TIME(1)                                                                                                                                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 `0).

       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 "%E real,%U user,%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="%E,%k" # If using bash or ksh
            setenv TIME "%E,%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)
 

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