Skills accumulated in Linux over the past five years (3)-system (II)

Skills accumulated in Linux over the past five years (3) -- skills accumulated in Linux over the past five years (2) -- skills accumulated in the system (I) http://www.bkjia.com/ OS /201303/193589.html this article mainly introduces some of the Linux system skills. Author of JH Gao <gaopenghigh@gmail.com> from the beginning of Linux has been in touch with the present for five years, and everyone is the same, it is indispensable to toss. Once in a while, I will record the method. Now I will briefly summarize it. The command functions of www.2cto.com can be found through man. I only list what I think is commonly used. 1. in bash, the $ related parameter Shell code $0 indicates the current file name $ *. All parameters are separated by spaces to form a string $ @-. All parameters are separated by spaces to form a string combination. Different from $ *, when being referenced by "", "$ *" is a string, "$ @" contains multiple strings $ #-number of parameters passed to the process $? -The execution result of the previous command. If no error occurs, the value 0 $-PID 2 of this command. bash technique, which combines the content of a variable into the name EXAMPLE of another variable: shell code A_ B _C_D = "something" t1 = "B" t2 = "_ D" eval echo \ $ A _ $ {t1} _ C $ {t2}; 3. thinkPad X220 setting in Ubuntu (12.04, 12.10, set the sensitivity and speed respectively. Shell code echo-n 225>/sys/devices/platform/i8042/serio1/serio2/sensiti1_echo-n 115>/sys/devices/platform/i8042/ serio1/serio2/speed 4. back up the Main Boot Sector (bootsector) if the Startup File is corrupted, you can restore the Main Boot Sector to view the repair: Back up Shell code d D if =/dev/hda of = bootsector. img bs = 512 count = 1 restore Shell code dd if = bootsector. the above two steps of img of =/dev/hda only restored the primary boot sector. It is likely that all the content in/boot must be restored before it can be started normally, you can also back up the files under/boot. 5. bash command line Input tips: use Ctrl + R to search for previously used commands use Ctrl + W to delete the current single-time use Ctrl + U to delete the current row 6. xargs is very powerful. You can use-l {} to specify the parameter location: EXAMPLE Shell code cat hosts | xargs-I {} ssh root @ {} hostname 7. write a safe bash Script: set-e. When an error occurs, the script will exit set-u. When bash finds that there are initialization variables, it will exit. For more information, see: write a robust Bash script 8. tar package the files listed in the specified list: Shell code cat yourlist. lst/etc/fstab/home/admin/bin/somefile. sh/home/mysql/somefile... tar cvzf xxx.tar.gz-T yourlist. lst 9. specify a DNS server to query domain names Record the Shell code dig @ 8.8.8.8 www.google.com 10. the most important parameters of the sort command are-k and-s: Shell code-s, -- stable stabilize sort by disabling last-resort comparison stable. EXAMPLE Shell code $ cat a.txt a a B B $ sort-f a.txt a A B B $ sort-f-s a.txt a a B B in the EXAMPLE,-f indicates not case sensitive, -s indicates that the sequence depends on the sequence Shell code of the original file-k, -- key = POS1 [, POS2] start a key at POS1 (origin 1 ), end it at POS2 (default end of line ). therefore, we should write the command in the second column: Shell code sort-k1, 1