# time

## NAME



           time - time a simple command or give resource usage
    


## SYNOPSIS



           **time**[_option_ ...] _command_ [_argument_ ...]
    


## 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_.
    


## 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(3)-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.
    


* * *