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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.
tilly:~/xml/src> time make
Output written on abook.pdf (222 pages, 1619861 bytes). Transcript written on abook.log.
real user
sys
1m41.056s
1m31.190s
0m1.880s
real user
sys
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
tilly:~/xml/src> /usr/bin/time make
Output written on abook.pdf (222 pages, 1595027 bytes). Transcript written on abook.log.