse.julialang.org/t/what-is-an-idiomatic-julia-code-for-file-i-o-with-exceptions-handled/3361/3 "2017-04-24T23:30:15Z")
(Note that there is a built-in function `isfile` if you just want to check whether a file exists, or alternatively `isfile(filename) || islink(filename)`, and you can check `uperm(filename)` for read permissions.)
---
### Author:  [@pauljurczak](https://discourse.julialang.org/u/pauljurczak)
#### Post date: [April 24, 2017, 11:33pm UTC](https://discourse.julialang.org/t/what-is-an-idiomatic-julia-code-for-file-i-o-with-exceptions-handled/3361/4 "2017-04-24T23:33:44Z")
> [@stevengj](#):
>
> open(f-\>nothing, filename)
This code will throw uncatched exception when file doesn’t exist.
My question is about acquiring/opening a group of resources, which may throw an exception. I would like to know in `catch` and `finally` blocks, which ones were safely opened. This can be done with a bunch of extra status variables, one per resource, but I wonder if there is a way to avoid them. File opening is just an example of acquiring a resource.
---
### Author:  [@stevengj](https://discourse.julialang.org/u/stevengj)
#### Post date: [April 24, 2017, 11:41pm UTC](https://discourse.julialang.org/t/what-is-an-idiomatic-julia-code-for-file-i-o-with-exceptions-handled/3361/5 "2017-04-24T23:41:23Z")
> [@pauljurczak](#):
>
> This code will throw uncatched exception when file doesn’t exist.
That’s why I put it in a `try` block.
> [@pauljurczak](#):
>
> My question is about acquiring/opening a group of resources, which may throw an exception.
Normally when you acquire a resource, you will associate some kind of handle object with it, e.g. an `IOStream` object for opening a file. You could always initialize these handles to some sentinel value, e.g. `IOStream("")`. In the `catch` block, you will know if they were successfully opened if they are different from the sentinel value.
---
### Author:  [@pauljurczak](https://discourse.julialang.org/u/pauljurczak)
#### Post date: [April 24, 2017, 11:46pm UTC](https://discourse.julialang.org/t/what-is-an-idiomatic-julia-code-for-file-i-o-with-exceptions-handled/3361/6 "2017-04-24T23:46:55Z")
> [@stevengj](#):
>
> IOStream(“”)
Thanks, that’s what I was looking for. Beginner’s problem.
---
### Author:  [@jameson](https://discourse.julialang.org/u/jameson)
#### Post date: [April 25, 2017, 5:46pm UTC](https://discourse.julialang.org/t/what-is-an-idiomatic-julia-code-for-file-i-o-with-exceptions-handled/3361/7 "2017-04-25T17:46:55Z")
To avoid confusing the code reader (and allocating an unnecessary object), I recommending using a sentinel singleton value like `nothing`.
---
### Author:  [@rafael.guerra](https://discourse.julialang.org/u/rafael.guerra)
#### Post date: [May 31, 2021, 8:26am UTC](https://discourse.julialang.org/t/what-is-an-idiomatic-julia-code-for-file-i-o-with-exceptions-handled/3361/8 "2021-05-31T08:26:08Z")
Where in Julia"s official docs may the answer to OP"s essential question be found?
Thank you.
---
### Author:  [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)
#### Post date: [May 31, 2021, 9:33am UTC](https://discourse.julialang.org/t/what-is-an-idiomatic-julia-code-for-file-i-o-with-exceptions-handled/3361/9 "2021-05-31T09:33:00Z")
[https://docs.julialang.org/en/v1/manual/control-flow/#The-try/catch-statement](https://docs.julialang.org/en/v1/manual/control-flow/#The-try/catch-statement)
But please consider not reviving ancient topics without a good reason.
---
### Author:  [@rafael.guerra](https://discourse.julialang.org/u/rafael.guerra)
#### Post date: [May 31, 2021, 9:51am UTC](https://discourse.julialang.org/t/what-is-an-idiomatic-julia-code-for-file-i-o-with-exceptions-handled/3361/10 "2021-05-31T09:51:52Z")
Sorry, but cannot even find half of the content posted above.