4.3.2. How long does it take?

Bash offers a built-in time command that displays how long a command takes to execute. The timing is highly accurate and can be used on any command. In the example below, it takes about a minute and a half to make this book:

tilly:~/xml/src> time make
Output written on abook.pdf (222 pages, 1619861 bytes).
Transcript written on abook.log.

real    1m41.056s
user    1m31.190s
sys     0m1.880s

The GNU time command in /usr/bin (as opposed to the shell built-in version) displays more information that can be formatted in different ways. It also shows the exit status of the command, and the total elapsed time. The same command as the above using the independent time gives this output:

tilly:~/xml/src> /usr/bin/time make
Output written on abook.pdf (222 pages, 1595027 bytes).
Transcript written on abook.log.

Command exited with non-zero status 2
88.87user 1.74system 1:36.21elapsed 94%CPU 
                                (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (2192major+30002minor)pagefaults 0swaps

Refer again to the Info pages for all the information.