Linux Note three: usage of grep and SED

grep [option] Pattern [FILE ...]

-I: Ignore case

--colour: Display in a highlighted color

-V: Show rows that are not matched to

-O: Displays only the string that is matched to

-E: Using extended regular expressions

-A #: including how many lines later

-B #: including how many lines ahead

-C #: including how many lines before and after

To extend the regular expression:

Character Matching:

.

[] such as: a-z,a-z

[^]

Number of matches:

*: Any time before the character

？ : matches the preceding character 1 or 0 times

+: Match the characters in front of it at least once

{M,n}:

Location anchoring:

^: Anchor the beginning of the line, any content after this character must appear at the beginning of the line

$: Anchor line end, any content after this character must appear at the beginning of the

^$: Blank Line

\< or \b: Anchor word, any character following it must appear as the first word

\> or \b: anchors the ending, any character preceding it must appear as the front of the word

Basic usage of SED;

Sed: line Editor

Sed ' addresscommand ' file ....

-N: Silent mode, content that is not in the default display mode space

-I: Modify the original file directly

-E script-e script: Multiple scripts can be executed simultaneously

-f/path/to/sed_script:

-r: Indicates the use of extended regular expressions

Command

D

P

A \string

I \string

R filename

W filename

s/pattern/string/modifier:

G: Global Substitution

I: Ignore case when finding

Sed exercises:

1, delete the/etc/grub.conf file in the beginning of the blank character;

Sed-r ' [email protected]^[[:space:]][email protected]@g '/etc/grub.conf

2. Replace the number in the "Id:3:initdefault:" line in the/etc/inittab file with 5;

Sed ' [email protected]\ (id:\) [0-9]\ (: initdefault:\) @\15\[email protected] '/etc/inittab

3, delete the blank line in the/etc/inittab file;

Sed '/^$/d '/etc/inittab

4. Delete the # number at the beginning of the/etc/inittab file;

Sed ' s/^#//g '/etc/inittab

5. Delete the # number at the beginning of a file, but require a white-space character after the # number;

Sed-r ' [email protected]^#[[:space:]][email protected]@g '/etc/inittab

6. Delete the white space characters in the file with the white space followed by the # in the convoy and #

Sed-r ' [Email protected]^[[:space:]]+#@@g '/etc/inittab

7. Take out a directory name for a file path;

echo "/ETC/RC.D" | Sed-r ' [email protected]^ (/.*/) [^/]+/[email protected]\[email protected] '

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Linux Note three: usage of grep and SED