On Linux does the remove command rm run in the background

Question

I am trying to run my test cases which are nearly 40k with below scripts.

Just showing some part of script -

#!/bin/bash
# RUN script



echo "please run with: nice nohup ./run_script"

# working directory where script is stored
WORKING_DIR=$(pwd)

# temp directory to build and run the cmake ctest
BUILD_DIR=${BUILD_DIR:-/localtemp/build}

# clean and make build directory
rm -rf $BUILD_DIR
mkdir -p $BUILD_DIR
mkdir -p $BUILD_DIR/../result

cmake -G Ninja

ninja test

Note: I am using parallel threading with 6 cores to run my test cases .

In first attempt all are passing which is true as I fixed all the bugs in my test cases.

But some time If I want to re-run same script freshly, then I am getting the error in running some test cases out of 40k. But If I run that failing test cases separately(one by one) then they are passing perfectly.

So I assumed that rm -rf is taking some time to delete that old binary and symbols of all cases (40 GB files). so I need to wait for complete deletion and then run my script once again . So should I add some delay after rm -rf command in my script .

I read somewhere that rm -rf will return the status once it finishes the work .Then only next command executes. But my scnerio looks like showing that rm -rf is running in background.
Means I should not start new run immediately when I stopped the earlier run . I need to give some time to delete the old output from earlier run using rm -rf command in script (delay introduction) and run my below ninja command after that. Is that true?

Answer 1

It's a little more complicated than that, to be sure. The command rm will not run in the background. What is certain is that the deletion is carried out logically (i.e., objects are removed from the user's perspective); this means that on some operating systems, the low-level deletion may be carried out in the kernel even if the command has finished (the kernel then really clean some internal structures behind your back). However, this should not generally cause any issues with your script. Your issue is mostly certainly elsewhere.

It's possible that some processes keep files even if they appear to be erased... As a result, the disc may not be freed as expected. You'll have to wait for those processes to finish before the kernel cleans the files properly.