Executing unix commands in C++

Question

Is there a way to use the unix 'time' command in C++ and store each of its outputs in a variable?

EDIT: If there isn't a way, then what about calling time in a bash script and storing the returned values some way?

Thank you!

Is there a particular reason that you don't want to use the time function, and the various functions that format time_t variables? E.g. stackoverflow.com/questions/2242963/…. — dsolimano
– dsolimano, Commented Feb 26, 2012 at 4:46
Yes, I tried a few such functions - I had a problem to compile clock_gettime, and all the other time functions I tried that did compile had other problems. time() for example gave me diff in integer, others gave me diff in double but it was the CPU time and not clock time (the 'real' in the unix time command). — user247866
– user247866, Commented Feb 26, 2012 at 4:49

Potatoswatter · Accepted Answer · 2012-02-26 05:06:45Z

1

Supposing you are on UNIX, then the C++ standard std::system function will behave as defined in POSIX, that is, execute a command as with sh. Before doing this, you can connect your own stdin and stdout to a local pipe by first using dup to create aliases of STDIN_FILENO and STDOUT_FILENO, then close the aforementioned file descriptors, then pipe to open a pipe on the newly freed descriptors.

Then you can interact with std::cin and std::cout. Well, it would be a good idea to flush the C++ interface before beginning.

This isn't all really a good idea, though. It should be simpler to use the POSIX C interface to get the relevant data directly.

answered Feb 26, 2012 at 5:06

Potatoswatter

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user247866 Over a year ago

As you mention, I'm looking for a simpler solution. But it's good to know, thanks!

knk · Accepted Answer · 2012-02-26 05:16:48Z

1

If you are ok with using Boost libraries, then this should do it http://www.boost.org/doc/libs/1_49_0/doc/html/date_time/examples.html#date_time.examples.seconds_since_epoch

the good part is it also handles time zones conversions :)

answered Feb 26, 2012 at 5:16

knk

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Carl Norum · Accepted Answer · 2012-02-26 05:07:17Z

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You can use system(3) or popen(3), but there's almost always a better, more portable, and native solution, depending on what exactly you're looking for. In your specific case it seems like what you're really looking for a combination of getrusage(2) and ftime(3).

edited Feb 26, 2012 at 5:07

answered Feb 26, 2012 at 5:01

Carl Norum

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