This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface

       The command, env, nice, nohup, time, and xargs utilities have been specified to use exit code 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. Some scripts produce meaningful error messages
       differentiating the 126 and 127 cases. The distinction between  exit  codes  126  and  127  is  based  on
       KornShell  practice  that uses 127 when all attempts to exec the utility fail with [ENOENT], and uses 126
       when any attempt to exec the utility fails for any other reason.

       Default.

       Default.

       Thefollowingsectionsareinformative.

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
       for Information  Technology  --  Portable  Operating  System  Interface  (POSIX),  The  Open  Group  Base
       Specifications  Issue  7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics
       Engineers, Inc and The Open Group.  In the event of any discrepancy between this version and the original
       IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee  document.
       The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

       Any  typographical  or formatting errors that appear in this page are most likely to have been introduced
       during  the  conversion  of  the  source  files  to  man  page  format.  To  report  such   errors,   see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                                   2017                                          TIME(1POSIX)

       The  time  utility  shall  invoke the utility named by the utility operand with arguments supplied as the
       argument operands and write a message to standard error that lists timing statistics for the utility. The
       message shall include the following information:

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

        *  The User CPU time, equivalent to the sum of the tms_utime  and  tms_cutime  fields  returned  by  the
           times()  function  defined  in  the System Interfaces volume of POSIX.1‐2017 for the process in which
           utility is executed.

        *  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.

       The  precision of the timing shall be no less than the granularity defined for the size of the clock tick
       unit on the system, but the results shall be reported in terms of standard time units (for example,  0.02
       seconds, 00:00:00.02, 1m33.75s, 365.21 seconds), not numbers of clock ticks.

       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 (see Section2.9.4.1, GroupingCommands) 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)

       The following environment variables shall affect the execution of time:

       LANG      Provide a default value for the internationalization variables that are unset or null. (See the
                 Base  Definitions  volume  of POSIX.1‐2017, Section8.2, InternationalizationVariables for the
                 precedence  of  internationalization  variables  used  to  determine  the  values   of   locale
                 categories.)

       LC_ALL    If  set  to a non-empty string value, override the values of all the other internationalization
                 variables.

       LC_CTYPE  Determine the locale for the interpretation of sequences of bytes of text  data  as  characters
                 (for example, single-byte as opposed to multi-byte characters in arguments).

       LC_MESSAGES
                 Determine  the  locale  that should be used to affect the format and contents of diagnostic and
                 informative messages written to standard error.

       LC_NUMERIC
                 Determine the locale for numeric formatting.

       NLSPATH   Determine the location of message catalogs for the processing of LC_MESSAGES.

       PATH      Determine the search path that shall be used to locate the utility to be invoked; see the  Base
                 Definitions volume of POSIX.1‐2017, Chapter8, EnvironmentVariables.

       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 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:

           time sh -c 'complex-command-line'

       If  the  utility  utility  is  invoked,  the  exit  status  of  time shall be the exit status of utility;
       otherwise, the time utility shall exit with one of the following values:

       1‐125   An error occurred in the time utility.

         126   The utility specified by utility was found but could not be invoked.

         127   The utility specified by utility could not be found.

       None.

       None.

       None.

       time — time a simple command

       The following operands shall be supported:

       utility   The  name  of  a utility that is to be invoked. If the utility operand names any of the special
                 built-in utilities in Section2.14, SpecialBuilt-InUtilities, the results are undefined.

       argument  Any string to be supplied as an argument  when  invoking  the  utility  named  by  the  utility
                 operand.

       The time utility shall conform to the Base Definitions volume  of  POSIX.1‐2017,  Section12.2,  UtilitySyntaxGuidelines.

       The following option shall be supported:

       -p        Write the timing output to standard error in the format shown in the STDERR section.

       None.

       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of this interface
       may differ (consult the corresponding Linux manual page for details of Linux behavior), or the  interface
       may not be implemented on Linux.

       When the time utility was originally proposed to be included in the ISO POSIX‐2:1993 standard,  questions
       were  raised  about  its  suitability  for inclusion on the grounds that it was not useful for conforming
       applications, specifically:

        *  The underlying CPU definitions from the System Interfaces volume of POSIX.1‐2017 are  vague,  so  the
           numeric output could not be compared accurately between systems or even between invocations.

        *  The creation of portable benchmark programs was outside the scope this volume of POSIX.1‐2017.

       However,  time  does fit in the scope of user portability. Human judgement can be applied to the analysis
       of the output, and it could be very  useful  in  hands-on  debugging  of  applications  or  in  providing
       subjective measures of system performance. Hence it has been included in this volume of POSIX.1‐2017.

       The  default output format has been left unspecified because historical implementations differ greatly in
       their style of depicting this numeric output. The -p option was invented to provide scripts with a common
       means of obtaining this information.

       In the KornShell, time is a shell reserved word that can be used to time an entire pipeline, rather  than
       just  a  simple command. The POSIX definition has been worded to allow this implementation. Consideration
       was given to invalidating this approach because of the historical model from the C  shell  and  System  V
       shell.  However,  since  the  System  V  time  utility  historically has not produced accurate results in
       pipeline timing (because the constituent processes are not all owned  by  the  same  parent  process,  as
       allowed by POSIX), it did not seem worthwhile to break historical KornShell usage.

       The  term  utility  is  used,  rather  than  command, to highlight the fact that shell compound commands,
       pipelines, special built-ins, and so on,  cannot  be  used  directly.   However,  utility  includes  user
       application programs and shell scripts, not just the standard utilities.

Chapter2, ShellCommandLanguage, sh

       The  Base  Definitions  volume  of  POSIX.1‐2017, Chapter8, EnvironmentVariables, Section12.2, UtilitySyntaxGuidelines

       The System Interfaces volume of POSIX.1‐2017, times()

       If  the  utility  utility is invoked, the standard error shall be used to write the timing statistics and
       may be used to write a diagnostic message if the utility terminates abnormally; otherwise,  the  standard
       error shall be used to write diagnostic messages and may also be used to write the timing statistics.

       If -p is specified, the following format shall be used for the timing statistics in the POSIX locale:

           "real %f\nuser %f\nsys %f\n", <realseconds>, <userseconds>,
               <systemseconds>

       where  each  floating-point number shall be expressed in seconds. The precision used may be less than the
       default six digits of %f, but shall be sufficiently precise to accommodate the size of the clock tick  on
       the  system  (for  example, if there were 60 clock ticks per second, at least two digits shall follow the
       radix character). The number of digits following the radix character shall be no less than one,  even  if
       this  always  results  in  a  trailing  zero.  The  implementation  may append white space and additional
       information following the format shown here. The implementation may also  prepend  a  single  empty  line
       before the format shown here.

       Not used.

       Not used.

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