time(1) — Linux manual page


TIME(1)                      Linux User's Manual                     TIME(1)

NAME         top

       time - time a simple command or give resource usage

SYNOPSIS         top

       time [options] command [arguments...]

DESCRIPTION         top

       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         top

       -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         top

       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         top

       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         top

       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.


       %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

       %U     Total number of CPU-seconds that the process spent in user

       %P     Percentage of the CPU that this job got, computed as (%U + %S)
              / %E.


       %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

       %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     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 com‐
              mand 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 speci‐
              fied 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

       -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 success‐

       -V, --version
              Print version information on standard output, then exit suc‐

       --     Terminate option list.

BUGS         top

       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         top

       bash(1), tcsh(1), times(2), wait3(2)

COLOPHON         top

       This page is part of release 5.08 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

                                 2019-03-06                          TIME(1)

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