Hi, I was creating some exercises for my students when I noticed very strange behavior of the time built-in when sending SIGSTOP to a timed command interactively (via ^Z):
$ time sleep 5 ^Z [1]+ Stopped sleep 5 real 0m0.880s user 0m0.002s sys 0m0.000s $ ps Tf PID TTY STAT TIME COMMAND 31049 pts/21 Ss 0:00 bash 30828 pts/21 T 0:00 \_ sleep 5 30829 pts/21 R+ 0:00 \_ ps Tf $ As you can see, the time command prints the statistics when the signal is received instead of when the sleep command actually finishes. The same happens if I send SIGSTOP with kill(1) to the sleep process. However, other signals seem to work fine (tested with a C program with an empty SIGINT handler), i.e. the signal is correctly received by the command and time waits until the command actually finishes. The actual (/usr/bin/)time binary on my system handles ^Z correctly: $ env time sleep 5 ^Z [1]+ Stopped env time sleep 5 $ fg env time sleep 5 0.00user 0.00system 0:05.00elapsed 0%CPU (0avgtext+0avgdata 676maxresident)k 0inputs+0outputs (0major+215minor)pagefaults 0swaps $ When I do the same with a process running in the background it also works correctly (I presume because it starts a subshell that does the signal handling?): $ time sleep 10 & [1] 31115 $ kill -SIGSTOP %1 [1]+ Stopped time sleep 10 $ kill -SIGCONT %1 $ real 0m10.002s user 0m0.000s sys 0m0.002s [1]+ Done time sleep 10 $ The problem was also reported a long time ago against Debian's bash: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=399076 But I could not find any other references so I guess it has never reached an upstream bug tracker/ml. I have briefly looked at the code... but there are way too much recursions in execute_pipeline() and signal handling all over the place that I'd rather not touch it yet. :) However, if you'd give me some pointers I can look into it. KR -- Dipl.-Ing. Stefan Tauner Research and Development Embedded Systems Department University of Applied Sciences Technikum Wien Hoechstaedtplatz 6, 1200 Vienna, Austria T: +43 1 333 40 77-316 E: stefan.tau...@technikum-wien.at I: embsys.technikum-wien.at I: www.technikum-wien.at
