time

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 similar information on the usage of time and possibly other
       resources.  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 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, and
       NLSPATH are used for the text and formatting of the output.  PATH is used
       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 is used:

           real %e
           user %U
           sys %S

   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(1).)  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(1).)  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(1).)  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(1).)  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(1).)  Name and command-line arguments of the command
              being timed.

       %x     (Not in tcsh(1).)  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.

       -q, --quiet
              Don't report abnormal program termination (where command is
              terminated by a signal) or nonzero exit status.

   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-time@gnu.org.
       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
       bash(1), tcsh(1), times(2), wait3(2)

COLOPHON
       This page is part of release 5.10 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at
       https://www.kernel.org/doc/man-pages/.



                                   2019-03-06                            TIME(1)