How to make g++ to show the execution time in terminal?

Question

I want to make g++ showing me what is the execution time and maybe the return too.

g++ file.cpp -o file
./file

When i make the executable file and then call in it is showing only the output without the return and execution time.

And i want to make it showing something like this:

Process returned 0 (0x0)    execution time : 0.002 s

Thank you for the attention!

Instead say `time ./file` and parse the output as per your needs. — devnull, Mar 02 '14 at 20:56
The shell captures the exit status in the `$?` variable, so `echo $?` shows you the exit status of the most recently executed command. But I don't know how to do it on the Windows command prompt. — Brian Bi, Mar 02 '14 at 20:58

benedek · Accepted Answer · 2014-03-02T21:08:12.127

You can measure how long your process takes with the "time" command.

To determine the return value, you can print the value of the $? environment variable after running your program:

time ./file ; echo Process returned $?

You can also specify how exactly time should format its results with the -f (or --format) option. However, some Linux distributions might use a bash-builtin time implementation by default which lacks that option, so you might have to give the full path to use the real time program:

/usr/bin/time -f "Execution time: %E" ./file

score 8 · Answer 2 · answered Mar 02 '14 at 20:56

8

You can use time command as follows:
time ./file

answered Mar 02 '14 at 20:56

Shashwat Kumar

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score 3 · Answer 3 · edited May 23 '17 at 12:01

3

Look here first: calculating execution time in c++

You can also use a clock (from time.h)in code (although for multi-threaded code it works kinda funny)

int a;
unsigned t0 = clock(), t1;
std::cin >> a;
t1 = clock() - t0;

edited May 23 '17 at 12:01

Community

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answered Mar 02 '14 at 20:57

turnt

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score 0 · Answer 4 · edited May 23 '17 at 12:09

Read carefully time(7). You may use time(1) externally (from your shell, like answered here). You could also use from inside your program syscalls like clock_gettime(1) etc...

Don't expect timing to be really meaningful or accurate for small delays (e.g. less than half a second).

BTW, your question has not much to do with the GCC compiler (i.e. g++). If using a recent GCC 4.8 with -std=c++11 you could use std::chrono etc etc... And even if using these it is not the compiler which is timing your program (but some library functions using syscalls)

How to make g++ to show the execution time in terminal?

4 Answers4