time.1

<B>Digital的Unix操作系统VAX 4.2源码</B>

.\" SCCSID: @(#)time.1	8.3	3/28/91
.TH time 1 
.SH Name
time \- time a command
.SH Syntax
.B time
.I command
.br
.B /bin/time
.I command
.SH Description
.NXR "time command"
.NXR "command" "timing"
The
.PN time
command lets the specified command execute and then outputs the amount
of elapsed real time, the time spent in the operating system, and the
time spent in execution of the command.  Times are reported in seconds
and are written to standard error.
.PP
If you are using any shell except the C shell,
.MS csh 1 ,
you can give the
.PN time
command as shown on the first line of the Syntax section.  If you are
using the C shell, you must use the
.PN time
command's full pathname as shown on the second line of the Syntax
section.  If you do not use the full pathname,
.PN csh
will execute its own built-in
.PN time
command that supplies additional information and uses a different
output format.
.PP
The 
.PN time
command can be used to cause a command to be timed no matter how much 
CPU time it takes.  For example:
.EX
% /bin/time cp /etc/rc /usr/bill/rc
        0.1 real         0.0 user         0.0 sys
% /bin/time nroff sample1 > sample1.nroff
        3.6 real         2.4 user         1.2 sys
.EE
This example indicates that the 
.PN cp
command used negligible amounts of user
.Pn ( user )
and system time
.Pn ( sys ),
and had an elapsed time
.Pn ( real )
of 1/10 second (0.1).  The
.PN nroff
command used 2.4 seconds of user time and 1.2 seconds of system time,
and required 3.6 seconds of elapsed time.
.SH Restrictions
Times are measured to an accuracy of 1/10 second.  Thus, the sum of the
user and system times can be larger than the elapsed time.
.SH See Also
csh(1)