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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),

q Dq real ,
the CPU time spent executing
.Ar command
at user level

q Dq user ,
and the CPU time spent executing in the operating system kernel

q Dq sys ,
to the standard error stream.
Times are reported in seconds.

p
Available options:
l -tag -width Ds t 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).
t Fl f Specify a time format using the
.Xr csh 1
.Nm
builtin syntax.
The following sequences may be used in the format string:

p
l -tag -width 4n -compact t %U The time the process spent in user mode in cpu seconds.
t %S The time the process spent in kernel mode in cpu seconds.
t %E The elapsed (wall clock) time in seconds.
t %P The CPU percentage computed as (%U + %S) / %E.
t %W Number of times the process was swapped.
t %X The average amount in (shared) text space used in Kbytes.
t %D The average amount in (unshared) data/stack space used in Kbytes.
t %K The total space used (%X + %D) in Kbytes.
t %M The maximum memory the process had in use at any time in Kbytes.
t %F The number of major page faults (page needed to be brought from disk).
t %R The number of minor page faults.
t %I The number of input operations.
t %O The number of output operations.
t %r The number of socket messages received.
t %s The number of socket messages sent.
t %k The number of signals received.
t %w The number of voluntary context switches (waits).
t %c The number of involuntary context switches.
.El
t Fl l Lists resource utilization information.
The contents of the
.Ar command
process's
.Em rusage
structure are printed; see below.
t Fl p The output is formatted as specified by
.St -p1003.2-92 .
t 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

p
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

a /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:
l -item -offset indent -compact t maximum resident set size
t average shared memory size
t average unshared data size
t average unshared stack size
t page reclaims
t page faults
t swaps
t block input operations
t block output operations
t messages sent
t messages received
t signals received
t voluntary context switches
t 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
l -tag -width Xsys/resource.hX -compact t Aq sys/resource.h .El
.Sh EXIT STATUS
The
.Nm
utility exits with one of the following values:
l -tag -width indent t 1-125 An error occurred in the
.Nm
utility.
t 126 The
.Ar command
was found but could not be invoked.
t 127 The
.Ar command
could not be found.
.El

p
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.