python中的eval函数使用实例

top 命令 是每个人都在使用的用于 监控 Linux 系统性能 的最好的命令。你可能已经知道 top 命令的绝大部分操作，除了很少的几个操作，如果我没错的话，批处理模式就是其中之一。

大部分的脚本编写者和开发人员都知道这个，因为这个操作主要就是用来编写脚本。

如果你不了解这个，不用担心，我们将在这里介绍它。

什么是 top 命令的批处理模式

批处理模式允许你将 top 命令的输出发送至其他程序或者文件中。

在这个模式中，top 命令将不会接收输入并且持续运行，直到迭代次数达到你用 -n 选项指定的次数为止。

如果你想解决 Linux 服务器上的任何性能问题，你需要正确的 理解 top 命令的输出。

1) 如何在批处理模式下运行 top 命令

默认地，top 命令按照 CPU 的使用率来排序输出结果，所以当你在批处理模式中运行以下命令时，它会执行同样的操作并打印前 35 行：

# top -bc | head -35
top - 06:41:14 up 8 days, 20:24, 1 user, load average: 0.87, 0.77, 0.81
Tasks: 139 total,  1 running, 136 sleeping,  0 stopped,  2 zombie
%Cpu(s): 0.0 us, 3.2 sy, 0.0 ni, 96.8 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
KiB Mem : 3880940 total, 1595932 free,  886736 used, 1398272 buff/cache
KiB Swap: 1048572 total,  514640 free,  533932 used. 2648472 avail Mem
PID USER   PR NI  VIRT  RES  SHR S %CPU %MEM   TIME+ COMMAND
   1 root   20  0 191144  2800  1596 S  0.0 0.1  5:43.63 /usr/lib/systemd/systemd --switched-root --system --deserialize 22
   2 root   20  0    0   0   0 S  0.0 0.0  0:00.32 [kthreadd]
   3 root   20  0    0   0   0 S  0.0 0.0  0:28.10 [ksoftirqd/0]
   5 root    0 -20    0   0   0 S  0.0 0.0  0:00.00 [kworker/0:0H]
   7 root   rt  0    0   0   0 S  0.0 0.0  0:33.96 [migration/0]
   8 root   20  0    0   0   0 S  0.0 0.0  0:00.00 [rcu_bh]
   9 root   20  0    0   0   0 S  0.0 0.0 63:05.12 [rcu_sched]
  10 root    0 -20    0   0   0 S  0.0 0.0  0:00.00 [lru-add-drain]
  11 root   rt  0    0   0   0 S  0.0 0.0  0:08.79 [watchdog/0]
  12 root   rt  0    0   0   0 S  0.0 0.0  0:08.82 [watchdog/1]
  13 root   rt  0    0   0   0 S  0.0 0.0  0:44.27 [migration/1]
  14 root   20  0    0   0   0 S  0.0 0.0  1:22.45 [ksoftirqd/1]
  16 root    0 -20    0   0   0 S  0.0 0.0  0:00.00 [kworker/1:0H]
  18 root   20  0    0   0   0 S  0.0 0.0  0:00.01 [kdevtmpfs]
  19 root    0 -20    0   0   0 S  0.0 0.0  0:00.00 [netns]
  20 root   20  0    0   0   0 S  0.0 0.0  0:01.35 [khungtaskd]
  21 root    0 -20    0   0   0 S  0.0 0.0  0:00.02 [writeback]
  22 root    0 -20    0   0   0 S  0.0 0.0  0:00.00 [kintegrityd]
  23 root    0 -20    0   0   0 S  0.0 0.0  0:00.00 [bioset]
  24 root    0 -20    0   0   0 S  0.0 0.0  0:00.00 [kblockd]
  25 root    0 -20    0   0   0 S  0.0 0.0  0:00.00 [md]
  26 root    0 -20    0   0   0 S  0.0 0.0  0:00.00 [edac-poller]
  33 root   20  0    0   0   0 S  0.0 0.0  1:19.07 [kswapd0]
  34 root   25  5    0   0   0 S  0.0 0.0  0:00.00 [ksmd]
  35 root   39 19    0   0   0 S  0.0 0.0  0:12.80 [khugepaged]
  36 root    0 -20    0   0   0 S  0.0 0.0  0:00.00 [crypto]
  44 root    0 -20    0   0   0 S  0.0 0.0  0:00.00 [kthrotld]
  46 root    0 -20    0   0   0 S  0.0 0.0  0:00.00 [kmpath_rdacd]

2) 如何在批处理模式下运行 top 命令并按内存使用率排序结果

在批处理模式中运行以下命令按内存使用率对结果进行排序：

# top -bc -o +%MEM | head -n 20
top - 06:42:00 up 8 days, 20:25, 1 user, load average: 0.66, 0.74, 0.80
Tasks: 146 total,  1 running, 145 sleeping,  0 stopped,  0 zombie
%Cpu(s): 0.0 us, 0.0 sy, 0.0 ni,100.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
KiB Mem : 3880940 total, 1422044 free, 1059176 used, 1399720 buff/cache
KiB Swap: 1048572 total,  514640 free,  533932 used. 2475984 avail Mem
 PID USER   PR NI  VIRT  RES  SHR S %CPU %MEM   TIME+ COMMAND
 18105 mysql   20  0 1453900 156096  8816 S  0.0 4.0  2:12.98 /usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid
 1841 root   20  0 228980 107036  5360 S  0.0 2.8  0:05.56 /usr/local/cpanel/3rdparty/perl/528/bin/perl -T -w /usr/local/cpanel/3rdparty/bin/spamd --max-children=3 --max-spare=1 --allowed-ips=127.0.0.+
 4301 root   20  0 230208 104608  1816 S  0.0 2.7  0:03.77 spamd child
 8139 nobody  20  0 257000 27108  3408 S  0.0 0.7  0:00.04 /usr/sbin/httpd -k start
 7961 nobody  20  0 256988 26912  3160 S  0.0 0.7  0:00.05 /usr/sbin/httpd -k start
 8190 nobody  20  0 256976 26812  3140 S  0.0 0.7  0:00.05 /usr/sbin/httpd -k start
 8353 nobody  20  0 256976 26812  3144 S  0.0 0.7  0:00.04 /usr/sbin/httpd -k start
 8629 nobody  20  0 256856 26736  3108 S  0.0 0.7  0:00.02 /usr/sbin/httpd -k start
 8636 nobody  20  0 256856 26712  3100 S  0.0 0.7  0:00.03 /usr/sbin/httpd -k start
 8611 nobody  20  0 256844 25764  2228 S  0.0 0.7  0:00.01 /usr/sbin/httpd -k start
 8451 nobody  20  0 256844 25760  2220 S  0.0 0.7  0:00.04 /usr/sbin/httpd -k start
 8610 nobody  20  0 256844 25748  2224 S  0.0 0.7  0:00.01 /usr/sbin/httpd -k start
 8632 nobody  20  0 256844 25744  2216 S  0.0 0.7  0:00.03 /usr/sbin/httpd -k start

上面命令的详细信息：

-b：批处理模式选项

-c：打印运行中的进程的绝对路径

-o：指定进行排序的字段

head：输出文件的第一部分

-n：打印前 n 行

3) 如何在批处理模式下运行 top 命令并按照指定的用户进程对结果进行排序

如果你想要按照指定用户进程对结果进行排序请运行以下命令：

# top -bc -u mysql | head -n 10
top - 06:44:58 up 8 days, 20:27, 1 user, load average: 0.99, 0.87, 0.84
Tasks: 140 total,  1 running, 137 sleeping,  0 stopped,  2 zombie
%Cpu(s): 13.3 us, 3.3 sy, 0.0 ni, 83.3 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
KiB Mem : 3880940 total, 1589832 free,  885648 used, 1405460 buff/cache
KiB Swap: 1048572 total,  514640 free,  533932 used. 2649412 avail Mem
 PID USER   PR NI  VIRT  RES  SHR S %CPU %MEM   TIME+ COMMAND
 18105 mysql   20  0 1453900 156888  8816 S  0.0 4.0  2:16.42 /usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid

4) 如何在批处理模式下运行 top 命令并按照处理时间进行排序

在批处理模式中使用以下 top 命令按照处理时间对结果进行排序。这展示了任务从启动以来已使用的总 CPU 时间。

但是如果你想要检查一个进程在 Linux 上运行了多长时间请看接下来的文章：

检查 Linux 中进程运行时间的五种方法

# top -bc -o TIME+ | head -n 20
top - 06:45:56 up 8 days, 20:28, 1 user, load average: 0.56, 0.77, 0.81
Tasks: 148 total,  1 running, 146 sleeping,  0 stopped,  1 zombie
%Cpu(s): 0.0 us, 3.1 sy, 0.0 ni, 96.9 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
KiB Mem : 3880940 total, 1378664 free, 1094876 used, 1407400 buff/cache
KiB Swap: 1048572 total,  514640 free,  533932 used. 2440332 avail Mem
 PID USER   PR NI  VIRT  RES  SHR S %CPU %MEM   TIME+ COMMAND
   9 root   20  0    0   0   0 S  0.0 0.0 63:05.70 [rcu_sched]
  272 root   20  0    0   0   0 S  0.0 0.0 16:12.13 [xfsaild/vda1]
 3882 root   20  0 229832  6212  1220 S  0.0 0.2  9:00.84 /usr/sbin/httpd -k start
   1 root   20  0 191144  2800  1596 S  0.0 0.1  5:43.75 /usr/lib/systemd/systemd --switched-root --system --deserialize 22
 3761 root   20  0  68784  9820  2048 S  0.0 0.3  5:09.67 tailwatchd
 3529 root   20  0 404380  3472  2604 S  0.0 0.1  3:24.98 /usr/sbin/rsyslogd -n
 3520 root   20  0 574208  572  164 S  0.0 0.0  3:07.74 /usr/bin/python2 -Es /usr/sbin/tuned -l -P
  444 dbus   20  0  58444  1144  612 S  0.0 0.0  2:23.90 /usr/bin/dbus-daemon --system --address=systemd: --nofork --nopidfile --systemd-activation
 18105 mysql   20  0 1453900 157152  8816 S  0.0 4.0  2:17.29 /usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid
  249 root    0 -20    0   0   0 S  0.0 0.0  1:28.83 [kworker/0:1H]
  14 root   20  0    0   0   0 S  0.0 0.0  1:22.46 [ksoftirqd/1]
  33 root   20  0    0   0   0 S  0.0 0.0  1:19.07 [kswapd0]
  342 root   20  0  39472  2940  2752 S  0.0 0.1  1:18.17 /usr/lib/systemd/systemd-journald

5) 如何在批处理模式下运行 top 命令并将结果保存到文件中

如果出于解决问题的目的，你想要和别人分享 top 命令的输出，请使用以下命令重定向输出到文件中：

# top -bc | head -35 > top-report.txt
# cat top-report.txt
top - 06:47:11 up 8 days, 20:30, 1 user, load average: 0.67, 0.77, 0.81
Tasks: 133 total,  4 running, 129 sleeping,  0 stopped,  0 zombie
%Cpu(s): 59.4 us, 12.5 sy, 0.0 ni, 28.1 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
KiB Mem : 3880940 total, 1596268 free,  843284 used, 1441388 buff/cache
KiB Swap: 1048572 total,  514640 free,  533932 used. 2659084 avail Mem
 PID USER   PR NI  VIRT  RES  SHR S %CPU %MEM   TIME+ COMMAND
 9686 daygeekc 20  0 406132 62184 43448 R 94.1 1.6  0:00.34 /opt/cpanel/ea-php56/root/usr/bin/php-cgi
 9689 nobody  20  0 256588 24428  1184 S  5.9 0.6  0:00.01 /usr/sbin/httpd -k start
   1 root   20  0 191144  2800  1596 S  0.0 0.1  5:43.79 /usr/lib/systemd/systemd --switched-root --system --deserialize 22
   2 root   20  0    0   0   0 S  0.0 0.0  0:00.32 [kthreadd]
   3 root   20  0    0   0   0 S  0.0 0.0  0:28.11 [ksoftirqd/0]
   5 root    0 -20    0   0   0 S  0.0 0.0  0:00.00 [kworker/0:0H]
   7 root   rt  0    0   0   0 S  0.0 0.0  0:33.96 [migration/0]
   8 root   20  0    0   0   0 S  0.0 0.0  0:00.00 [rcu_bh]
   9 root   20  0    0   0   0 R  0.0 0.0 63:05.82 [rcu_sched]
  10 root    0 -20    0   0   0 S  0.0 0.0  0:00.00 [lru-add-drain]
  11 root   rt  0    0   0   0 S  0.0 0.0  0:08.79 [watchdog/0]
  12 root   rt  0    0   0   0 S  0.0 0.0  0:08.82 [watchdog/1]
  13 root   rt  0    0   0   0 S  0.0 0.0  0:44.28 [migration/1]
  14 root   20  0    0   0   0 S  0.0 0.0  1:22.46 [ksoftirqd/1]
  16 root    0 -20    0   0   0 S  0.0 0.0  0:00.00 [kworker/1:0H]
  18 root   20  0    0   0   0 S  0.0 0.0  0:00.01 [kdevtmpfs]
  19 root    0 -20    0   0   0 S  0.0 0.0  0:00.00 [netns]
  20 root   20  0    0   0   0 S  0.0 0.0  0:01.35 [khungtaskd]
  21 root    0 -20    0   0   0 S  0.0 0.0  0:00.02 [writeback]
  22 root    0 -20    0   0   0 S  0.0 0.0  0:00.00 [kintegrityd]
  23 root    0 -20    0   0   0 S  0.0 0.0  0:00.00 [bioset]
  24 root    0 -20    0   0   0 S  0.0 0.0  0:00.00 [kblockd]
  25 root    0 -20    0   0   0 S  0.0 0.0  0:00.00 [md]
  26 root    0 -20    0   0   0 S  0.0 0.0  0:00.00 [edac-poller]
  33 root   20  0    0   0   0 S  0.0 0.0  1:19.07 [kswapd0]
  34 root   25  5    0   0   0 S  0.0 0.0  0:00.00 [ksmd]
  35 root   39 19    0   0   0 S  0.0 0.0  0:12.80 [khugepaged]
  36 root    0 -20    0   0   0 S  0.0 0.0  0:00.00 [crypto]

如何按照指定字段对结果进行排序

在 top 命令的最新版本中， 按下 f 键进入字段管理界面。

要使用新字段进行排序， 请使用 up/down 箭头选择正确的选项，然后再按下 s 键进行排序。最后按 q 键退出此窗口。

Fields Management for window 1:Def, whose current sort field is %CPU
  Navigate with Up/Dn, Right selects for move then or Left commits,
  'd' or toggles display, 's' sets sort. Use 'q' or to end!
 PID   = Process Id       nsUTS  = UTS namespace Inode
 USER  = Effective User Name  LXC   = LXC container name
 PR   = Priority        RSan  = RES Anonymous (KiB)
 NI   = Nice Value       RSfd  = RES File-based (KiB)
 VIRT  = Virtual Image (KiB)  RSlk  = RES Locked (KiB)
 RES   = Resident Size (KiB)  RSsh  = RES Shared (KiB)
 SHR   = Shared Memory (KiB)  CGNAME = Control Group name
 S    = Process Status     NU   = Last Used NUMA node
 %CPU  = CPU Usage
 %MEM  = Memory Usage (RES)
 TIME+  = CPU Time, hundredths
 COMMAND = Command Name/Line
 PPID  = Parent Process pid
 UID   = Effective User Id
 RUID  = Real User Id
 RUSER  = Real User Name
 SUID  = Saved User Id
 SUSER  = Saved User Name
 GID   = Group Id
 GROUP  = Group Name
 PGRP  = Process Group Id
 TTY   = Controlling Tty
 TPGID  = Tty Process Grp Id
 SID   = Session Id
 nTH   = Number of Threads
 P    = Last Used Cpu (SMP)
 TIME  = CPU Time
 SWAP  = Swapped Size (KiB)
 CODE  = Code Size (KiB)
 DATA  = Data+Stack (KiB)
 nMaj  = Major Page Faults
 nMin  = Minor Page Faults
 nDRT  = Dirty Pages Count
 WCHAN  = Sleeping in Function
 Flags  = Task Flags
 CGROUPS = Control Groups
 SUPGIDS = Supp Groups IDs
 SUPGRPS = Supp Groups Names
 TGID  = Thread Group Id
 OOMa  = OOMEM Adjustment
 OOMs  = OOMEM Score current
 ENVIRON = Environment vars
 vMj   = Major Faults delta
 vMn   = Minor Faults delta
 USED  = Res+Swap Size (KiB)
 nsIPC  = IPC namespace Inode
 nsMNT  = MNT namespace Inode
 nsNET  = NET namespace Inode
 nsPID  = PID namespace Inode
 nsUSER = USER namespace Inode

对 top 命令的旧版本，请按 shift+f 或 shift+o 键进入字段管理界面进行排序。

要使用新字段进行排序，请选择相应的排序字段字母， 然后按下回车键排序。

Current Sort Field: N for window 1:Def
 Select sort field via field letter, type any other key to return
 a: PID    = Process Id
 b: PPID    = Parent Process Pid
 c: RUSER   = Real user name
 d: UID    = User Id
 e: USER    = User Name
 f: GROUP   = Group Name
 g: TTY    = Controlling Tty
 h: PR     = Priority
 i: NI     = Nice value
 j: P     = Last used cpu (SMP)
 k: %CPU    = CPU usage
 l: TIME    = CPU Time
 m: TIME+   = CPU Time, hundredths
* N: %MEM    = Memory usage (RES)
 o: VIRT    = Virtual Image (kb)
 p: SWAP    = Swapped size (kb)
 q: RES    = Resident size (kb)
 r: CODE    = Code size (kb)
 s: DATA    = Data+Stack size (kb)
 t: SHR    = Shared Mem size (kb)
 u: nFLT    = Page Fault count
 v: nDRT    = Dirty Pages count
 w: S     = Process Status
 x: COMMAND  = Command name/line
 y: WCHAN   = Sleeping in Function
 z: Flags   = Task Flags
 Note1:
  If a selected sort field can't be
  shown due to screen width or your
  field order, the '<' and '>' keys
  will be unavailable until a field
  within viewable range is chosen.
 Note2:
  Field sorting uses internal values,
  not those in column display. Thus,
  the TTY & WCHAN fields will violate
  strict ASCII collating sequence.
  (shame on you if WCHAN is chosen)

总结

以上所述是小编给大家介绍的批处理模式下运行 top 命令的方法,希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对我们网站的支持！

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