Linux Basic Management--sed (Text Processing musketeers)

1. Introduction to SED

Sed, stream editor, line editor, because of its character syntax, is equivalent to a specialized language.

Sed is a stream editor that processes a single line of content at a time. When processing, the currently processed rows are stored in a temporary buffer called pattern space, followed by the SED command to process the contents of the buffer, and after processing is done, the contents of the buffer are sent to the screen. Then read the downstream line and execute the next loop. If you do not have a special command such as ' D ', it will empty the pattern space between the two loops, but will not empty the reserved space. This keeps repeating until the end of the file. The file content does not change unless you use redirection to store the output.

Function: Mainly used for automatic editing of one or more files, simplifying the repeated operation of files, writing conversion programs, etc.;

Reference:

Http://www.gnu.org/software/sed/manual/sed.html

2. How to use SED

2.1. Grammar

Grammar:

sed [option] ... ' Script ' Inputfile ...

Common options:

-N: does not output mode space content to the screen, that is, does not automatically print-e: Multipoint edit-f:/path/script_file: Read the edit script from the specified file-r: Support for using extended regular expressions-i.bak: Backing up files and editing them in situ

Script: ' Address command '.

2.2. Address Delimitation

(1) Not to address: The full text of the processing;

(2) Single address:

#: Specified line, $: Last line/pattern/: Each row that the pattern can match to

(3) Address range:

#,# #,+#/pat1/,/pat2/#,/pat1/

(4) ~: Step forward

Odd rows 2~2 even rows

2.3. Edit command

D: Delete the pattern space matching row, and immediately enable the next round of the loop p: print the current mode space content, append to the default output a [\]text: Append text after the specified line, support using \ n to implement multiline append I [\]text: Insert text in front of line C [\] Text: Replace behavior single-line or multiline text W/path/somefile: Save pattern matching line to specified file R/path/somefile: reads the text from the specified file to the line that matches the pattern space =: Prints the line number for the line in the pattern space!: Matching row inversion in pattern space

2.4. Replacement tool

s///: Find replacement, support use of other separators, [email protected]@@,s###

Replace tag:

G: In-line global substitution P: Display replace successful row w/path/to/somefile: Save the replacement row to a file

2.5. Sed edit tool, replacement tool example

Sed ' 2p '/etc/passwdsed–n ' 2p '/etc/passwdsed–n ' 1,4p '/etc/passwdsed–n '/root/p '/etc/passwdsed–n ' 2,/root/p '/etc/pa SSWD starts from 2 lines sed-n '/^$/= ' file displays blank line number sed–n–e '/^$/p ' –e '/^$/= ' filesed '/root/a\superman '/etc/passwd ' after line sed '/root/i\supe Rman '/etc/passwd line before sed '/root/c\superman '/etc/passwd instead of line

Sed '/^$/d ' filesed ' 1,10d ' filenl/etc/passwd | Sed ' 2,5d ' nl/etc/passwd | Sed ' 2a tea ' sed ' s/test/mytest/g ' examplesed–n ' s/root/&superman/p '/etc/passwd word after sed–n ' s/root/superman&/p '/ etc/passwd words before Sed-e ' s/dog/cat/'-e ' s/hi/lo/' petssed–i.bak ' s/dog/cat/g ' pets

2.6. Advanced editing commands

P: Print mode space start to \ n content and append to default output h: Overwrite content in pattern space to hold space H: Append content in pattern space to hold space G: Remove data from hold space to pattern space G: Append from Hold space to pattern space X: Swap the contents of the pattern space with the content in the Hold space N: reads the next line of matching rows to the pattern space N: reads the next line of the matched rows to the pattern space D: Delete the row in the pattern space D: If the pattern space contains a newline character, delete until the first The line breaks the text in the pattern space and does not read the new input line, but uses the composition's pattern space to restart the loop. If the pattern space does not contain a newline character, the normal new loop is started as if the D command was emitted

Examples of sed:

Sed-n ' n;p ' FILE sed ' 1! G;h;$!d ' FILE sed ' n;d ' FILE sed ' $! n;$! D ' file sed ' $!d ' file sed ' g ' file sed ' g ' file sed '/^$/d; G ' file sed ' n;d ' file Sed-n ' 1! g;h; $p ' FILE

Linux Basic Management--sed (Text Processing musketeers)