linux - Separately redirecting and recombining stderr/stdout without losing ordering -


i want execute command , want redirect stderr , stdout below:

stderr , stdout -> should written logs.log file while keeping order

stderr -> should printed screen , written errors.log

so far can redirect them both screen , file log.txt this:

command 2>&1 | tee logs.log

but above not need.

to make more clear again results needs be.

after command executed need see on screen result of stderr, need have 1 file named errors.log stderr, , need have file named logs.log result of both stdout , stderr in original order in created.

preserving perfect order while performing separate redirections not theoretically possible without ugly hackery. ordering preserved in writes (in o_append mode) directly same file; put tee in 1 process not other, ordering guarantees go out window , can't retrieved without keeping information syscalls invoked in order.

so, hackery like? might this:

# eat our initialization time *before* start background process sudo sysdig-probe-loader  # now, start monitoring syscalls made children of shell write fd 1 or 2 # ...funnel content our logs.log file sudo sysdig -s 32768 -b -p '%evt.buffer' \   "proc.apid=$$ , event.type=write , (fd.num=1 or fd.num=2)" \   > >(base64 -i -d >logs.log) \   & sysdig_pid=$!  # run your-program, stderr going both console , errors.log ./your-program >/dev/null 2> >(tee errors.log)

that said, remains ugly hackery: catches writes direct fds 1 , 2, , doesn't track further redirections may take place. (this improved performing writes fifos, , using sysdig track writes fifos; way fdup() , similar operations work as-expected; above suffices prove concept).

obviously, shouldn't of this. update program support whatever logging infrastructure available in native language (log4j in java, python logging module, etc) allow logging configured explicitly.


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