Setting a time limit for each loop iteration

Question

In R, I am looping over a vector of objects and apply the same commands at each iteration. How to (i) stop an iteration that takes too long, (ii) print a error/warning message and (iii) go ahead with the next iteration?

For instance, let's say that I have a vector containing 3 time periods and I make R sleeps for these periods, applying a time limit of 5 seconds. If a for loop iteration takes more than 5 seconds (second one of the vector here), it should stop at (around) 5 seconds and keeps going.

My problem with the below codes is that, if an iteration takes too long, R does not stop, but only prints the error message once the iteration is finished and not straight at the time limit.

vec <- c(2, 12, 3)

# using base R 'setTimeLimit' function
for(i in 1:length(vec)){
    cat(". Sleeping", vec[i], "seconds\n")

    tryCatch(
        {
            system.time(
                local(
                    {
                        setTimeLimit(elapsed = 5, transient = TRUE)
                        Sys.sleep(vec[i])
                    }
                )
            )
        },
        error=function(e){cat(conditionMessage(e), "\n")}
    )
}

# using R.utils 'withTimeout' function
library(R.utils)
for(i in 1:length(vec)){
    cat(". Sleeping", vec[i], "seconds\n")

    # first 'tryCatch' if error NOT caused by a timeout
    tryCatch(

        # second 'tryCatch' if error caused by a timeout
        tryCatch(
            withTimeout(
                    Sys.sleep(vec[i]),
                    timeout=5,
                    onTimeout="error"
            ),
            TimeoutException = function(ex) cat("Timeout. Skipping.\n")
        ),
        error=function(e){cat(conditionMessage(e), "\n")}
    )
}

EDIT

As mentionned in the comments, this solution does not work neither with my example.

for(i in 1:length(vec)){
+     tryCatch(
+         expr = {
+             withTimeout({Sys.sleep(vec[i]); cat(". Sleeping ", vec[i], " seconds\n")},
+                          timeout = 5)
+             },
+         TimeoutException = function(ex) cat("Timeout. Skipping.\n")
+     )
+ }

It outputs:

. Sleeping  2  seconds
Timeout. Skipping.          # this message shows up after 12 seconds anyway (I am trying to stop it after timeout = 5s here)
. Sleeping  3  seconds

EDIT 2

My example involving the Sys.sleep function does not work with withTimeout.

From R.Utils manual:

(*) Note that on Unix and macOS, Sys.sleep(time) will signal a timeout error only after time seconds passed, regardless of timeout limit (< time).

Taking another example, the SO post mentioned in the comments below actually works.

library(R.utils)

vec <- c(1e+02, 1e+06, 1e+04)

# the second element of the vector takes some time to run
foo <- function(i){
            for(j in 1:i){
                invisible(capture.output(print(j)))
            }
    }

# checking that the second element will take a long time (15 seconds)
system.time(foo(vec[1]))
#  user  system elapsed
# 0.002   0.001   0.001

system.time(foo(vec[2]))
#   user  system elapsed
# 11.557   3.157  15.543

system.time(foo(vec[3]))
#  user  system elapsed
# 0.109   0.031   0.148

for(k in vec){
    tryCatch(
        {
            system.time(withTimeout(
                {cat("... Processing ", k, " times...\n\n"); invisible(capture.output(foo(k)))},
                timeout = 5
            ))
        }, 
        TimeoutException = function(ex) cat("Timeout. Skipping.\n\n")
    )
}

#... Processing  100  times...
#
#... Processing  1e+06  times...
#
#Timing stopped at: 4.993 0.029 5.022     # it stops at timeout = 5s
#Timeout. Skipping.
#
#... Processing  10000  times...