# Is it possible to get an exception message as a string?

**URL:** https://discourse.julialang.org/t/is-it-possible-to-get-an-exception-message-as-a-string/3201
**Category:** General Usage
**Tags:** exception
**Created:** [April 13, 2017, 1:06pm UTC](https://discourse.julialang.org/t/is-it-possible-to-get-an-exception-message-as-a-string/3201 "2017-04-13T13:06:57Z")
**Posts on this page:** 5
**Page:** 1

<div class="post-metadata">

### Author: ![izaid](https://avatars.discourse-cdn.com/v4/letter/i/ee7513/32.png) [@izaid](https://discourse.julialang.org/u/izaid)
#### Post date: [April 13, 2017, 1:06pm UTC](https://discourse.julialang.org/t/is-it-possible-to-get-an-exception-message-as-a-string/3201/1 "2017-04-13T13:06:58Z")

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So, for language interop reasons, I’d like to translate Julia exceptions into a different kind of error. In the C API, it is pretty clear that `jl_exception_occurred` is what to use to check if an exception occurred or not. But, if an exception has occurred, I haven’t found it clear how to extract the error message from it. Some exceptions seem to have the `msg` field, but others (like `DomainError`) do not.

Is it possible to get the message of an arbitrary exception as a string? For `DomainError` thrown by `sqrt(-1)`, this would be:

```julia
ERROR: DomainError:
sqrt will only return a complex result if called with a complex argument. Try sqrt(complex(x)).
 in sqrt(::Int64) at ./math.jl:211

```

Thanks!

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### Author: ![stevengj](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stevengj/32/71_2.png) [@stevengj](https://discourse.julialang.org/u/stevengj)
#### Post date: [April 13, 2017, 1:58pm UTC](https://discourse.julialang.org/t/is-it-possible-to-get-an-exception-message-as-a-string/3201/2 "2017-04-13T13:58:40Z")

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You can call `sprint(showerror, e)` to get the message of an exception in string form, or `sprint(showerror, e, backtrace())` in the context of a `catch` block to print additional information extracted from the backtrace.

For example, the `sqrt` message you quoted is printed by a special case of `showerror` given a backtrace indicating that the `DomainError` came from a `sqrt` call.

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<div class="post-metadata">

### Author: ![izaid](https://avatars.discourse-cdn.com/v4/letter/i/ee7513/32.png) [@izaid](https://discourse.julialang.org/u/izaid)
#### Post date: [April 13, 2017, 2:05pm UTC](https://discourse.julialang.org/t/is-it-possible-to-get-an-exception-message-as-a-string/3201/3 "2017-04-13T14:05:42Z")

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Thanks, stevengj! However, if I do this:

```julia
try
  sqrt(-1)
catch e
  bt = backtrace()
  msg = sprint(showerror, e, bt)
  println(msg)
end

```

I don’t get the full error message, what I see is:

```julia
DomainError:
 in backtrace() at ./error.jl:26
 in backtrace() at /Applications/Julia-0.5.app/Contents/Resources/julia/lib/julia/sys.dylib:?
 in include_from_node1(::String) at ./loading.jl:488
 in include_from_node1(::String) at /Applications/Julia-0.5.app/Contents/Resources/julia/lib/julia/sys.dylib:?
 in process_options(::Base.JLOptions) at ./client.jl:262
 in _start() at ./client.jl:318
 in _start() at /Applications/Julia-0.5.app/Contents/Resources/julia/lib/julia/sys.dylib:?

```

Is there a way to get the full message?

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<div class="post-metadata">

### Author: ![izaid](https://avatars.discourse-cdn.com/v4/letter/i/ee7513/32.png) [@izaid](https://discourse.julialang.org/u/izaid)
#### Post date: [April 13, 2017, 2:10pm UTC](https://discourse.julialang.org/t/is-it-possible-to-get-an-exception-message-as-a-string/3201/4 "2017-04-13T14:10:28Z")

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Ah, okay, so this does work (sort of, see below) if I use `catch_backtrace()` instead of `backtrace()`. However, if I try and encapsulate the whole thing in a function, it seems to no longer work.

To be clear, this works and gives me the full message:

```julia
try
  sqrt(-1)
catch e
  bt = catch_backtrace()
  msg = sprint(showerror, e, bt)
  println(msg)
end

```

Whereas this does not:

```julia
function test()
  try
    sqrt(-1)
  catch e
    bt = catch_backtrace()
    msg = sprint(showerror, e, bt)
    println(msg)
  end
end

test()

```

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<div class="post-metadata">

### Author: ![Ralph\_Smith](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ralph_smith/32/10344_2.png) [@Ralph\_Smith](https://discourse.julialang.org/u/Ralph_Smith)
#### Post date: [April 14, 2017, 2:37am UTC](https://discourse.julialang.org/t/is-it-possible-to-get-an-exception-message-as-a-string/3201/5 "2017-04-14T02:37:32Z")

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By default Julia inlines most or all of the `sqrt` call when the block is inside a function. Hence the `sqrt` symbol is missing from the backtrace, and `showerr` doesn’t get the hint to add the detailed message. You could turn off inlining if you _really_ want the message.