time

TIME(1)                     General Commands Manual                    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
       status.

       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.
       Anything on the command line after COMMAND is passed as arguments to
       COMMAND.

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' option.

       -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
       `--verbose', 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'
       interspersed with plain text.  A percent sign (`%') in the format
       string causes the following character to be interpreted as a resource
       specifier, 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
       character, `\n' outputs a newline, and `\\' outputs a backslash.  A
       backslash 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 `\n').

       There are many resource specifications.  Not all resources are measured
       by all versions of Unix, so some of the values might be reported as
       zero.  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
                     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
                     occurred while the process was running.  These are faults
                     where the page has actually migrated out of primary
                     memory.
              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
                     lifetime, 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
                     directly (in user mode), in seconds.
              W      Number of times the process was swapped out of main
                     memory.

              X      Average amount of shared text in the process, in
                     Kilobytes.
              Z      System's page size, in bytes.  This is a per-system
                     constant, but varies between systems.
              c      Number of times the process was context-switched
                     involuntarily (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
                     operation 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 "\t%E real,\t%U user,\t%S sys" ls -Fs

       To edit the file BORK and have `time' append the elapsed time and
       number of signals to the file `log', reading the format string from the
       environment variable `TIME':
            export TIME="\t%E,\t%k" # If using bash or ksh
            setenv TIME "\t%E,\t%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
       exits 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
       information, 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
       `real' I/O reported by `%I' and `%O' may be muddled for workstations,
       especially diskless ones.

DIAGNOSTICS
       The time command returns when the program exits, stops, or is
       terminated by a signal.  If the program exited normally, the return
       value of time is the return value of the program it executed and
       measured.  Otherwise, 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
       others.

SEE ALSO
       tcsh(1), printf(3)

                               Debian GNU/Linux                        TIME(1)