run programs and summarize system resource usage
see also :
[ -apqvV ] [
-f FORMAT ] [ -o
[ --append ]
[ --verbose ] [
--quiet ] [
[ --format=FORMAT ] [
--output=FILE ] [
[ --help ] COMMAND [ ARGS
add an example, a script, a trick and tips
To run the command ’wc /etc/hosts’ and show the
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
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
Network latency measurement (Linux)
Run you program and the meantime capture network traffic with
wireshark. Check the time of
the request and the reply and do a simple subtraction.
Linux - Forcing 24-hour locale?
Locales can be set for various components separately, so you can
LC_TIME to either
en_GB.utf-8" (Great Britain) or
C" (no locale at all).
(Don't forget /etc/locale.gen.)
Fastest booting desktop linux distro?
PuppyLinux, xPUD and DSL should be fast.
Ext4 support needs to be checked though.
Also consider things like XFCE.
how long to zero a drive with dd?
I'm guessing, but my guess is that it would depend on the drive
controller, the controller on the motherboard, and what else is
soaking up CPU/IO.
My guess, on the order of hour or hours. Days seems long.
Depending on how your machine is set up, running both at the same
time may actually slow things down if you create contention for
the drive controller. Even though you're pumping out zeros,
nothing in your drive knows that and it needs to write every
How can I permanently fix my date synchronize problem in linux?
I had the same problem yesterday but under Slackware 8. To make a
long story short, I read a lot on google to finally reimage the
computer. My manager sent me that link but it did not fixed my issue.
I changed the local to UTC time. I changed the timezome to have
the good one I ln both.
Hope this will help you!
Also, you can try this:
Timezone conversion by command line
This example is from http://www.pixelbeat.org/cmdline.html#dates
It gives the local time corresponding to 9AM on the west coast of
the US, accounting for differing day light savings transitions.
date --date='TZ="America/Los_Angeles" 09:00 next Fri'
Use tzselect to get the TZ. The PST format is ambiguous. IST =
Indian Standard Time and Irish Summer Time for example.
Is there any command like time, but for memory usage?
time can report a bit more information than the version built
into Bash; use
command time rather than just
time to invoke it, and see the man page or info for
Time changes when using two OSs
It's probably because Ubuntu is configured to assume that the
system clock is GMT/UTC (or whatever you want to call it) and it
adjusts the time zone for the location of the user that is
logging in. Windows changes the actual system clock to match the
time zone. You can reconfigure Ubuntu to assume that the system
clock is local time, but I can't remember how to do it at the
moment (google will tell you!).
How to set Debian to automatically update time and date?
Install ntp and made it run on runlevels 2,3,5. Then it will pull
the date and time from well-known sources and will adjust your
Get the time it took to execute the previous command in linux(without re-executing that command)
If you run around the block and don't measure the amount of time
it took, didn't watch any clocks before, during or after and no
people saw you do it, you also don't know how long it takes on
average; would you be able to tell how long it took you to run
around the block?
At best, you can know when you launched a certain application.
HISTTIMEFORMAT="%F %T " history
But that doesn't tell you when it has ended, which you will need
to deduce, if at all possible.
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.
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.
time must appear on the command line before
COMMAND. Anything on the command line after
COMMAND is passed as arguments to COMMAND.
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.
Append the resource use
information to the output file instead of overwriting it.
This option is only useful with the ’-o’
or ’--output’ option.
Use FORMAT as the format
string that controls the output of time. See the
below more information.
Print a summary of the command line options and
Use the following format
string, for conformance with POSIX standard 1003.2:
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.
Do not report the status of the
program even if it is different from zero.
Print the version number of
time and exit.
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
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.
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
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)
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 ’%’.
Name and command line arguments of the command being timed.
Average size of the process’s unshared data area, in
Elapsed real (wall clock) time used by the process, in
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.
Number of file system inputs by the process.
Average total (data+stack+text) memory use of the process, in
Maximum resident set size of the process during its lifetime, in
Number of file system outputs by the process.
Percentage of the CPU that this job got. This is just user +
system times divided by the total running time. It also prints a
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.
Total number of CPU-seconds used by the system on behalf of the
process (in kernel mode), in seconds.
Total number of CPU-seconds that the process used directly (in
user mode), in seconds.
Number of times the process was swapped out of main memory.
Average amount of shared text in the process, in Kilobytes.
System’s page size, in bytes. This is a per-system
constant, but varies between systems.
Number of times the process was context-switched involuntarily
(because the time slice expired).
Elapsed real (wall clock) time used by the process, in seconds.
Number of signals delivered to the process.
Average unshared stack size of the process, in Kilobytes.
Number of socket messages received by the process.
Number of socket messages sent by the process.
Average resident set size of the process, in Kilobytes.
Number of times that the program was context-switched
voluntarily, for instance while waiting for an I/O operation to
Exit status of the command.
time was written by
David MacKenzie. This man page was added by Dirk
Eddelbuettel <edd[:at:]debian[:dot:]org>, the Debian GNU/Linux
maintainer, for use by the Debian GNU/Linux distribution but
may of course be used by others.