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Linux 2.6 - man page for time (linux section 1)

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 com-
       mand 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  func-
       tionality  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 com-
       mand could not be found, 126 if it could be found but could not be invoked, and some other
       nonzero 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 percent sign is rep-
       resented  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 sup-
       ported.

       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 filesystem inputs by the process.

       %O     Number of filesystem 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 environment
	      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 provided by 4.2
       or 4.3BSD.

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

       The  environment variable TIME was badly chosen.  It is not unusual for systems like auto-
       conf(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@prep.ai.mit.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 3.55 of the Linux man-pages project.  A description of the
       project,    and	  information	 about	  reporting    bugs,	can    be    found     at
       http://www.kernel.org/doc/man-pages/.

					    2008-11-14					  TIME(1)


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