# Is it possible to suppress the chain of 'caused by' output when handling an exception?
**URL:** https://discourse.julialang.org/t/is-it-possible-to-suppress-the-chain-of-caused-by-output-when-handling-an-exception/107823
**Category:** General Usage
**Tags:** exception
**Created:** [December 19, 2023, 4:35pm UTC](https://discourse.julialang.org/t/is-it-possible-to-suppress-the-chain-of-caused-by-output-when-handling-an-exception/107823 "2023-12-19T16:35:57Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@johnomotani](https://discourse.julialang.org/u/johnomotani)
#### Post date: [December 19, 2023, 4:35pm UTC](https://discourse.julialang.org/t/is-it-possible-to-suppress-the-chain-of-caused-by-output-when-handling-an-exception/107823/1 "2023-12-19T16:35:57Z")
When handling an exception that was ‘caused by’ another exception, Julia prints out a stack of exceptions. Normally this is helpful, but in this case I want to handle the exception, and give the user a helpful message. I can do this, but after my error message is printed, there is the original exception which (in this case) makes it harder for the user to find the message I want them to see.
For example
```julia
julia> function foo()
try
Base.require(Main, :NCDatasets)
catch
error("To handle this error, do X")
end
end
foo (generic function with 1 method)
julia> foo()
ERROR: To handle this error, do X
Stacktrace:
[1] error(s::String)
@ Base ./error.jl:35
[2] foo()
@ Main ./REPL[11]:5
[3] top-level scope
@ REPL[12]:1
caused by: ArgumentError: Package NCDatasets not found in current path, maybe you meant `import/using .NCDatasets`.
- Otherwise, run `import Pkg; Pkg.add("NCDatasets")` to install the NCDatasets package.
Stacktrace:
[1] macro expansion
@ ./loading.jl:1630 [inlined]
[2] macro expansion
@ ./lock.jl:267 [inlined]
[3] require(into::Module, mod::Symbol)
@ Base ./loading.jl:1611
[4] foo()
@ Main ./REPL[11]:3
[5] top-level scope
@ REPL[12]:1
```
How can I get rid of the `caused by: ArgumentError` block (which in my actual use case has a long stack trace which pushes my error message off the top of the screen)?
PS I do want to raise an error that stops execution (but does not exit Julia) from far down a call stack, so I do not want (for example) to just print a message and return from the function.
---
### Author:  [@mkitti](https://discourse.julialang.org/u/mkitti)
#### Post date: [December 19, 2023, 5:01pm UTC](https://discourse.julialang.org/t/is-it-possible-to-suppress-the-chain-of-caused-by-output-when-handling-an-exception/107823/2 "2023-12-19T17:01:05Z")
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>
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Edit: I thought you were asking a different question. One second …
---
### Author:  [@gdalle](https://discourse.julialang.org/u/gdalle)
#### Post date: [December 19, 2023, 5:16pm UTC](https://discourse.julialang.org/t/is-it-possible-to-suppress-the-chain-of-caused-by-output-when-handling-an-exception/107823/3 "2023-12-19T17:16:40Z")
Is this related to the difference between `throw` and `rethrow`? I’m a little bit unclear on that myself
---
### Author:  [@mbauman](https://discourse.julialang.org/u/mbauman)
#### Post date: [December 19, 2023, 5:20pm UTC](https://discourse.julialang.org/t/is-it-possible-to-suppress-the-chain-of-caused-by-output-when-handling-an-exception/107823/4 "2023-12-19T17:20:27Z")
Yes, `rethrow` is one option here. But: the docs admonish you about _not_ using it because it “lies” about what caused the problem 🙂
> The alternative form `rethrow(e)` allows you to associate an alternative exception object `e` with the current backtrace. However this misrepresents the program state at the time of the error so you’re encouraged to instead throw a new exception using `throw(e)`.
```julia-repl
julia> function foo()
try
Base.require(Main, :NCDatasets)
catch ex
rethrow(ArgumentError("To handle this error, do X"))
end
end
foo (generic function with 1 method)
julia> foo()
ERROR: ArgumentError: To handle this error, do X
Stacktrace:
[1] macro expansion
@ ./loading.jl:1630 [inlined]
[2] macro expansion
@ ./lock.jl:267 [inlined]
[3] require(into::Module, mod::Symbol)
@ Base ./loading.jl:1611
[4] foo()
@ Main ./REPL[17]:3
[5] top-level scope
@ REPL[18]:1
```
^^ This stack trace points at `require`, not the catch block of `foo()`!