TIME(1) User Commands TIME(1)

NAME

time - time a simple command

SYNOPSIS

time [-p] utility [argument]...

DESCRIPTION

The time utility invokes utility operand with argument, and writes a
message to standard error that lists timing statistics for utility. The
message includes the following information:

o The elapsed (real) time between invocation of utility and its
termination.

o The User CPU time, equivalent to the sum of the tms_utime and
tms_cutime fields returned by the times(2) function for the
process in which utility is executed.

o The System CPU time, equivalent to the sum of the tms_stime
and tms_cstime fields returned by the times() function for the
process in which utility is executed.


When time 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 a and c, respectively:

time a | b | c { time a } | b | c
a | b | time c a | b | (time c)

OPTIONS

The following option is supported:

-p
Writes the timing output to standard error in the following
format:

real %f\nuser %f\nsys %f\n < real seconds>, <user seconds>,
<system seconds>

OPERANDS

The following operands are supported:

utility
The name of the utility that is to be invoked.


argument
Any string to be supplied as an argument when invoking
utility.

USAGE

The time utility returns exit status 127 if an error occurs so that
applications can distinguish "failure to find a utility" from "invoked
utility exited with an error indication." The value 127 was chosen
because it is not commonly used for other meanings. Most utilities use
small values for "normal error conditions" and the values above 128 can
be confused with termination due to receipt of a signal. The value 126
was chosen in a similar manner to indicate that the utility could be
found, but not invoked.

EXAMPLES

Example 1: Using the time command

It is frequently desirable to apply time 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
time applies to everything in the file.


Alternatively, the following command can be used to apply time to a
complex command:


example% time sh -c 'complex-command-line'

Example 2: Using time in the csh shell

The following two examples show the differences between the csh version
of time and the version in /usr/bin/time. These examples assume that csh
is the shell in use.


example% time find / -name csh.1 -print
/usr/share/man/man1/csh.1
95.0u 692.0s 1:17:52 16% 0+0k 0+0io 0pf+0w


See csh(1) for an explanation of the format of time output.


example% /usr/bin/time find / -name csh.1 -print
/usr/share/man/man1/csh.1
real 1:23:31.5
user 1:33.2
sys 11:28.2

ENVIRONMENT VARIABLES

See environ(7) for descriptions of the following environment variables
that affect the execution of time: LANG, LC_ALL, LC_CTYPE, LC_MESSAGES,
LC_NUMERIC, NLSPATH, and PATH.

EXIT STATUS

If utility is invoked, the exit status of time will be the exit status of
utility. Otherwise, the time utility will exit with one of the following
values:

1-125
An error occurred in the time utility.


126
utility was found but could not be invoked.


127
utility could not be found.

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Standard |
+--------------------+-----------------+

SEE ALSO

csh(1), shell_builtins(1), timex(1), times(2), attributes(7), environ(7),
standards(7)

NOTES

When the time command is run on a multiprocessor machine, the total of
the values printed for user and sys can exceed real. This is because on a
multiprocessor machine it is possible to divide the task between the
various processors.


When the command being timed is interrupted, the timing values displayed
may not always be accurate.

BUGS

Elapsed time is accurate to the second, while the CPU times are measured
to the 100th second. Thus the sum of the CPU times can be up to a second
larger than the elapsed time.

February 1, 1995 TIME(1)