# Massive \`readstring\` -\> Too many open files
**URL:** https://discourse.julialang.org/t/massive-readstring-too-many-open-files/3426
**Category:** General Usage
**Created:** [April 29, 2017, 3:19am UTC](https://discourse.julialang.org/t/massive-readstring-too-many-open-files/3426 "2017-04-29T03:19:04Z")
**Posts on this page:** 9
**Page:** 1
### Author:  [@ulysses](https://discourse.julialang.org/u/ulysses)
#### Post date: [April 29, 2017, 3:19am UTC](https://discourse.julialang.org/t/massive-readstring-too-many-open-files/3426/1 "2017-04-29T03:19:04Z")
My program processs large amount of files using `readstring`. Eventually it dies with `Too many open files`. I quess the reason is the way `read` function is implemented: it just do `open` but do not `close`, neither use `do` block. Should I report a bug? Or I misunderstand something?
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### Author:  [@yuyichao](https://discourse.julialang.org/u/yuyichao)
#### Post date: [April 29, 2017, 3:49am UTC](https://discourse.julialang.org/t/massive-readstring-too-many-open-files/3426/2 "2017-04-29T03:49:23Z")
`readstring` appears to be properly closing the file [https://github.com/JuliaLang/julia/blob/8eca02717bcea524877fad01aacedc807898bcd1/base/io.jl#L537](https://github.com/JuliaLang/julia/blob/8eca02717bcea524877fad01aacedc807898bcd1/base/io.jl#L537) by using the callback verion. Which function are you calling?
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### Author:  [@ulysses](https://discourse.julialang.org/u/ulysses)
#### Post date: [April 29, 2017, 4:23am UTC](https://discourse.julialang.org/t/massive-readstring-too-many-open-files/3426/3 "2017-04-29T04:23:58Z")
I thought that it is `readstring` from `base/process.jl` which is called. It invokes [`read` which, AFAIS, don’t do close](https://github.com/JuliaLang/julia/blob/8eca02717bcea524877fad01aacedc807898bcd1/base/process.jl#L631).
I’m not sure how Julia decides which of two (io.jl vs. process.jl) `readstring` to call.
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### Author:  [@yuyichao](https://discourse.julialang.org/u/yuyichao)
#### Post date: [April 29, 2017, 5:05am UTC](https://discourse.julialang.org/t/massive-readstring-too-many-open-files/3426/4 "2017-04-29T05:05:31Z")
If you are using the file one then it’s not the one for `AbstractCmd`. See [the doc](https://docs.julialang.org/en/latest/manual/methods.html) for how these works. The one for command is closed after the read.
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### Author:  [@ulysses](https://discourse.julialang.org/u/ulysses)
#### Post date: [April 29, 2017, 4:03pm UTC](https://discourse.julialang.org/t/massive-readstring-too-many-open-files/3426/5 "2017-04-29T16:03:03Z")
Now I see. It seems, that calling `readstring("/path/to/file")` turns into the following chain of calls:
```julia
(1) readstring("/path/to/file") →
(2) open(readstring, "/path/to/file") →
(3) readstring(file_handle) →
(4) read(file_handle) → ...
```
And `open` (2) do `close` handle after `readstring` (3) returns.
It stays unclear though, why many `readstring`s lead to `Too many open files`. I can’t provide minimum working example so far (the program crushed with this is huge). I’ll try to do it asap.
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### Author:  [@ulysses](https://discourse.julialang.org/u/ulysses)
#### Post date: [April 29, 2017, 4:39pm UTC](https://discourse.julialang.org/t/massive-readstring-too-many-open-files/3426/6 "2017-04-29T16:39:56Z")
I found the other place in the project with `open` not balanced with `close`.
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### Author:  [@yuyichao](https://discourse.julialang.org/u/yuyichao)
#### Post date: [April 29, 2017, 4:56pm UTC](https://discourse.julialang.org/t/massive-readstring-too-many-open-files/3426/7 "2017-04-29T16:56:02Z")
For future reference, not sure what OS you are on, at least on linux it is easy to check `/proc/self/fd` and see what are the opened files, that should give you an idea of when/where it happens. I imaging windows/mac have similar tools.
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### Author:  [@ulysses](https://discourse.julialang.org/u/ulysses)
#### Post date: [April 29, 2017, 5:39pm UTC](https://discourse.julialang.org/t/massive-readstring-too-many-open-files/3426/8 "2017-04-29T17:39:23Z")
I’m on Linux. This will be helpful, thank you very much!
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### Author:  [@jameson](https://discourse.julialang.org/u/jameson)
#### Post date: [May 1, 2017, 5:39am UTC](https://discourse.julialang.org/t/massive-readstring-too-many-open-files/3426/9 "2017-05-01T05:39:48Z")
> [@yuyichao](#):
>
> on linux it is easy to check /proc/self/fd and see what are the opened files
`lsof` exists on many UNIX dialects (including mac) to do this in a more general manner