Text Three musketeers sed

My previous article introduced grep, and today I'll say a second sed, which is the abbreviation for Stream editor. In a Linux text file, the text is stored in a row, the display of many lines is actually because of the existence of a newline character, for example: The text is: Abc$def$ghi display is three line. Sed is a line editor that reads one line of text at a time and then, depending on our choices, synchronizes to the text. There's also an awk, called gawk (GNU awk) on Linux, which is a text formatting tool that we'll talk about in our next article.

Working mechanism: Each time a line of text is read into "pattern space", the processing is done in the mode space, and the processing result is output to the standard output device;

syntax: sed [OPTION] ... {Script} [Input-file] ...

-R: Supports extended regular expressions;

-N: Silent mode;

-E script1-e script2-e SCRIPT3: Specifies multiple scripts to run;

-f/path/to/script_file: Reads the script from the specified file and runs it;

-I: Directly modify the source file;

Address delimitation:

#: Specify line;

$: last line;

/regexp/: Any line that can be matched to by regexp; Sed '/^#/d '/etc/fstab #删除以井号开头的行

\%regexp%: Ibid., except for the regexp boundary symbol;

/regexp/| : Ignoring character case when matching;

\%regexp%| : Ignoring character case when matching;

Startline,endline:

#,/regexp/: Starting from # line, to the end of the line to which the first/regexp/is matched, all rows in the middle;

#,#

/regexp1/,/regexp2/: Starting from the first line that is matched to the/regexp1/, to the end of the line that is first matched to the/regexp2/, all rows in the middle;

#,+|-n: Starting with # lines, up to n rows down;

First~step: Specify the starting line, and the step size;

edit commands for sed

D: Delete rows in the pattern space; sed ' 1,2d '/etc/fstab

=: Display line number; the line number of the line beginning with sed '/^#/= '/etc/fstab #显示以 #

A \text: Additional text;sed '/^#/a \new line '/etc/fstab# to add the word "new" after the start of the well number

Sed ' 1a \new line\nsecond line\ntherid line ' #\n denotes newline characters

I \text: Insert text, support \ n implement multi-line insertion;

C \text: Replace the matching line with text; sed '/5,7/c \new txt ' #五到七行都替换成一个new txt

Sed '/^#/c \new txt '/etc/fstab# only the lines at the beginning of the well are replaced with new txt, not just one

P: Lines in print mode space; sed ' 5,7p '/etc/fstab#5-7 line content is displayed two times, using-N to meet our expectations

s/regexp/replacement/: Replace the content that is matched by regexp to replacement;

G: global substitution;

I: Case insensitive #sed ' s/^#//g '/etc/fstab

W/path/to/somefile: Save the specified content to the file specified by the/path/to/somefile path;

# sed ' 5,9w/tmp/test1.txt '/etc/fstab# writes 5-9 lines in Fstab to Test1.txt

R/path/from/somefile: Insert all the contents of another file at the specified location of the file, complete the file merge;

#sed ' 8r/etc/issue '/etc/fstab# to read the contents of the 8th line after issue and put it in front of the fstab.

Practice:

(1) Remove whitespace characters from the beginning of all lines in the/boot/grub/grub.conf file;

Sed ' s/^[[:space:]]\+//'/boot/grub/grub.conf

(2) Remove all # and white space characters from the beginning of the line at the beginning of #, followed by at least one white-space character, in the/etc/fstab file;

Sed ' s/^#[[:space:]]\+//'/etc/fstab

(3) Save the odd line of the/etc/fstab file as a/tmp/fstab.3;

Sed ' 1~2w/tmp/fstab.3 '/etc/fstab

(4) Echo a file path to the SED command, take out its base name, and further, take out its path name;

Base name: Echo "/etc/sysconfig/network-scripts/" | Sed ' [Email protected]^.*/\ ([^/]\+\]/\[email protected]\[email protected] '

Fetch path name: echo "/etc/sysconfig/network-scripts/" | Sed ' [Email protected][^/]\+/\[email protected]@ '

SED has not only a pattern space, but also a hold space, which helps SED to temporarily store something for later use.

Advanced Command:

H: Use the content of the pattern space to cover the content of keeping the space;

H: Append the contents of the pattern space to the content in the holding space;

G: Take its content from the hold space and overwrite it with the contents of the pattern space;

G: Take the content from the hold space and append it to the content in the pattern space;

X: Exchanging in the space of keeping and pattern;

N: Reads the next line from the matching row to the pattern space (overwrites the original content in the pattern space);

N: Reads the next line to the pattern space of the matched row, appended to the original content in the pattern space;

D: Delete the contents of the pattern space;

D: Delete the first row in multi-line mode space;

Note: Command function can be used! Reverse; semicolons can be used to separate scripts;

Example:

Sed ' G '/etc/issue: Adds a blank line behind each line in the file;

Sed ' $!d '/etc/fstab: Keep the last line;

Sed '/^$/d; G '/etc/issue: Ensure that the specified file has only one blank line behind each line;

Sed ' n;d '/etc/issue: reserved odd lines;

Sed-n ' 1! g;h; $p '/etc/issue: Full-text flashback display

Sed ' $! n;$! D '/etc/issue: Show last two lines

Text Three musketeers sed