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TIME(1)                       Linux User's Manual                      TIME(1)



NAME
       time - time a simple command or give resource usage

SYNOPSIS
       time [options] command [arguments...]

DESCRIPTION
       The time command runs the specified program command with the given arguments.  When
       command finishes, time writes a message to standard error giving timing  statistics
       about  this  program  run.   These  statistics consist of (i) the elapsed real time
       between invocation and termination,  (ii)  the  user  CPU  time  (the  sum  of  the
       tms_utime and tms_cutime values in a struct tms as returned by times(2)), and (iii)
       the system CPU time (the sum of the tms_stime and tms_cstime values in a struct tms
       as returned by times(2)).

       Note:  some  shells (e.g., bash(1)) have a built-in time command that provides less
       functionality than the command described here.  To access the real command, you may
       need to specify its pathname (something like /usr/bin/time).

OPTIONS
       -p     When in the POSIX locale, use the precise traditional format

                  "real %f\nuser %f\nsys %f\n"

              (with  numbers in seconds) where the number of decimals in the output for %f
              is unspecified but is sufficient to express the clock tick accuracy, and  at
              least one.

EXIT STATUS
       If command was invoked, the exit status is that of command.  Otherwise it is 127 if
       command could not be found, 126 if it could be found but could not be invoked,  and
       some other non-zero value (1-125) if something else went wrong.

ENVIRONMENT
       The  variables  LANG,  LC_ALL, LC_CTYPE, LC_MESSAGES, LC_NUMERIC, NLSPATH, and PATH
       are used.  The last one to search for command.  The remaining ones for the text and
       formatting of the output.

GNU VERSION
       Below  a  description of the GNU 1.7 version of time.  Disregarding the name of the
       utility, GNU makes it output lots of useful information, not only about time  used,
       but  also on other resources like memory, I/O and IPC calls (where available).  The
       output is formatted using a format string that can be specified using the -f option
       or the TIME environment variable.

       The default format string is:

           %Uuser %Ssystem %Eelapsed %PCPU (%Xtext+%Ddata %Mmax)k
           %Iinputs+%Ooutputs (%Fmajor+%Rminor)pagefaults %Wswaps

       When the -p option is given the (portable) output format

           real %e
           user %U
           sys %S

       is used.

   The format string
       The  format  is  interpreted in the usual printf-like way.  Ordinary characters are
       directly copied, tab, newline and backslash are escaped using \t, \n and \\, a per-
       cent  sign  is  represented  by  %%,  and  otherwise % indicates a conversion.  The
       program time will always add a trailing newline itself.   The  conversions  follow.
       All of those used by tcsh(1) are supported.

       Time

       %E     Elapsed real time (in [hours:]minutes:seconds).

       %e     (Not in tcsh.) Elapsed real time (in seconds).

       %S     Total number of CPU-seconds that the process spent in kernel mode.

       %U     Total number of CPU-seconds that the process spent in user mode.

       %P     Percentage of the CPU that this job got, computed as (%U + %S) / %E.

       Memory

       %M     Maximum resident set size of the process during its lifetime, in Kbytes.

       %t     (Not in tcsh.) Average resident set size of the process, in Kbytes.

       %K     Average total (data+stack+text) memory use of the process, in Kbytes.

       %D     Average size of the process's unshared data area, in Kbytes.

       %p     (Not  in  tcsh.)  Average  size  of  the  process's unshared stack space, in
              Kbytes.

       %X     Average size of the process's shared text space, in Kbytes.

       %Z     (Not in tcsh.) System's page size, in bytes.  This is a per-system constant,
              but varies between systems.

       %F     Number  of  major  page  faults that occurred while the process was running.
              These are faults where the page has to be read in from disk.

       %R     Number of minor, or recoverable, page faults.  These are  faults  for  pages
              that  are  not  valid  but  which have not yet been claimed by other virtual
              pages.  Thus the data in the page is still valid but the system tables  must
              be updated.

       %W     Number of times the process was swapped out of main memory.

       %c     Number  of times the process was context-switched involuntarily (because the
              time slice expired).

       %w     Number of waits: times that the program  was  context-switched  voluntarily,
              for instance while waiting for an I/O operation to complete.

       I/O

       %I     Number of file system inputs by the process.

       %O     Number of file system outputs by the process.

       %r     Number of socket messages received by the process.

       %s     Number of socket messages sent by the process.

       %k     Number of signals delivered to the process.

       %C     (Not in tcsh.) Name and command-line arguments of the command being timed.

       %x     (Not in tcsh.) Exit status of the command.

   GNU Options
       -f FORMAT, --format=FORMAT
              Specify output format, possibly overriding the format specified in the envi-
              ronment variable TIME.

       -p, --portability
              Use the portable output format.

       -o FILE, --output=FILE
              Do not send the results to stderr, but overwrite the specified file.

       -a, --append
              (Used together with -o.) Do not overwrite but append.

       -v, --verbose
              Give very verbose output about all the program knows about.

   GNU Standard Options
       --help Print a usage message on standard output and exit successfully.

       -V, --version
              Print version information on standard output, then exit successfully.

       --     Terminate option list.

BUGS
       Not all resources are measured by all versions of Unix, so some of the values might
       be  reported  as  zero.  The present selection was mostly inspired by the data pro-
       vided by 4.2 or 4.3BSD.

       GNU time version 1.7 is not yet localized.  Thus, it does not implement  the  POSIX
       requirements.

       The environment variable TIME was badly chosen.  It is not unusual for systems like
       autoconf(1) or make(1) to use environment variables with the name of a  utility  to
       override  the  utility  to be used.  Uses like MORE or TIME for options to programs
       (instead of program pathnames) tend to lead to difficulties.

       It seems unfortunate that -o overwrites instead  of  appends.   (That  is,  the  -a
       option should be the default.)

       Mail suggestions and bug reports for GNU time to
       bug-utils AT prep.edu
       Please include the version of time, which you can get by running
       time --version
       and the operating system and C compiler you used.

SEE ALSO
       tcsh(1), times(2), wait3(2)

COLOPHON
       This page is part of release 3.22 of the Linux man-pages project.  A description of
       the project, and information about reporting bugs, can be found at  http://www.ker-
       nel.org/doc/man-pages/.



                                  2008-11-14                           TIME(1)

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