`file_copy` with `overwrite = TRUE` permission problem

[tentacles-from-outer-space]

I ran into strange behavior with file_copy.

When another user with the same group create file (with rw-rw-rw- permissions) then

library(fs)

file_info("tmp-tst-copy.txt")$permissions # rw-rw-rw-
file_access("tmp-tst-copy.txt", "write") # TRUE

file_copy("tmp-tst-origin.txt", "tmp-tst-copy.txt", overwrite = TRUE)
Error: [EPERM] Failed to copy 'tmp-tst-origin.txt' to 'tmp-tst-copy.txt': operation not permitted

But actually file is removed (so runing command second time works as the destination file does not exists).

There is no problem with file_delete("tmp-tst-copy.txt").
There is no problem with system command cp tmp-tst-origin.txt tmp-tst-copy.txt

Session Info

> sessioninfo::session_info()
─ Session info ────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
 setting  value
 version  R version 4.5.0 (2025-04-11)
 os       Red Hat Enterprise Linux 8.10 (Ootpa)
 system   x86_64, linux-gnu
 ui       RStudio
 language (EN)
 collate  en_US.UTF-8
 ctype    en_US.UTF-8
 tz       Europe/Warsaw
 date     2025-12-02
 rstudio  2025.05.0+496.pro5 Mariposa Orchid (server)
 pandoc   NA
 quarto   1.6.42 @ /usr/lib/rstudio-server/bin/quarto/bin/quarto

─ Packages ─────────────────────────────────────────────
 package     * version date (UTC) lib source
 cli           3.6.5   2025-04-23 [1] RSPM (R 4.5.0)
 crayon        1.5.3   2024-06-20 [1] RSPM (R 4.5.0)
 fs          * 1.6.6   2025-04-12 [1] RSPM (R 4.5.0)
 glue          1.8.0   2024-09-30 [1] RSPM (R 4.5.0)
 lifecycle     1.0.4   2023-11-07 [1] RSPM (R 4.5.0)
 magrittr      2.0.3   2022-03-30 [1] RSPM (R 4.5.0)
 pillar        1.10.2  2025-04-05 [1] RSPM (R 4.5.0)
 pkgconfig     2.0.3   2019-09-22 [1] RSPM (R 4.5.0)
 pkgload       1.4.0   2024-06-28 [1] RSPM (R 4.5.0)
 rlang         1.1.6   2025-04-11 [1] RSPM (R 4.5.0)
 rstudioapi    0.17.1  2024-10-22 [1] RSPM (R 4.5.0)
 sessioninfo   1.2.3   2025-02-05 [1] RSPM (R 4.5.0)
 tibble        3.2.1   2023-03-20 [1] RSPM (R 4.5.0)
 utf8          1.2.5   2025-05-01 [1] RSPM (R 4.5.0)
 vctrs         0.6.5   2023-12-01 [1] RSPM (R 4.5.0)

 [1] /opt/R/libraries/4.5.0_2025-05
 [2] /opt/R/4.5.0/lib/R/library
 * ── Packages attached to the search path.

───────────────────────────────────────────────────

[jeroen]

I wonder if this is still a problem with newer libuv. Could you try to make a reproducer in a Dockerfile?

[tentacles-from-outer-space]

FROM rocker/r-base:latest

WORKDIR /fs-test

# Create group and users
RUN groupadd test-users && \
    useradd -m -G test-users userA && \
    useradd -m -G test-users userB

RUN apt-get update && apt-get install -y libuv1-dev
RUN R --slave -e 'install.packages("fs", repos="http://cran.r-project.org")'

USER root
RUN chown -R root:test-users /fs-test/
RUN chmod -R g+rw /fs-test

COPY ./fs.R /fs-test/fs.R

# userB creates his file
USER userB
RUN touch fileB.txt && chmod 660 fileB.txt && chgrp test-users fileB.txt 

# Switch to userA for script execution
USER userA
# CMD ["bash", "-c", "Rscript fs.R > fs-out.log.txt && cat fs-out.log.txt"]
CMD ["bash", "-c", "R -f fs.R > fs-out.log.txt 2>&1 && cat fs-out.log.txt"]

fs.R:

library(fs)
packageVersion("fs")

file.create("fileA.txt")
file_exists("fileB.txt")
file_info("fileB.txt")[1:7]

try(
    file_copy("fileA.txt", "fileB.txt", overwrite = TRUE) # fail
)

file_exists("fileB.txt")
file_copy("fileA.txt", "fileB.txt", overwrite = TRUE)
file_exists("fileB.txt")

Running

docker build -t r-fs-tests -f r-fs-tests
docker run r-fs-tests

gives

Emulate Docker CLI using podman. Create /etc/containers/nodocker to quiet msg.

R version 4.5.3 (2026-03-11) -- "Reassured Reassurer"
Copyright (C) 2026 The R Foundation for Statistical Computing
Platform: x86_64-pc-linux-gnu

R is free software and comes with ABSOLUTELY NO WARRANTY.
You are welcome to redistribute it under certain conditions.
Type 'license()' or 'licence()' for distribution details.

  Natural language support but running in an English locale

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Type 'contributors()' for more information and
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Type 'demo()' for some demos, 'help()' for on-line help, or
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> library(fs)
> packageVersion("fs")
[1] ‘2.0.1’
> 
> file.create("fileA.txt")
[1] TRUE
> file_exists("fileB.txt")
fileB.txt 
     TRUE 
> file_info("fileB.txt")[1:7]
       path type size permissions   modification_time  user      group
1 fileB.txt file    0   rw-rw---- 2026-03-28 18:40:17 userB test-users
> 
> try(
+     file_copy("fileA.txt", "fileB.txt", overwrite = TRUE) # fail
+ )
Error : [EPERM] Failed to copy 'fileA.txt' to 'fileB.txt': operation not permitted
> 
> file_exists("fileB.txt")
fileB.txt 
    FALSE 
> file_copy("fileA.txt", "fileB.txt", overwrite = TRUE)
> file_exists("fileB.txt")
fileB.txt 
     TRUE 
>