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.\"     @(#)time.1	8.1 (Berkeley) 6/6/93
.\"
.Dd April 5, 2021
.Dt TIME 1
.Os
.Sh NAME
.Nm time
.Nd time command execution
.Sh SYNOPSIS
.Nm
.Op Fl clpt
.Op Fl f Ar fmt
.Ar command
.Op Ar argument ...
.Sh DESCRIPTION
The
.Nm
utility
executes and
times
.Ar command .
After the command finishes,
.Nm
writes the total elapsed time (wall clock time),
.Pq Dq real ,
the CPU time spent executing
.Ar command
at user level
.Pq Dq user ,
and the CPU time spent executing in the operating system kernel
.Pq Dq sys ,
to the standard error stream.
Times are reported in seconds.
.Pp
Available options:
.Bl -tag -width Ds
.It Fl c
Displays information in the format used by default the
.Nm
builtin of
.Xr csh 1
uses (%Uu %Ss %E %P %X+%Dk %I+%Oio %Fpf+%Ww).
.It Fl f
Specify a time format using the
.Xr csh 1
.Nm
builtin syntax.
The following sequences may be used in the format string:
.Pp
.Bl -tag -width 4n -compact
.It \&%U
The time the process spent in user mode in cpu seconds.
.It \&%S
The time the process spent in kernel mode in cpu seconds.
.It \&%E
The elapsed (wall clock) time in seconds.
.It \&%P
The CPU percentage computed as (%U + %S) / %E.
.It \&%W
Number of times the process was swapped.
.It \&%X
The average amount in (shared) text space used in Kbytes.
.It \&%D
The average amount in (unshared) data/stack space used in Kbytes.
.It \&%K
The total space used (%X + %D) in Kbytes.
.It \&%M
The maximum memory the process had in use at any time in Kbytes.
.It \&%F
The number of major page faults (page needed to be brought from disk).
.It \&%R
The number of minor page faults.
.It \&%I
The number of input operations.
.It \&%O
The number of output operations.
.It \&%r
The number of socket messages received.
.It \&%s
The number of socket messages sent.
.It \&%k
The number of signals received.
.It \&%w
The number of voluntary context switches (waits).
.It \&%c
The number of involuntary context switches.
.El
.It Fl l
Lists resource utilization information.
The contents of the
.Ar command
process's
.Em rusage
structure are printed; see below.
.It Fl p
The output is formatted as specified by
.St -p1003.2-92 .
.It Fl t
Displays information in the format used by default the
.Nm
builtin of
.Xr tcsh 1
uses (%Uu %Ss %E %P\\t%X+%Dk %I+%Oio %Fpf+%Ww) with
three decimal places for time values.
.El
.Pp
Some shells, such as
.Xr csh 1
and
.Xr ksh 1 ,
have their own and syntactically different built-in version of
.Nm .
The utility described here
is available as
.Pa /usr/bin/time
to users of these shells.
.Ss Resource Utilization
If the
.Fl l
option is given, the following resource usage
information is displayed
in addition to the timing information:
.Bl -item -offset indent -compact
.It
maximum resident set size
.It
average shared memory size
.It
average unshared data size
.It
average unshared stack size
.It
page reclaims
.It
page faults
.It
swaps
.It
block input operations
.It
block output operations
.It
messages sent
.It
messages received
.It
signals received
.It
voluntary context switches
.It
involuntary context switches
.El
Resource usage is the total for the execution of
.Ar command
and any child processes it spawns, as per
.Xr wait4 2 .
.Sh FILES
.Bl -tag -width Xsys/resource.hX -compact
.It Aq sys/resource.h
.El
.Sh EXIT STATUS
The
.Nm
utility exits with one of the following values:
.Bl -tag -width indent
.It 1-125
An error occurred in the
.Nm
utility.
.It 126
The
.Ar command
was found but could not be invoked.
.It 127
The
.Ar command
could not be found.
.El
.Pp
Otherwise, the exit status of
.Nm
will be that of
.Ar command .
.Sh SEE ALSO
.Xr csh 1 ,
.Xr ksh 1 ,
.Xr clock_gettime 2 ,
.Xr getrusage 2 ,
.Xr wait4 2
.Sh STANDARDS
The
.Nm
utility conforms to
.St -p1003.2-92 .
.Sh BUGS
The granularity of seconds on microprocessors is crude and
can result in times being reported for CPU usage which are too large by
a second.