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分享User CPU , System CPU, Clock time什么区别？
在看unix环境高级编程时，Figure 3.5中列出了程序在不同情况下的执行时间，不明白其中各列代表什么含义：
1. Use CPU(seconds) 2. System CPU(seconds) 3. Clock CPU(seconds) 4.#loops
希望高人指点
1. Use CPU(seconds) 2. System CPU(seconds) 3. Clock CPU(seconds) 4.#loops
希望高人指点
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zhangxichao 2008-10-26
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blf0 2008-10-26
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可以参见 TIME 手册
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 output 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)).
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 sufficient 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 for-
matting 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 nonzero value (1-125) if something else went wrong.
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 output 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)).
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 sufficient 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 for-
matting 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 nonzero value (1-125) if something else went wrong.
