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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 statis-
     tics for utility. The message includes the following  infor-
     mation:

         o    The elapsed (real) time between invocation of util-
              ity 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  indica-
     tion."  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(5) 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(5) for descriptions of the  following  attri-
     butes:



     tab() box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i)  ATTRI-
     BUTE  TYPEATTRIBUTE  VALUE  _  Availabilitysystem/core-os  _
     Interface StabilityCommitted _ StandardSee standards(5).

See Also
     csh(1),  shell_builtins(1),   timex(1),   times(2),   attributes(5),
     environ(5), standards(5)

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.
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