TIME(1) 							       TIME(1)



NAME
       time - run programs and summarize system resource usage

SYNOPSIS
       time   [ -apqvV ] [ -f FORMAT ] [ -o FILE ]
	      [ --append ] [ --verbose ] [ --quiet ] [ --portability ]
	      [ --format=FORMAT ] [ --output=FILE ] [ --version ]
	      [ --help ] COMMAND [ ARGS ]

DESCRIPTION
       time  run  the  program	COMMAND with any given arguments ARG....  When
       COMMAND finishes, time displays information  about  resources  used  by
       COMMAND	(on  the standard error output, by default).  If COMMAND exits
       with non-zero status, time displays a warning message and the exit sta-
       tus.

       time  determines  which information to display about the resources used
       by the COMMAND from the string FORMAT.  If no format  is  specified  on
       the  command  line, but the TIME environment variable is set, its value
       is used as the format.  Otherwise, a default format built into time  is
       used.

       Options	to  time must appear on the command line before COMMAND.  Any-
       thing on the command line after COMMAND is passed as arguments to  COM-
       MAND.


OPTIONS
       -o FILE, --output=FILE
	      Write  the  resource  use  statistics  to FILE instead of to the
	      standard error stream.  By default, this	overwrites  the  file,
	      destroying  the file's previous contents.  This option is useful
	      for collecting information on interactive programs and  programs
	      that produce output on the standard error stream.
       -a, --append
	      Append  the  resource use information to the output file instead
	      of overwriting
	       it.  This option is only useful with the `-o' or `--output' op-
	      tion.
       -f FORMAT, --format FORMAT
	      Use  FORMAT  as  the  format  string that controls the output of
	      time.  See the below more information.
       --help Print a summary of the command line options and exit.
       -p, --portability
	      Use the following format	string,  for  conformance  with  POSIX
	      standard 1003.2:
			real %e
			user %U
			sys %S
       -v, --verbose
	      Use  the	built-in verbose format, which displays each available
	      piece of information on the program's resource use  on  its  own
	      line, with an English description of its meaning.
       --quiet
	      Do  not report the status of the program even if it is different
	      from zero.
       -V, --version
	      Print the version number of time and exit.

FORMATTING THE OUTPUT
       The format string FORMAT controls the contents of the time output.  The
       format  string can be set using the `-f' or `--format', `-v' or `--ver-
       bose', or `-p' or `--portability' options.  If they are not given,  but
       the  TIME  environment variable is set, its value is used as the format
       string.	Otherwise, a built-in default format  is  used.   The  default
       format is:
	 %Uuser %Ssystem %Eelapsed %PCPU (%Xtext+%Ddata %Mmax)k
	 %Iinputs+%Ooutputs (%Fmajor+%Rminor)pagefaults %Wswaps

       The  format  string  usually  consists  of `resource specifiers' inter-
       spersed with plain text.  A percent sign (`%')  in  the	format	string
       causes the following character to be interpreted as a resource specifi-
       er, which is similar to the  formatting	characters  in	the  printf(3)
       function.

       A  backslash (`\') introduces a `backslash escape', which is translated
       into a single printing character upon output.  `\t' outputs a tab char-
       acter,  `\n'  outputs a newline, and `\\' outputs a backslash.  A back-
       slash followed by any other character outputs  a  question  mark  (`?')
       followed  by  a backslash, to indicate that an invalid backslash escape
       was given.

       Other text in the format string is copied verbatim to the output.  time
       always prints a newline after printing the resource use information, so
       normally format strings do not end with a newline character (or `0).

       There are many resource specifications.	Not all resources are measured
       by all versions of Unix, so some of the values might be reported as ze-
       ro.  Any character following a percent sign that is not listed  in  the
       table below causes a question mark (`?') to be output, followed by that
       character, to indicate that an invalid resource listed in the table be-
       low causes a question mark (`?') to be output, followed by that charac-
       ter, to indicate that an invalid resource specifier was given.

       The resource specifiers, which are a superset of  those	recognized  by
       the tcsh(1) builtin `time' command, are:
	      %      A literal `%'.
	      C      Name  and	command  line  arguments  of the command being
		     timed.
	      D      Average size of the  process's  unshared  data  area,  in
		     Kilobytes.
	      E      Elapsed  real  (wall  clock) time used by the process, in
		     [hours:]minutes:seconds.
	      F      Number of major, or I/O-requiring, page faults  that  oc-
		     curred  while  the process was running.  These are faults
		     where the page has actually migrated out of primary memo-
		     ry.
	      I      Number of file system inputs by the process.
	      K      Average  total  (data+stack+text)	memory use of the pro-
		     cess, in Kilobytes.
	      M      Maximum resident set size of the process during its life-
		     time, in Kilobytes.
	      O      Number of file system outputs by the process.
	      P      Percentage  of  the  CPU that this job got.  This is just
		     user + system times divided by the total running time. It
		     also prints a percentage sign.
	      R      Number  of minor, or recoverable, page faults.  These are
		     pages that are not valid (so they fault) 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.
	      S      Total  number of CPU-seconds used by the system on behalf
		     of the process (in kernel mode), in seconds.
	      U      Total number of CPU-seconds that the process used direct-
		     ly (in user mode), in seconds.
	      W      Number of times the process was swapped out of main memo-
		     ry.
	      X      Average amount of shared text in the  process,  in  Kilo-
		     bytes.
	      Z      System's  page size, in bytes.  This is a per-system con-
		     stant, but varies between systems.
	      c      Number of times the process was context-switched involun-
		     tarily (because the time slice expired).
	      e      Elapsed  real  (wall  clock) time used by the process, in
		     seconds.
	      k      Number of signals delivered to the process.
	      p      Average unshared stack size of the process, in Kilobytes.
	      r      Number of socket messages received by the process.
	      s      Number of socket messages sent by the process.
	      t      Average resident set size of the process, in Kilobytes.
	      w      Number  of  times	that  the program was context-switched
		     voluntarily, for instance while waiting for an I/O opera-
		     tion to complete.
	      x      Exit status of the command.

EXAMPLES
       To run the command `wc /etc/hosts' and show the default information:
	    time wc /etc/hosts

       To  run	the command `ls -Fs' and show just the user, system, and total
       time:
	    time -f "%E real,%U user,%S sys" ls -Fs

       To edit the file BORK and have `time' append the elapsed time and  num-
       ber  of	signals  to the file `log', reading the format string from the
       environment variable `TIME':
	    export TIME="%E,%k" # If using bash or ksh
	    setenv TIME "%E,%k" # If using csh or tcsh
	    time -a -o log emacs bork

       Users of the bash shell need to use an explicit path in	order  to  run
       the  external time command and not the shell builtin variant. On system
       where time is installed in /usr/bin, the first example would become
	    /usr/bin/time wc /etc/hosts

ACCURACY
       The elapsed time is not collected atomically with the execution of  the
       program;  as  a	result,  in bizarre circumstances (if the time command
       gets stopped or swapped out in between when the program being timed ex-
       its and when time calculates how long it took to run), it could be much
       larger than the actual execution time.

       When the running time of a command is very  nearly  zero,  some	values
       (e.g.,  the  percentage	of  CPU  used)	may be reported as either zero
       (which is wrong) or a question mark.

       Most information shown by time is  derived  from  the  wait3(2)	system
       call.   The numbers are only as good as those returned by wait3(2).  On
       systems that do not have a wait3(2) call that returns  status  informa-
       tion,  the  times(2) system call is used instead.  However, it provides
       much less information than wait3(2), so on those systems  time  reports
       the majority of the resources as zero.

       The `%I' and `%O' values are allegedly only `real' input and output and
       do not include those supplied by caching devices.  The meaning of  `re-
       al'  I/O reported by `%I' and `%O' may be muddled for workstations, es-
       pecially diskless ones.

DIAGNOSTICS
       The time command returns when the program exits, stops, or is terminat-
       ed  by  a  signal.  If the program exited normally, the return value of
       time is the return value of the program it executed and measured.  Oth-
       erwise,	the  return  value  is 128 plus the number of the signal which
       caused the program to stop or terminate.
AUTHOR
       time was written by David MacKenzie. This man page was  added  by  Dirk
       Eddelbuettel <edd@debian.org>, the Debian GNU/Linux maintainer, for use
       by the Debian GNU/Linux distribution but may of course be used by  oth-
       ers.

SEE ALSO
       tcsh(1), printf(3)



			       Debian GNU/Linux 		       TIME(1)