Common commands and syntax for Grep,awk and SED

Common command syntax for grep

1. Double quote quotes and single quote references
when you enter a string parameter in the G r e P command, it is best to enclose it in double quotation marks. For example: "M y s t r i n g". There are two reasons for this, one is to avoid being misunderstood as the S H e l command, and the second is to find a string consisting of multiple words, for example: "Jet Plane", if it is not enclosed in double quotation marks, then the word p l a n e will be mistaken for a file, the query result will return "file does not exist" error 。 You should also use double quotes when calling variables, such as: G R E P "$ M Y VA r" file name, if not, no result will be returned. Single quotes should be used when calling pattern matching. [[email protected]]# echo ' grep 123 111.txt ' (#注意是反单引号)

2. The commonly used grep options are:
-C outputs only the count of matching rows.
- I is case-insensitive (only for single-character).
-H does not display a file name when querying multiple files.
-L Only output file names that contain matching characters when querying multiple files.
-n Displays matching lines and line numbers.
-S does not display error messages that do not exist or have no matching text.
-V Displays all lines that do not contain matching text.

3. Special--Query in multiple files
$ grep "Sort" *.doc (Find string "s O r T" in #在当前目录下所有. D o C file)
$ grep "Sort It" * (#或在所有文件中查询单词 "sort It")
all of the following examples refer to querying in a single file

4. Row matching
$ grep-c "48″DATA.F
$4 (#g r e P Returns the number 4, meaning that there are 4 rows that contain the string "4 8". )
$ grep "48″DATA.F (#显示包含" 4 8 "string of 4 lines of text)

5. Displays the number of rows that satisfy the matching pattern:
[email protected] oid2000]# grep-n 1234 111.txt
1:1234
3:1234ab

6. Exact Match
[[email protected] oid2000]# grep "1234\>" 111.txt
1234

7. Query for empty rows, and query for rows that begin or end with a condition.
use a combination of ^ and $ to query for blank lines. Use the-n parameter to display the actual number of rows
[[email protected] oid2000]# grep-n "^$" 111.txt (return result 2: #说明第二行是空行)
[email protected] oid2000]# grep-n "^ABC" 111.txt (#查询以abc开头的行)
[email protected] oid2000]# grep-n "abc$" 111.txt (#查询以abc结尾的行)

8. Match Special characters and query for characters that have special meanings, such as $. ' "* [] ^ | \ + ? , you must add \ before a specific character.
[[email protected] oid2000]# grep "\." 111.txt (#在111. txt in the query contains "." of all rows)
[[email protected] oid2000]# grep "my\.conf" 111.txt (#查询有文件名my. c o n f lines)

9. Querying the directory
[email protected] oid2000]# ls–l |grep "^d" (#如果要查询目录列表中的目录)
[email protected] oid2000]# ls–l |grep "^d[d]" (#在一个目录中查询不包含目录的所有文件)
[email protected]]# ls–l |grpe "^d.....x. X "(#查询其他用户和用户组成员有可执行权限的目录集合)

10. Exclude Yourself
ps-ef|grep telnet | grep-v grep (Extracts the "telnet" process in the displayed process; and discards the grep process in PS)
Common command syntax for awk
The awk Command specializes in formatting messages or extracting packets from a large text file, which is the basic syntax of the command
awk [-F Filed-separator] "commands" Input-file (s)
[-F-field delimiter] is optional, a W K uses a space as the default domain delimiter, if the file to be processed with a colon as the partition domain (such as the passwd file), then in the processing time to specify the Awk–f:command input-file (s)

1.1 fields and records
when a W K executes, its browse domain is marked as $1,$ 2 ... $ n. This method is called the domain identifier. With $1, $3 refers to the 1th and 3rd fields, and note that the fields are delimited by commas. If you want to print all fields of a record with 5 fields, you do not have to specify $1, $2, $3, $4, $5, and you can use $0, which means all domains.

1.2 Saving awk output
$ Awk ' {print $} ' input-files > Out-files (#重定向保存输出)
$ Awk ' {print $} ' input-files | tee out-files (#使用t e-e command, output to a file while output to the screen)

1.3 Examples of commonly used awk commands
[email protected]/]# awk ' $ ~/user/'/etc/passwd (#如果某域含有user就将该行打印出来)
rpc:x:32:32:portmapper RPC User:/:/sbin/nologin
rpcuser:x:29:29:rpc Service User:/var/lib/nfs:/sbin/nologin
[email protected]/]# awk '/user/'/etc/passwd (#同上)
[email protected]/]# awk-f: ' {if ($/user/) print $} '/etc/passwd (#如第五域有user则输出该行)
rpc:x:32:32:portmapper RPC User:/:/sbin/nologin
[[email protected]/]# ifconfig | awk '/inet/{print "(#从ifconfig的输出中抽取含inet的行并打印第二域)
[[email protected]/]# ifconfig | awk '/inet/{print $} ' | awk-f: ' {print $} ' (#在上面的基础上再抽取, this command allows you to get the IP address of the machine directly)

Common command syntax for sed

SED is a non-interactive text flow editor. It edits the text copy of the exported file or standard input.

1. Matching of rows
[[email protected]/]# sed-n ' 2p '/etc/passwd print out line 2nd
[[email protected]/]# sed-n ' 1,3p '/etc/passwd print out lines 1th to 3rd
[[email protected]/]# sed-n ' $p '/etc/passwd print out the last line
[[email protected]/]# sed-n '/user/' p/etc/passwd print out the line containing the user
rpc:x:32:32:portmapper RPC User:/:/sbin/nologin
rpcuser:x:29:29:rpc Service User:/var/lib/nfs:/sbin/nologin
[[email protected]/]# sed-n '/\$/' p/etc/passwd print out a line containing $ metacharacters, $ meaning the last line

2. Inserting text and additional text (inserting new lines)
[[email protected]/]# sed-n '/ftp/p '/etc/passwd print out the line with FTP
ftp:x:14:50:ftp User:/var/ftp:/sbin/nologin
[[email protected]/]# sed '/ftp/a\ 456′/etc/passwd insert a new row after the line containing the FTP with the contents 456
[[email protected]/]# sed '/ftp/i\ 123′/etc/passwd a new row in front of the line containing the FTP, the content is 123
[[email protected]/]# sed '/ftp/i\ ' 123″ '/etc/passwd insert a new line in front of the line containing the FTP, in the "123″
[[email protected]/]# sed ' 5 a\ 123′/etc/passwd insert a new row after line 5th with the contents 123
[[email protected]/]# sed ' 5 i\ "12345" '/etc/passwd insert a new line before line 5th with the content "12345"

3. Delete text
[[email protected]/]# sed ' 1d '/etc/passwd delete line 1th
[[email protected]/]# sed ' 1,3d '/etc/passwd delete line 1th to 3rd
[[email protected]/]# sed '/user/d '/etc/passwd delete line with user

4. Replace text, replace command replaces the specified pattern with the replacement mode, in the form:
[a D D r e s S [, address]] S/pattern-to-find/replacement-pattern/[g p w N]
[[email protected]/]# sed ' s/user/user/'/etc/passwd replace the 1th user with User,g to indicate a global replacement
[[email protected]/]# sed ' s/user/user/g '/etc/passwd replace all user with user
[[email protected]/]# sed ' s/user/#user/'/etc/passwd replace 1th user with #user, e.g. for shielding effect
[[email protected]/]# sed ' s/user//'/etc/passwd replace the 1th user with an empty
[[email protected]/]# sed ' s/user/&11111111111111/'/etc/passwd if you want to attach or modify a long string, you can use the (&) command,& command to save the discovery mode in order to recall it, and then put it in the replacement string, here is the & put in front
[[email protected]/]# sed ' s/user/11111111111111&/'/etc/passwd here is to put & back

5. Quick Line Command
here are some line command sets. ([] denotes a space, [] denotes t a b key)
' s/\. $//G ' delete ends with a period line
'-e/abcd/d ' delete the row containing a B c D
' s/[] [] [] */[]/G ' Remove one to the sky, with a space instead
' s/^ [] [] *//G ' Delete line beginning space
' s/\. [] [] */[]/g ' Delete period followed by two or more spaces, replaced by a space
'/^ $/d ' Delete empty lines
' s/^.//G ' Delete the first character
' S/col \(...\)//g' Delete the three letters immediately following C O l
' s/^ \///G ' Remove the first \ from the path
' s/[]/[]//G ' Remove all spaces and replace with T a B key
' S/^ []//G ' Delete all t a b keys at the beginning of the line
' s/[] *//G ' Remove all t a b keys
If you use S e d to filter the file, it is best to divide the problem into steps, step-wise, and edge-test results.
experience tells us that this is the most effective way to perform a complex task.
                                                        

Common commands and syntax for Grep,awk and SED