How To Run A Command In Ubuntu?

Unix: How exactly does the time command work? And why a program could fail (only) when launched with it?

• I am launching a benchmark (DaCapo java benchmarks) with the time command prepended on a Unix platform (Ubuntu). The same command does not fail when launched without a time command but it randomly fails (80% of the times) when time is invoked. Parameters are passed correctly and in the cases where the program terminates its execution the results are just equal to the results obtained without using time. What can time do to prevent the program from completing its run? Edit: I am trying to profile lusearch, a benchmark of the http://dacapobench.org/. I want to launch it with different configurations (number of threads and number of iterations), disregard the benchmark output and use time to record real, user and system time. With the vast majority of the configurations, my script works just fine, launches the benchmark and records the time. With one particular configuration (large dataset, two threads and ten iterations) the benchmark sometimes does not reach termination (80% of the cases, out of almost 100 tentatives). This is the command I am using to launch it: (time -p java -jar DaCapo.jar lusearch -s large -t 2 -i 10   >/dev/null 2>/dev/null) 2>&1 | awk '{print $2 $4 $6}' > timed & However, if I don't prepend time the benchmark just terminates 100% of the times (in about 100 tentatives as well): (java -jar DaCapo.jar lusearch -s large -t 2 -i 10 >/dev/null 2>/dev/null) This behavior happens only with this benchmark - and with this configuration -, while if profile some other benchmark or use a different number number of threads or a different number of iterations I don't see the same thing happening. My guess would be that it has to do with something that time is doing that interferes with the benchmark. I don't see how a fork+exec (which is what I was expecting from time) could change the benchmark behavior. Also, I am using the builtin bash time command and, following a friend suggestion, I posted the question on stackoverflow as well: http://stackoverflow.com/questions/13859491/can-unix-time-command-interfere-with-the-running-program

• Answer:

  Short answer:  read the source code to find out. http://ftp.debian.org/debian/pool/main/t/time/ Or, maybe strace it to see what it's doing. Longer answer: Time parses it's "command line arguments" and constructs another commandline that it uses to run a child process. The command you're running is doing something unexpected.    Time's expecting the child process to play by the standard set of UNIX rules regarding how it executes and exits - and you're doing something slightly different.  I can't really guess what it might be.  Thus, we're back at the short answer.