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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXIT STATUS | ENVIRONMENT | GNU VERSION | BUGS | SEE ALSO | COLOPHON |
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TIME(1) Linux User's Manual TIME(1)
time - time a simple command or give resource usage
time [options] command [arguments...]
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).
-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.
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.
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.
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 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
file.
-a, --append
(Used together with -o.) Do not overwrite but append.
-v, --verbose
Give very verbose output about all the program knows about.
GNU standard options
--help Print a usage message on standard output and exit success‐
fully.
-V, --version
Print version information on standard output, then exit suc‐
cessfully.
-- Terminate option list.
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-utils@prep.ai.mit.edu. Please include the version of time, which
you can get by running
time --version
and the operating system and C compiler you used.
bash(1), tcsh(1), times(2), wait3(2)
This page is part of release 4.15 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/.
2017-09-15 TIME(1)
Pages that refer to this page: strace(1), times(2), time(7)
Copyright and license for this manual page
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