Example uses of the command "time"

A Brief Introduction

Illustration of a command line in Linux

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If you want to see how much CPU time the command "head -n 10000 largefile.txt" takes, you can use:

time head -n 10000 largefile.txt

real 0m4.866s

user 0m0.001s

sys 0m0.021s

In order to access the GNU version of the time command you may have to specify the whole path, such as /usr/bin/time. This version provides more functionality, such as memory and I/O statistics. For example:

/usr/bin/time -f "\n%E elapsed,\n%U user,\n%S system,\n%M memory\n%x status" head -n 10000 largefile.txt

0:07.96 elapsed,

0.00 user,

0.01 system,

1 memory

0 status

For more options and the units of the various measures see the time man page.