*BASH User Commands Ubuntu 10.04.4 LTS Server coreutils
TIME(1)                                                                TIME(1)

       time - run programs and summarize system resource usage

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

       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-

       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

       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-

       -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-
       -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.
              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.

       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)

       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 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
              D      Average size of the  process's  unshared  data  area,  in
              E      Elapsed  real  (wall  clock) time used by the process, in
              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-
              I      Number of file system inputs by the process.
              K      Average   total   (data+stack+text)  memory  use  of  the
                     process, 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-
              X      Average amount of shared text in the  process,  in  Kilo-
              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
              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.

       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 -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

       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.

       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.
       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-

       tcsh(1), printf(3)

                               Debian GNU/Linux                        TIME(1)