Implement "attach" command and graceful exiting

[yarikoptic]

The target is to implement (mecha)babs support for monitoring entire subject processing job script, so we could do smth like (expressing)

diff --git a/code/participant_job.sh b/code/participant_job.sh
index a49142d..c071ce2 100755
--- a/code/participant_job.sh
+++ b/code/participant_job.sh
@@ -6,6 +6,9 @@
 
 #SBATCH --time=24:00:00
 
+DUCT_PREFIX="logs/duct_${subid}_" con-duct attach &
+duct_pid=$!
+
 # shellcheck disable=SC1091
 source /dartfs/rc/lab/D/DBIC/DBIC/CON/asmacdo/mechababs/.venv/bin/activate
 
@@ -109,7 +112,6 @@ if [ ! -L "${CONTAINER_JOB}" ]; then
   exit 1
 fi
 
-export DUCT_PREFIX="logs/duct_${subid}_"
 
 # Step 1: Run BIDS app via containers-run
 datalad containers-run \
@@ -156,4 +158,7 @@ echo '# Push the branch with provenance records:'
 # shellcheck disable=SC2154
 flock "${DSLOCKFILE}" git push outputstore "${BRANCH}"
 
-echo SUCCESS
\ No newline at end of file
+
+kill "$duct_pid"  # inform to gracefully exit
+
+echo SUCCESS

docstring for attach would tell user to use kill potentially with specific signal (9 or INT) as to e.g. trigger killing without graceful shutdown which should happen on default kill which is TERM (15).

and attach will just monitor current session (like we have run --session=current) and not require a command to run

[yarikoptic]

while talking to @CodyCBakerPhD I now started to worry -- will processes within (singuarity) container be under the same session id?