A summary of common methods for Linux shell commands

Date
# Take the day before
date-d ' 1 days ago ' +%y-%m-%d

Order, E-Name, set function: (alias)
Alias Ll= ' Ls-al '

Some special values
$$: (for this shell PID)
$!: Get the process pid of the subprocess, for example the Nohup command can get the PID
$: (? On??? The WAN of the sash? quiff?
$#: Number of parameters

$@: Representing "$1″" $2″ "$3″" $4″ "
$*: On behalf of "$1c$2c$3c$4″", where c. Beech refers to 糇 compromise?/p>

Declare
The numerical calculation is to use Declare-i sum=100+12
You can also use sum=$ ((100+12)) to calculate
[Root@www ~]# declare [-AIXR] Variable
????? /> BR-A: ⑨ Yan Ting? Variable's?? Knife, X-Guillotine, column (array)
-I: ⑨ Yan ting? Variable's?? A knife? x 檎?? Bottom (integer) type
-X: Usage? Export one cherry ⑨ Yan Xian variable?? The BR/>-r: ⒆?? Zhai O made? ReadOnly Type,??? Block 豢 kill Huan?? Jes, unset.

Array
var[1]= "Small min"
echo $ (var[1])

Delete/Replace character
echo ${path#/usr*:} #从前到后开始删除掉第一个符合条件的字符
echo ${path##/usr*:} #从前到后开始删除掉所有符合条件的字符
Or you can start at the back and replace the # number with the%
Echo ${PATH/USR/USR} #替换
Echo ${PATH//USR/USR} #替换所有

&& and | |
You can string together multiple commands, such as
ls./test/| | mkdir./test/#如果目录不存在, creating a

Judge
Note spaces must have [-e ' xxx '] when using brackets

Grammar

If ["$name" = = "Fatkun"]; Then
echo "hi! Fatkun "
elif [...]; Then
echo "..."
Else
echo "..."
Fi

What is the meaning of "y"?
1. In a??? N-Name "n-case" sentence? TEST-E filename Indicates whether there is
-e? "? N name "Does it exist?" Common
-F? "? N name "exists and?? n Case (file)? Common
-d? "? N name "Does it exist and is it a compliment?" (directory)? Common
B? "? N name "exists and is Ligularia?" Block device?
-C? "? N name "exists and is Ligularia?" Character device?
-S? "? N name "exists and is Ligularia?" The Socket? n case?
-P? "? N name "exists and is Ligularia?" FIFO (pipe)? n case?
-l? "? N name "exists and is Ligularia????? N?
2. In the case of n? Y, such as test-r filename, can you say no (but root ung s hin??)
-r?? Y?? n names exist and have a "can?" ?
W?? Y?? N Name exists and has "can??" ?
X?? Y?? n names exist and have a "can?"
-U?? Y?? Does n name exist and have "SUID"? Nuo yu
G?? Y?? Does n name exist and have "SGID"? Nuo yu
K?? Y?? Does n name exist and has "Sticky bit"? Nuo Yu
-S?? Y?? Does n name exist and Luo? n case "?
3.???? n the ratio of the case, such as: Test file1-nt file2
-nt (newer than) sentence? Whether File1 is newer than file2
-ot (older than) sentence? is file1 more than file2?
-ef sentence? File1? File2 is enshrined? n case, can be used in the sentence? Hard Link's decision. The main idea is to judge,???? Does n case all point to the same?? Inode Mile!
4.??? The judgment of N1-eq G, such as test N2
-eq?? Andy Sigh (equal)
-ne?? Withstand bad (not equal)
-GT N1 greater than N2 (greater than)
-lt N1 less than N2 (less than)
-ge N1 is larger than N2 (greater than or equal)
-le N1 is less than equal to N2 (less than or equal)
5. The material of the judgment string
Test-z string Determines whether the string is? 0? What if string? T? True
Test-n string to determine if the string is not? 0? What if string? T? False
?:-N can also be omitted
Test STR1 = str2 determine if str1 is equal to str2, and if so, t back? True
Test str1!= str2 determine if str1 is not equal to str2, if equivalent, t back? False
6. L-piece judgment, for example: Test-r filename-a-x filename
-A (and)??? R and R set up! For example Test-r file-a-x file,?t file with R? X? r, just back? True
-O (OR)??? R any one?? Was founded! For example, Test-r file-o-x file,?t file has R or X-r, you can go back? True
! The reverse phase?? B, like test! -X file,? File does not have X-r, back? True

Case syntax
Case $?? Have? Q in <==?? Word? Case,? The dam is embroidered with X-word?
"The first????? Hot quot; <== per????? Hot-ㄗh is surrounded by angry? P-word? t Tangyue ±ㄌ? )
Program Segment
;; <== per???? E. End use????? The points?? The Kip!
"The second????? Hot quot;
Program Segment
;;
*) <== last????? Jedi?? * 泶 硭 Peacemaker lu liling?? br/> does not contain the first????? Hot Chang C second????? Hot 莸 Sodium lu Liling, sash, br/> Exit 1
;;
Esac <== Most of the case? Tail! "Anti-????" Think about it!
While syntax
While [condition] <== is enclosed in the?? Que?? B is a fast sulphon br/> Do <==do is a circle?
Program paragraph
The done <==done is a circle?
For...do...done syntax
For Var in con1 con2 Con3 ...
Todo
Program Segment
Done
For ((i=1;i<100;i++));d o
Echo $i
Done
Replacement of soft chain
LN-SNF./hive-0.7.1/hive

Use grep and Gawk,xargs to kill
Xargs will turn each row of gawk into a kill parameter, such as Kill 1 2 3

Grep-v is excluded

Ps-ef|grep scott|grep-v Grep|gawk {' Print $1′}|xargs kill

SED command replaces text
Sed-i "s/oldstring/newstring/g" ' grep oldstring-l yourdir ' #在原文件修改
Sed "s/oldstring/newstring/g" file >file.new # output to other files
Tar
Tar--exclude=./xxx/cache--exclude=*/log/*-cvzf xxx_ ' date +%y-%m-%d_%h_%m '. tar.gz

Get Machine IP

/sbin/ifconfig-a|grep inet|grep-v 127.0.0.1|grep-v Inet6|awk ' {print $} ' |tr-d ' addr: '