1. Description
Application of problem analysis and there are a lot of command, generally a combination of the use, under today focuses on:
(1) top command, view real-time server resource usage, Explorer-like under windows;
(2) tail command to view the log in real-time refresh command.
2. top command
top command is commonly used under Linux performance analysis tools, it can display real-time system resource usage status of each process.
2.1 Command Usage
top //默认每隔5秒，显示所有进程的资源占用情况
top -d 2 //每隔2秒，显示所有进程的资源占用情况
top -c //每隔5秒，显示所有进程的资源占用情况，-c重点是能看到命令行参数名称（比如java项目，不加-c的话只有java，增加-c的话，能看到具体执行参数，i'm 软件老王）2.2 top the displayed information
(1) The first line is not to say, mean nothing;
(2) the second line shows the process of summary information, including:
total 进程总数
running 正在运行的进程数
sleeping 睡眠的进程数
stopped 停止的进程数
zombie 僵尸进程数(3) the third line, shows the use of cpu, wherein:
0.2% us 用户空间占用CPU百分比
0.2% sy 内核空间占用CPU百分比
0.0% ni 用户进程空间内改变过优先级的进程占用CPU百分比
99.6% id 空闲CPU百分比
0.0% wa 等待输入输出的CPU时间百分比
0.0%hi：硬件CPU中断占用百分比
0.0%si：软中断占用百分比
0.0%st：虚拟机占用百分比Note: You can press "1", the third row can be expanded (for example, 4 cpu launched four lines) in the top command to see each cpu accounting situation.
(4) The fourth and fifth lines, shows the memory usage, wherein:
Mem:
total 物理内存总量
free 空闲内存总量
used 使用的物理内存总量
buffer 用作内核缓存的内存量
Swap:
total 交换区总量
free 空闲交换区总量
used 使用的交换区总量
avail Mem 有效内存(5) the sixth row, shows the specific users and processes cpu and memory use cases, including:
PID 进程id
USER Real user name
PR 优先级
NI nice值。负值表示高优先级，正值表示低优先级
VIRT 进程使用的虚拟内存总量，单位kb。VIRT=SWAP+RES
RES 进程使用的、未被换出的物理内存大小，单位kb。RES=CODE+DATA
SHR 共享内存大小，单位kb
S 进程状态(D=不可中断的睡眠状态,R=运行,S=睡眠,T=跟踪/停止,Z=僵尸进程)
%CPU 上次更新到现在的CPU时间占用百分比
%MEM 进程使用的物理内存百分比
TIME 进程使用的CPU时间总计，单位秒
COMMAND 命令名/命令行Special Note: Note that the% cpu cpu third row with a sixth row of a difference.
Which cpu third line (%) represents the average of all the user processes throughout the cpu, because each occupies a percentage of the core, so by comparison with a reference to count the average sense, but the sixth line of the display% CPU is a nuclear process takes a percentage, rather than the percentage of the total cpu (4-core), and sometimes may be greater than 100, it is because the process enables multi-threaded occupies multiple core (i'm Pharaoh software), so sometimes we look at the time worth more than 100%, but will not exceed the total number of cores * 100.
3. tail view real-time log command
3.1 real-time view the log file
(1) Description: When you need to locate or view the problem, the need for real-time tracking logs.
(2) Command Usage
tail -f test.log(3) tail command parsing
-f 循环读取
-q 不显示处理信息
-v 显示详细的处理信息
-c<数目> 显示的字节数
-n<行数> 显示行数
–pid=PID 与-f合用,表示在进程ID,PID死掉之后结束.
-q, –quiet, –silent 从不输出给出文件名的首部
-s, –sleep-interval=S 与-f合用,表示在每次反复的间隔休眠S秒 3.2 Empty file
(1) Description: Sometimes the log file contents or a little more, is not convenient to view, needs to be emptied, you can use the copy and then deleted, but a bit of trouble, you can use echo directly emptied.
(2) Command Usage
echo > nohup.outIntermediate spaces can not be
(3) echo usage examples
a. printed to the console
echo I am 软件老王
echo "I am 软件老王"b. Print to file
touch test.txt
echo 软件老王 > test.txtc. additional content to file
echo 是帅哥 >> test.txtI'm "Software Pharaoh," I felt that if I may, to focus the next chant, subsequent updates seconds to know! Welcome forum, No. namesake public message exchange!