ggsave creates superflous, misnamed additional directory when saving to a directory containing a % character

[stephan-hutter]

Tested on Windows 11 and Amazon Linux 2023

When saving a plot to a directory containing a % character via ggsave one has to use %% in order for the character to be read as a single %.

However, when you do this ggsave will prompt that it cannot find the directory and ask to create a directory (or automatically create the directory if create.dir = TRUE).

It will then proceed to create a directory where all %% are interpreted literally as two % characters, but continue to store the file in the original requested directory, leaving the newly created directory empty.

Obviously, this second directory should never be created.

Reprex:

dir.create("a%b")
ggplot2::ggsave("a%%b/test.png", 
                ggplot2::ggplot(cars) + ggplot2::geom_bar(ggplot2::aes(x = speed)), 
                create.dir = TRUE)
#> ✔ Created directory: 'a%%b'.
#> Saving 7 x 5 in image

[teunbrand]

Hmm, frustrating.
I think it might have to do with the devices interpreting anything remotely like sprintf formatting.
Just to show that this happens outside ggplot2 as well.

file <- "a%%b/test.png"
dir.create("a%b")

file.exists(file)
#> [1] FALSE

png(file)
plot(1:10)
dev.off()
#> png 
#>   2

file.exists(file)
#> [1] FALSE
file.exists("a%b/test.png")
#> [1] TRUE

^{Created on 2026-04-27 with reprex v2.1.1}

This allows one to do Plot%03.png or dir%03/plot.png to automatically increment integers at %03d for different plots.
However, it is giving an incorrect path to dir.create().

I don't know what the right solution would be. I think create.dir should mirror what the graphics devices do, but we'd have to dig a little bit how exactly devices are handling the formatting.