path: root/usr/src/man/man1/time.1

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.TH TIME 1 "Feb 1, 1995"
.SH NAME
time \- time a simple command
.SH SYNOPSIS
.LP
.nf
\fBtime\fR [\fB-p\fR] \fIutility\fR [\fIargument\fR]...
.fi

.SH DESCRIPTION
.sp
.LP
The \fBtime\fR utility invokes \fIutility\fR operand with \fIargument\fR, and
writes a message to standard error that lists timing statistics for
\fIutility\fR. The message includes the following information:
.RS +4
.TP
.ie t \(bu
.el o
The elapsed (real) time between invocation of \fIutility\fR and its
termination.
.RE
.RS +4
.TP
.ie t \(bu
.el o
The User \fBCPU\fR time, equivalent to the sum of the \fItms_utime\fR and
\fItms_cutime\fR fields returned by the \fBtimes\fR(2) function for the process
in which \fIutility\fR is executed.
.RE
.RS +4
.TP
.ie t \(bu
.el o
The System \fBCPU\fR time, equivalent to the sum of the \fItms_stime\fR and
\fItms_cstime\fR fields returned by the \fBtimes()\fR function for the process
in which \fIutility\fR is executed.
.RE
.sp
.LP
When \fBtime\fR is used as part of a pipeline, the times reported are
unspecified, except when it is the sole command within a grouping command in
that pipeline. For example, the commands on the left are unspecified; those on
the right report on utilities \fBa\fR and \fBc\fR, respectively:
.sp
.in +2
.nf
time a | b | c		{ time a } | b | c
a | b | time c		a | b | (time c)
.fi
.in -2

.SH OPTIONS
.sp
.LP
The following option is supported:
.sp
.ne 2
.na
\fB\fB-p\fR \fR
.ad
.RS 7n
Writes the timing output to standard error in the following format:
.sp
.in +2
.nf
real %f\enuser %f\ensys %f\en < \fIreal seconds\fR>, <\fIuser seconds\fR>,
<\fIsystem seconds\fR>
.fi
.in -2
.sp

.RE

.SH OPERANDS
.sp
.LP
The following operands are supported:
.sp
.ne 2
.na
\fB\fIutility\fR \fR
.ad
.RS 13n
The name of the utility that is to be invoked.
.RE

.sp
.ne 2
.na
\fB\fIargument\fR \fR
.ad
.RS 13n
Any string to be supplied as an argument when invoking \fIutility\fR.
.RE

.SH USAGE
.sp
.LP
The \fBtime\fR utility returns exit status \fB127\fR if an error occurs so that
applications can distinguish "failure to find a utility" from "invoked utility
exited with an error indication." The value \fB127\fR was chosen because it is
not commonly used for other meanings. Most utilities use small values for
"normal error conditions" and the values above \fB128\fR can be confused with
termination due to receipt of a signal. The value \fB126\fR was chosen in a
similar manner to indicate that the utility could be found, but not invoked.
.SH EXAMPLES
.LP
\fBExample 1 \fRUsing the time command
.sp
.LP
It is frequently desirable to apply \fBtime\fR to pipelines or lists of
commands. This can be done by placing pipelines and command lists in a single
file. This single file can then be invoked as a utility, and the \fBtime\fR
applies to everything in the file.

.sp
.LP
Alternatively, the following command can be used to apply \fBtime\fR to a
complex command:

.sp
.in +2
.nf
example% \fBtime sh -c 'complex-command-line'\fR
.fi
.in -2
.sp

.LP
\fBExample 2 \fRUsing time in the csh shell
.sp
.LP
The following two examples show the differences between the \fBcsh\fR version
of \fBtime\fR and the version in \fB/usr/bin/time\fR. These examples assume
that \fBcsh\fR is the shell in use.

.sp
.in +2
.nf
example% \fBtime find / -name csh.1 -print
/usr/share/man/man1/csh.1\fR
95.0u 692.0s 1:17:52 16% 0+0k 0+0io 0pf+0w
.fi
.in -2
.sp

.sp
.LP
See \fBcsh\fR(1) for an explanation of the format of \fBtime\fR output.

.sp
.in +2
.nf
example% \fB/usr/bin/time find / -name csh.1 -print
/usr/share/man/man1/csh.1\fR
real  1:23:31.5
user     1:33.2
sys     11:28.2
.fi
.in -2
.sp

.SH ENVIRONMENT VARIABLES
.sp
.LP
See \fBenviron\fR(5) for descriptions of the following environment variables
that affect the execution of \fBtime\fR: \fBLANG\fR, \fBLC_ALL\fR,
\fBLC_CTYPE\fR, \fBLC_MESSAGES\fR, \fBLC_NUMERIC\fR,  \fBNLSPATH\fR, and
\fBPATH\fR.
.SH EXIT STATUS
.sp
.LP
If \fIutility\fR is invoked, the exit status of \fBtime\fR will be the exit
status of \fIutility\fR. Otherwise, the \fBtime\fR utility will exit with one
of the following values:
.sp
.ne 2
.na
\fB\fB1\(mi125\fR \fR
.ad
.RS 13n
An error occurred in the \fBtime\fR utility.
.RE

.sp
.ne 2
.na
\fB\fB126\fR \fR
.ad
.RS 13n
\fIutility\fR was found but could not be invoked.
.RE

.sp
.ne 2
.na
\fB\fB127\fR \fR
.ad
.RS 13n
\fIutility\fR could not be found.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
.TE

.SH SEE ALSO
.sp
.LP
\fBcsh\fR(1), \fBshell_builtins\fR(1), \fBtimex\fR(1), \fBtimes\fR(2),
\fBattributes\fR(5), \fBenviron\fR(5), \fBstandards\fR(5)
.SH NOTES
.sp
.LP
When the time command is run on a multiprocessor machine, the total of the
values printed for \fBuser\fR and \fBsys\fR can exceed \fBreal\fR. This is
because on a multiprocessor machine it is possible to divide the task between
the various processors.
.sp
.LP
When the command being timed is interrupted, the timing values displayed may
not always be accurate.
.SH BUGS
.sp
.LP
Elapsed time is accurate to the second, while the \fBCPU\fR times are measured
to the 100th second. Thus the sum of the \fBCPU\fR times can be up to a second
larger than the elapsed time.