time命令小结

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When the -p option is given the (portable) output format

real %e

user %U

sys %S

time - time a simple command or give resource usage #一个简单的命令或提供资源使用

[root@mode ~]# time

real 0m0.000s

user 0m0.000s

sys 0m0.000s

%e (Not in tcsh.) Elapsed real time (in seconds). #(不是在tcsh。)真正的时间(以秒为单位)。

%S Total number of CPU-seconds that the process spent in kernel mode. #CPU在内核模式的过程中秒总数。

%U Total number of CPU-seconds that the process spent in user mode. #CPU在用户模式的过程中秒总数。

1)实际时间(real time): 从command命令行开始执行到运行终止的消逝时间；

2)用户CPU时间(user CPU time): 命令执行完成花费的用户CPU时间，即命令在用户态中执行时间总和；

3)系统CPU时间(system CPU time): 命令执行完成花费的系统CPU时间，即命令在核心态中执行时间总和。

其中，用户CPU时间和系统CPU时间之和为CPU时间，即命令占用CPU执行的时间总和。实际时间要大于CPU时间，因为Linux是多任务操作系统，往往在执行一条命令时，系统还要处理其它任务。

使用-p 参数后的时间显示格式为NN.FF，其单位为秒。

[root@mode ~]# time -p find . -name "mysql.sh"

real 0.00

user 0.00

sys 0.00

[root@mode ~]# man time

TIME(1) TIME(1)

NAME

time - time a simple command or give resource usage

SYNOPSIS

time [options] command [arguments...]

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 less functionality than the command

described here. To access the real command, you may need to specify its pathname (something like

/usr/bin/time).

OPTION

-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 suffi-

cient to express the clock tick accuracy, and at least one.

ENVIRONMENT

The variables LANG, LC_ALL, LC_CTYPE, LC_MESSAGES, LC_NUMERIC, NLSPATH and PATH are used. The last one to search

for command. The remaining ones for the text and formatting of the output.

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 non-zero value (1-125) if something else went

wrong.

SEE ALSO

times(2)

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

real %e

user %U

sys %S

is used.

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). #真正的时间((小时:分钟:秒)。

%e (Not in tcsh.) Elapsed real time (in seconds). #(不是在tcsh。)真正的时间(以秒为单位)。

%S Total number of CPU-seconds that the process spent in kernel mode. #CPU在内核模式的过程中秒总数。

%U Total number of CPU-seconds that the process spent in user mode. #CPU在用户模式的过程中秒总数。 Sat May 31 22:24:40 2014

%P Percentage of the CPU that this job got, computed as (%U + %S) / %E. #比例的CPU,这份工作,计算(% U + % S)/ % E。

Memory

%M Maximum resident set size of the process during its lifetime, in Kbytes. #在运行周期内最大驻留集的进程,单位是kb。

%t (Not in tcsh.) Average resident set size of the process, in Kbytes. #(不是在tcsh。)平均驻留集大小在进程中,单位是kb。

%K Average total (data+stack+text) memory use of the process, in Kbytes. #平均总(数据+栈+文本)进程的内存使用,在kb。

%D Average size of the process‘s unshared data area, in Kbytes. #进程的平均尺寸的非共享数据区

%p (Not in tcsh.) Average size of the process‘s unshared stack space, in Kbytes. #(不是在tcsh。)过程的平均尺寸的非共享栈空间,在kb。

%X Average size of the process‘s shared text space, in Kbytes. #进程的共享文本空间的平均大小,kb。

%Z (Not in tcsh.) System‘s page size, in bytes. This is a per-system constant, but varies between systems.

#(不是在tcsh。)系统的页面大小,以字节为单位。这是一个系统级别的常数,但不同系统之间。

%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.

#一些主要的页面错误,在进程执行过程中发生。这些都是错误的页面必须从磁盘读取。

%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 sys-

tem tables must be updated.

#小的数量,或可恢复,页面错误。这些错误的页面是无效的,但还没有被其他虚拟页面声称。因此页面中的数据仍然有效,但必须更新系统表。

%W Number of times the process was swapped out of main memory.

#次数时间的进程被换出内存。

%c Number of times the process was context-switched involuntarily (because the time slice expired).

#进程上下文切换的次数不自觉地(因为时间片过期)。

%w Number of waits: times that the program was context-switched voluntarily, for instance while waiting for

an I/O operation to complete.

#:等待的次数,该项目被自愿交换上下文,例如在等待I / O操作完成。

I/O

%I Number of file system inputs by the process. #一些文件系统输入的过程。

%O Number of file system outputs by the process. #一些文件系统输出的过程。

%r Number of socket messages received by the process. #套接字接收到的消息的过程。

%s Number of socket messages sent by the process. #套接字发送的消息数量的过程。

%k Number of signals delivered to the process. #数量的信号传递过程。

%C (Not in tcsh.) Name and command line arguments of the command being timed.

#(不是在tcsh。)名称和命令的命令行参数被计时。

%x (Not in tcsh.) Exit status of the command.

#(不是在tcsh。)命令的退出状态。

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.

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 or make 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.

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time命令小结

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