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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 com-
       mand 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 suffi-
              cient 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 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 sys-
              tem 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 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 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-utilsATprep.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 informa-
       tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



                                  2008-11-14                           TIME(1)