什麼是Process
- 程序是一段指令的集合，被載入記憶體
- 使用 Numeric Process ID (PID) 識別程序
- UID, GID and SELinux context 決定 filesystem 存取
- Normally 繼承 from the 執行者
列出 Process
- View Process information with ps
[lcc09@localhost ~]$ ps --help
********* simple selection ********* ********* selection by list *********
-A 所有的程序 -C by command name
-N negate selection -G by real group ID (supports names)
-a all w/ tty except session leaders -U by real user ID (supports names)
-d all except session leaders -g by session OR by effective group name
-e all processes -p by process ID
T all processes on this terminal -s processes in the sessions given
a all w/ tty, including other users -t by tty
g OBSOLETE -- DO NOT USE -u by effective user ID (supports names)
r only running processes U processes for specified users
x 把包含不被ttys控制的程序都列出來
*********** output format ********** *********** long options ***********
-o,o user-defined -f full --Group --User --pid --cols --ppid
-j,j job control s signal --group --user --sid --rows --info
-O,O preloaded -o v virtual memory --cumulative --format --deselect
-l,l long u user-oriented --sort --tty --forest --version
-F extra full X registers --heading --no-heading --context
********* misc options *********
-V,V show version L list format codes f ASCII art forest
-m,m,-L,-T,H threads S children in sum -y change -l format
-M,Z security data c true command name -c scheduling class
-w,w wide output n numeric WCHAN,UID -H process hierarchy
- 常用的ps指令
[lcc09@localhost ~]$ ps ax
PID TTY STAT TIME COMMAND
1 ? Ss 0:02 init [5]
2 ? S 0:00 [migration/0]
3 ? SN 0:00 [ksoftirqd/0]
4 ? S 0:00 [watchdog/0]
5 ? S< 0:00 [events/0]
6 ? S< 0:00 [khelper]
7 ? S< 0:00 [kthread]
10 ? S< 0:00 [kblockd/0]
11 ? S< 0:00 [kacpid]
67 ? S< 0:00 [cqueue/0]
70 ? S< 0:00 [khubd]
72 ? S< 0:00 [kseriod]
134 ? S 0:00 [pdflush]
135 ? S 0:01 [pdflush]
136 ? S< 0:01 [kswapd0]
137 ? S< 0:00 [aio/0]
289 ? S< 0:00 [kpsmoused]
320 ? S< 0:00 [scsi_eh_0]
325 ? S< 0:00 [kmirrord]
330 ? S< 0:00 [ksnapd]
333 ? S< 0:03 [kjournald]
366 ? S< 0:00 [kauditd]
...(略)...
- Most flexible: ps options | other commands
ps axo comm,tty | grep ttyS0
- By 預先定義選項的: pgrep
- $ pgrep -U root
- $ pgrep -G student
- 練習
[lcc09@localhost ~]$ ps axo pid,comm | grep 'cups' 1948 cupsd 2464 eggcups [lcc09@localhost ~]$ pgrep cups 1948 2464
信號
- 信號是程序之間用來溝通的基礎方式
- Sent directly to processes, no user-interface required
- 程式會結合並注意著每個信號
- 有幾個較為特別的 Signals
- Signal 15, TERM (default) - 乾淨的終止程序
- Signal 9, KILL - 立即終止程序
- Signal 1, HUP - Re-read configuration files
- man 7 signal 可以得到完整的信號列表
送出信號給程序
- 送出 Signals to Processes
- 語法 By PID: kill [signal] pid ...
- 語法 By Name: killall [signal] comm ...
- 語法 By pattern: pkill [-signal] pattern
排成優先等級
- 排成的優先等級決定存取 CPU 的順序
- 排成決定在 process' nice 值
- 值的範圍從 -20 到 19 預設為 0
- 越低的值，有越高的的優先權
- 可以使用這些指令觀看 ps -o comm,nice
修改優先等級
- 修改排成優先等級
- Process's Nice values 可以被改變
- 當啟動一個 process
$ nice -n 5 command
- 啟動之後可以這樣修改
$ renice 5 PID
- 只有 root 能增減 nice values
[root@localhost ~]# renice -15 -p PID # PID is number
Interactive Process Management Tools
- CLI: top
- GUI: gnome-system-monitor
- Capabilities
- Display real-time process information
- Allow sorting, killing and re-nicing
工作任務控制
- Job Control
- 執行一個程序在背景工作
- 只要在指令後面加上一個「&」符號
- ex: gedit &
- 暫時停止一個執行中的程式
- Use Ctrl + Z or 或送出 signal 19 (STOP)
- 管理 背景程序 or 暫停程序 的 jobs
- 列出工作編號及名稱指令: jobs
- 轉移工作到背景繼續工作: bg [%jobnum]
- 轉移工作到前景繼續工作: fg [%jobnum]
- Send a signal: kill [-SIGNAL] [%jobnum]
- 範例：
[mtchang@localhost ~]$ top # 按下ctrl+z [1]+ Stopped top [mtchang@localhost ~]$ ps PID TTY TIME CMD 3590 pts/2 00:00:00 bash 3961 pts/2 00:00:00 top 3962 pts/2 00:00:00 ps [mtchang@localhost ~]$ ping 168.95.1.1 PING 168.95.1.1 (168.95.1.1) 56(84) bytes of data. 64 bytes from 168.95.1.1: icmp_seq=1 ttl=244 time=25.2 ms # 按下ctrl+z [2]+ Stopped ping 168.95.1.1 [mtchang@localhost ~]$ jobs [1]- Stopped top [2]+ Stopped ping 168.95.1.1 [mtchang@localhost ~]$ fg 2 # 叫出第二個工作 ping 168.95.1.1 64 bytes from 168.95.1.1: icmp_seq=2 ttl=244 time=155 ms 64 bytes from 168.95.1.1: icmp_seq=3 ttl=244 time=42.3 ms 64 bytes from 168.95.1.1: icmp_seq=4 ttl=244 time=63.9 ms 64 bytes from 168.95.1.1: icmp_seq=5 ttl=244 time=54.1 ms --- 168.95.1.1 ping statistics --- 5 packets transmitted, 5 received, 0% packet loss, time 35174ms rtt min/avg/max/mdev = 25.232/68.245/155.555/45.519 ms, pipe 2 [mtchang@localhost ~]$ jobs [1]+ Stopped top [mtchang@localhost ~]$ fg # 叫出順序中的第一個工作
nohup
- 讓程序不會因為父程序消失而結束，程序可以成為一個獨立的程序系統中工作。
- Usage: nohup COMMAND [ARG]... or: nohup OPTION
- Run COMMAND, ignoring hangup signals.
- 一般的wget作法，關掉視窗後，程式下載即消失。
$ wget ftp://ftp.isu.edu.tw/Linux/CentOS/5.0/isos-dvd/ CentOS-5.0-i386-bin-DVD.iso 2>wget.err >wget.doc & $ jobs [1]+ Running wget ftp://ftp.isu.edu.tw/Linux/CentOS/5.0/isos-dvd/ CentOS-5.0-i386-bin-DVD.iso 2>wget.err >wget.doc &
＊使用nohup
$ nohup wget ftp://ftp.isu.edu.tw/Linux/CentOS/5.0/isos-dvd/ CentOS-5.0-i386-bin-DVD.iso 2>wget.err >wget.doc & [2] 4096 $ ps auxw lcc09 4096 1.0 0.2 7884 1416 pts/1 S 20:50 0:00 wget ftp://ftp.isu.edu.tw/Linux/CentOS/5.0/isos-dvd/CentOS-5.0-i386 $ kill 4096 [lcc09@localhost:~bash: echo: write error: 中斷的系統呼叫 [2]+ 終止 nohup wget ftp://ftp.isu.edu.tw/Linux/CentOS/5.0/isos-dvd/ CentOS-5.0-i386-bin-DVD.iso 2>wget.err >wget.doc
- kill 傳送訊號範例
# 另開一個終端機畫面執行 top 指令 [root@server1 ~]# ps auxw ... root 4482 0.1 0.0 2188 1064 pts/10 S+ 19:38 0:00 top ... # 送訊號 19 給 4482 PID 的程序，以中斷信號 [root@server1 ~]# kill -19 4482 # 回到終端機畫面驗證
- 練習：請參考 033-ping網段檢測程式,將他修改為可以背景執行的方式，加速檢測的過程？
# 程式內容如下
[student@localhost sh]$ cat num.sh
#!/bin/bash
for n in {1..4};
do
echo 192.168.3.$n
echo "ping 192.168.3.$n -c1 1> /dev/null 2> /dev/null " | bash
echo "return value = $?"
done
# 程式可以執行,但是偵測速度很慢
[student@localhost sh]$ ./num.sh
192.168.3.1
return value = 0
192.168.3.2
return value = 1
192.168.3.3
return value = 1
192.168.3.4
return value = 1
排定程序執行
- 一次性的工作使用「at」
- 重複性的工作使用「crontab 」
| Create(建立指令) | at time | crontab -e |
|---|---|---|
| List(列出) | at -l | crontab -l |
| Details(詳細) | at -c jobnum | N/A |
| Remove(移除) | at -d jobnum | crontab -r |
| Edit | N/A | crontab -e |
- Non-redirected output is mailed to the user
- root can modify jobs for other users
- man at
NAME
at, batch, atq, atrm - queue, examine or delete jobs for
later execution
SYNOPSIS
at [-V] [-q queue] [-f file] [-mldbv] TIME
at [-V] [-q queue] [-f file] [-mldbv] -t time_arg
at -c job [job...]
atq [-V] [-q queue]
atrm [-V] job [job...]
batch [-V] [-q queue] [-f file] [-mv] [TIME]
- at範例
[mtchang@localhost ~]$ date 一 6月 4 23:32:01 CST 2007 [mtchang@localhost ~]$ at 23:34 at> echo 'test at ' > at.txt at># Ctrl-d end of line job 1 at 2007-06-04 23:34 [mtchang@localhost ~]$ at -l # list at jobs 1 2007-06-05 23:34 a mtchang [mtchang@localhost ~]$ date 一 6月 4 23:34:17 CST 2007 [mtchang@localhost ~]$ more at.txt test at
Crontab(定時排程)
- 系統的工作控制都排程在這個目錄 /etc/crontab
- /etc/cron.hourly/ Jobs are run on an hourly basis
- /etc/cron.daily/ Jobs are run on a daily basis
- /etc/cron.weekly/ Jobs are run on a weekly basis
- /etc/cron.monthly/ Jobs are run on a monthly basis
- 排程的工作可以針對單獨的使用者排定，這些工作儲存於 /var/spool/crontab
- 你可以使用crontab指令來編輯這些資料，指令用法如下：
- crontab -e Creates or edits jobs. For this, the vi editor is used.
- crontab file The specified file contains a list of jobs.
- crontab -l Displays current jobs.
- crontab -r Deletes all jobs.
- ex: user crontab
[lcc09@localhost ~]$ crontab -e 30 * * * * echo 'hello crontab' > /home/lcc09/crontab.txt [lcc09@localhost ~]$ cat crontab.txt hello crontab
- ex: root crontab , in every day 21:45 shutdown computer
# 需注意halt路徑,且halt關機並不會把電源也關閉,請改用shutdown or poweroff指令 45 21 * * * root /usr/sbin/halt
- Crontab檔案格式說明
- Entry consists of five space-delimited fields followed by a command line
- One entry per line, no limit to line length
- Fields are minute, hour, day of month, month, and day of week
- Comment lines begin with #
- See man 5 crontab for details
...(skip)....
field allowed values
----- --------------
minute 0-59
hour 0-23
day of month 1-31
month 1-12 (or names, see below)
day of week 0-7 (0 or 7 is Sun, or use names)
...(skip)....
- 常用的crontab 範例
EXAMPLE CRON FILE # use /bin/sh to run commands, no matter what /etc/passwd says SHELL=/bin/sh # mail any output to ‘paul’, no matter whose crontab this is MAILTO=paul # # run five minutes after midnight, every day 5 0 * * * $HOME/bin/daily.job >> $HOME/tmp/out 2>&1 # run at 2:15pm on the first of every month -- output mailed to paul 15 14 1 * * $HOME/bin/monthly # run at 10 pm on weekdays, annoy Joe 0 22 * * 1-5 mail -s "It’s 10pm" joe%Joe,%%Where are your kids?% 23 0-23/2 * * * echo "run 23 minutes after midn, 2am, 4am ..., everyday" 5 4 * * sun echo "run at 5 after 4 every sunday"
Grouping Commands
- Two ways to group commands:
- Compound: date; who | wc -l
- Commands run back-to-back
- Subshell: (date; who | wc -l) >> /tmp/trace
- All output is sent to a single STDOUT and STDERR
Exit Status
- 程序(Processes)回報完成程序後，會回報成功或失敗 with an exit status
- 0 是成功完成, 1-255 是失敗的錯誤訊息編號
- $? 儲存離開的狀態變數
- exit [num] terminates and sets status to num
- Example:
[mtchang@localhost ~]$ ping -c1 -W1 168.91.1.1 > /dev/null [mtchang@localhost ~]$ echo $? 1
Conditional Execution Operators
- Commands can be run conditionally based on exit status
- && represents conditional AND THEN
- || represents conditional OR ELSE
- 執行真值表，表列如下：
| 第一個指令執行 | 連接符號 | 第二指令執行狀態 |
|---|---|---|
| 成功 | ｜｜ | 不執行 |
| 失敗 | ｜｜ | 執行 |
| 成功 | ＆＆ | 執行 |
| 失敗 | ＆＆ | 不執行 |
- Examples:
[mtchang@localhost ~]$ grep -q no_user /etc/passwd || echo 'No such user' No such user # the second command runs if the first command fails # (it exits with an exit statis in th range of 1 ro 255) [mtchang@localhost ~]$ grep -q lcc09 /etc/passwd || echo 'No such user' [mtchang@localhost ~]$ grep -q lcc09 /etc/passwd && echo 'No such user' No such user
- ping 的範例
[student@localhost sh]$ \ echo "ping -c 3 192.168.3.1 >> ping_192.168.3.1.txt || echo 1 >\ ping_192.168.3.1.txt &" | bash [student@localhost sh]$ \ echo "ping -c 3 192.168.3.2 >> ping_192.168.3.2.txt || echo 1 >\ ping_192.168.3.2.txt &" | bash [student@localhost sh]$ tail ping_192.168.3.1.txt 3 packets transmitted, 3 received, 0% packet loss, time 1998ms rtt min/avg/max/mdev = 0.460/0.609/0.860/0.180 ms PING 192.168.3.1 (192.168.3.1) 56(84) bytes of data. 64 bytes from 192.168.3.1: icmp_seq=1 ttl=255 time=0.476 ms 64 bytes from 192.168.3.1: icmp_seq=2 ttl=255 time=0.466 ms 64 bytes from 192.168.3.1: icmp_seq=3 ttl=255 time=0.471 ms --- 192.168.3.1 ping statistics --- 3 packets transmitted, 3 received, 0% packet loss, time 1998ms rtt min/avg/max/mdev = 0.466/0.471/0.476/0.004 ms [student@localhost sh]$ tail ping_192.168.3.2.txt 1
test Command
- Evaluates boolean statements for use in conditional execution
- Returns 0 for true
- Returns 1 or more for false
- Examples in long form:
$ test "$A" = "$B" && echo "Strings are equal" $ test "$A" -eq "$B" && echo "Integers are equal"
- Examples in shorthand notation:
$ [ "$A" = "$B" ] && echo "Strings are equal" $ [ "$A" -eq "$B" ] && echo "Integers are equal"
[mtchang@localhost ~]$ test "$A" = "$B" && echo "Strings are equal" Strings are equal [mtchang@localhost ~]$ A='aaa' [mtchang@localhost ~]$ test "$A" = "$B" && echo "Strings are equal" [mtchang@localhost ~]$ B='aaa' [mtchang@localhost ~]$ test "$A" = "$B" && echo "Strings are equal" Strings are equal
- File Tests
- -b FILE FILE exists and is block special
- -c FILE FILE exists and is character special
- -d FILE FILE exists and is a directory
- -e FILE FILE exists
- -f FILE FILE exists and is a regular file
- -g FILE FILE exists and is set-group-ID
- -G FILE FILE exists and is owned by the effective group ID
- -h FILE FILE exists and is a symbolic link (same as -L)
- -k FILE FILE exists and has its sticky bit set
- -L FILE FILE exists and is a symbolic link (same as -h)
- -O FILE FILE exists and is owned by the effective user ID
- -p FILE FILE exists and is a named pipe
- -r FILE FILE exists and read permission is granted
- -s FILE FILE exists and has a size greater than zero
- -S FILE FILE exists and is a socket
- -t FD file descriptor FD is opened on a terminal
- -u FILE FILE exists and its set-user-ID bit is set
- -w FILE FILE exists and write permission is granted
- -x FILE FILE exists and execute (or search) permission is granted
Scripting: if Statements
- Execute instructions based on the exit status of a command
- 原始基本型的 if then fi
[lcc09@localhost ~]$ vi if.sh
#!/bin/bash
if ping -c1 -w2 168.95.1.1 &> /dev/null; then
echo 'Station1 is UP'
fi
[lcc09@localhost ~]$ chmod +x if.sh
[lcc09@localhost ~]$ ./if.sh
Station1 is UP
- 包含else if的敘述
[mtchang@localhost ~]$ vi if.sh
#!/bin/bash
if ping -c1 -w2 168.95.1.1 &> /dev/null; then
echo 'Station1 is UP'
elif grep "station1" ~/maintenance.txt &> /dev/null; then
echo 'Station1 is undergoing maintenance'
else
echo 'Station1 is unexpectedly DOWN!'
exit 1
fi
[mtchang@localhost ~]$ chmod +x if.sh
[mtchang@localhost ~]$ ./if.sh
Station1 is UP
- 延續上面的 ping 範例
[student@localhost sh]$ cat testping.sh
#!/bin/bash
if test $(tail -n 1 ping_192.168.3.1.txt|cut -d' ' -f1) = '1'; then
echo "192.168.3.1 is down"
else
echo "192.168.3.1 is up!!"
fi
[student@localhost sh]$ ./testping.sh
192.168.3.1 is up!!
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