CODEWITHSUNDEEP
rjulia
Yihui Xie
Yihui Xie

Reputation: 30184

is there a way to capture stdout in Julia like capture.output() in R?

In R, capture.output() can capture the output to stdout in an expression as a character vector, e.g.

> x = capture.output(print(1:10))
> x
[1] " [1]  1  2  3  4  5  6  7  8  9 10"

Is there an equivalent function in Julia?

Upvotes: 11

Views: 2834

Answers (3)

Steven G. Johnson
Steven G. Johnson

Reputation: 441

With Julia 0.2, there is now a way to capture standard output: you can call redirect_stdout to convert STDOUT into a pipe that you can read from.

This is mainly useful to capture output from external C libraries. As Stefan mentioned, most Julia I/O functions accept an io argument that allows you to print to an arbitrary destination, such as a string buffer.

Upvotes: 7

jverzani
jverzani

Reputation: 5700

Not sure what you are after, but if you are trying to bring knitr to julia then awesome!

The Gadfly package has weave, which does some of this.

Check out https://github.com/dcjones/Gadfly.jl/blob/master/src/weave.jl#L19

and

https://github.com/dcjones/Gadfly.jl/blob/master/src/weave.jl#L423

I've been using it in https://github.com/jverzani/Weave.jl to make self-grading quizzes from markdown.

Upvotes: 3

StefanKarpinski
StefanKarpinski

Reputation: 33290

Standard library functions should all accept an optional IO-typed first argument that will be printed to if provided but otherwise will default to STDOUT. In that case, you can use sprint(io->f(io,...)) to capture what's printed to a string. If the functions haven't been written to print to a given IO object, then there isn't a way to redirect the output.

Upvotes: 4

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