ps_create_time() and ps_boot_time() drifts on Linux

[dansmith01]

I noticed that ps_create_time() will return a different process creation time, depending on the creation time of the process that queries it.

First Process:

docker run -it --rm --name test rocker/r-ver:4.5.0
install.packages('ps')
Sys.getpid()
#> [1] 1
ps::ps_create_time(ps::ps_handle(1))
#> [1] "2025-05-07 17:50:18 GMT"

(wait a few minutes before launching second process)

Second Process:

docker exec -it test R
ps::ps_create_time(ps::ps_handle(1))
#> [1] "2025-05-07 17:50:35 GMT"

(wait a few more minutes)

Third Process:

docker exec -it test R
ps::ps_create_time(ps::ps_handle(1))
#> [1] "2025-05-07 17:51:00 GMT"

[dansmith01]

Looks like the btime field in /proc/stat isn't static.

[dansmith01]

ps_boot_time() shows the issue a little clearer.

First Process:

docker run -it --rm --name test rocker/r-ver:4.5.0
install.packages('ps')
ps::ps_boot_time()
#> [1] "2025-05-07 17:37:16 GMT"

(wait a few minutes before launching second process)

Second Process:

docker exec -it test R
ps::ps_boot_time()
#> [1] "2025-05-07 17:37:26 GMT"

[dansmith01]

ps_boot_time() also drifts on Windows.