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 termi-
       nation, (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 sys-
       tem 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
user %f
sys %f
"

	      (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 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  	,  
  and  \,  a  percent 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  com-
	      plete.

       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 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 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 path-
       names) 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 3.25 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)