The SED of shell programming

SED command

Text Processing Three musketeers:
Grep,egrep,fgrep: Text Filter
Sed: Stream editor, in behavior units
awk: Text formatting tool, Report Builder

sed [OPTION] ... {Script-only-if-no-other-script} [File] ...

Common options:
-N: Do not print the line is not OK, output mode space content to the screen;
-e: Multi-point editing; Connect multiple commands at the same time; You can also use semicolons ";" Separated
-F: Specifies the script file and applies the script to the file;
The contents of the script file, one command per line;
Cat Sed.rules
S/this/that/g
/^$/d
Sed-f Sed.rules Sed.text
-R: Supports the use of extended regular expressions;
-I: Directly modify the original file, you can use the-i.bak parameters to back up the original file;
Sed–i.bak ' s/dog/cat/g ' pets

Address delimitation:
(1) Not to address: The full text of the processing;
(2) Single address:
#: Specify the first few lines;
/pattern/: Each row that is matched by this pattern;
(3) Address range:
#,#: The first few lines to the first few lines;
#,+#: The first few lines to + #行;
#,/pat1/: Lines to first match to PAT1;
/PAT1/,/PAT2/: The first match to the row of the PAT1 to the first match to the PAT2 line;
$: last line;
(4) Step forward: ~
N/A: all odd lines;
2~1: all even lines;

Edit command:
D: Delete
Sed ' 1,5d '/etc/fstab
P: Printing, must use the-n parameter;
Ifconfig | Sed-n ' 2p ' shows the second line
Sed ' 1~2p '/etc/fstab odd rows displayed 2 times
Sed-n ' 1~2p '/etc/fstab show only odd lines
Sed ' 1~2d '/etc/fstab show even lines
I\text: Insert Text "text" in front of line, support using \ n to implement multiline insertion;
Sed ' 3 i \new line '/etc/fstab inserting new lines in front of the third row
Sed ' 3 i \new line\nanother New line '/etc/fstab
A\text: Append text "text" after line, support using \ n to implement multiline append;
Sed ' 3 a \new line '/etc/fstab insert new lines after the third row
Sed '/uuid/a \new line '/etc/fstab inserting new lines after the row containing the UUID
C\text: Replace the matched line with the text "text" specified here, note that the whole line is replaced;
W: Saves the matched result to the specified position;
Sed-n '/^[^#]/p '/etc/fstab
Sed '/^[^#]/w/tmp/fstab.new '/etc/fstab
R: Read text from other files and insert matching line; file merge;
Sed ' 3 r/etc/issue '/etc/fstab
=: The line number is printed for the row to match;
Sed '/^uuid/= '/etc/fstab
!: conditional inversion;
Sed '/^[^#]/d '/etc/fstab delete lines not beginning with #
Sed '/^#/!d '/etc/fstab delete lines not beginning with #
Sed ' 5!d '/etc/fstab retains only line 5th (processing unmatched rows)
s///: Find replacement, its delimiter can be self-specified, commonly used are [email protected]@@,s## #等;
By default, only the content that matches the first time is replaced;
Sed ' s/line/line '
To match up to 2 per line, use/2
Sed ' S/LINE/LINE/2 '
Replace tag:
G: global substitution;
P: Shows the successful replacement line;
W: Save the result of the replacement successfully to the specified file;
&amp: Refers to the entire contents of the previous search;
The Find Replacement command adds # to the beginning of each line of the/tmp/functions file that begins with a white-space character;
:%[email protected]^[[:space:]]@#&@g
\ (\): Back reference, reference grouping, such as s/\ (love\) able/\1r,loveable replaced with lovers;

Practice:
1. Delete all whitespace characters at the beginning of the line beginning with whitespace characters in the/etc/prelink.conf.d/grub2.conf file;
Sed ' [email protected]^[[:space:]]\[email protected]@ '/etc/prelink.conf.d/grub2.conf

2. Delete all the white characters from the beginning of the line beginning with # in the/etc/fstab file and the # after # and #.
Sed ' [email protected]^#[[:space:]]*@@ '/etc/fstab

3, output an absolute path to SED, take out its directory;
echo "/var/log/messages" | Sed ' [Email protected][^/]\[email protected]@ '
echo "/var/log/messages" | Sed-r ' [Email protected][^/][email protected]@ '

4. Add # At the beginning of each line of/root/install.log;
Sed ' [email protected]^.*@#&@ '/root/install.log
Sed ' [email protected]^@#@ '/root/install.log

5. Add # to the beginning of the line in the/etc/fstab file that does not begin with #;
Sed '/^#/[email protected]*@#&@ '/etc/fstab (processing unmatched rows)
Sed '/^#/[email protected]^@#@ '/etc/fstab

6, the processing/etc/fstab path, uses the SED command to take out its directory name and the base name;
echo "/etc/fstab" | Sed ' [Email protected][^/]\[email protected]@ '
echo "/etc/fstab" | Sed ' [Email protected]^.*[/]@@ '

7. Using SED to remove the IPv4 address of the ifconfig command;
Ifconfig | Sed-n ' 2p ' | Tr-s "" | Cut-d ""-f3

8. Filter out the schema field of RPM package in/media/cdrom/packages directory, and count the number of each architecture;
LS *.rpm | Sed ' [email protected]*\.\ (. *\) \[email protected]\[email protected] ' | Sort | Uniq-c
LS *.rpm | Sed-r ' [email protected]*\. (. *) \[email protected]\[email protected] ' | Sort | Uniq-c
LS *.rpm | Sed-r ' [email protected]*\. (.*)\.. *@\[email protected] ' | Sort | Uniq-c
LS *.rpm | Rev | cut-d.-f2 | Rev | Sort | Uniq-c
Rev:reverse lines of a file or files. Turn each line in reverse order;

9, statistics a file which word repeats the most times;
Egrep-o "[[: alpha:]]+]/etc/init.d/functions | Sort | uniq-c | Sort-n
Sed ' [email protected][^[:alpha:]]@\[email protected] '/etc/init.d/functions | Sort | uniq-c | Sort-n


Advanced Editing Commands:
H: The content of the pattern space is covered in the holding space;
H: Append the contents of the pattern space to the holding space;
G: To cover the contents of the holding space in the pattern space;
G: Append the contents of the holding space to the pattern space;
x: Swap the content in the pattern space with the content in the hold space;
N: Overwrites the next line of the row to the pattern space, reads the next input line, and processes the new line with the next command;
N: Append the next line of the row to the pattern space to read;
D: Delete rows in the pattern space;
D: Delete all rows in multi-line mode space;

Example:
Sed-n ' n;p ' file: Shows even rows;
Sed ' 1! G;h;$!d ' file: Display the contents of files in reverse order;
Sed ' $!d ' file: Take out the last line;
Sed ' $! n;$! D ' file: two rows after removal;
Sed '/^$/d; G '/etc/fstab: Delete all existing blank lines, and then add a blank line after all the non-blank lines;
Sed ' n;d ' file: Displays odd lines;
Sed ' G ' file: Adds a blank line behind the original line;
Sed-n ' 1! g;h; $p ' file: Displays the contents of files in reverse order;

The SED of shell programming