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Xiaobian to share with you how Shell script to achieve find and replace, I believe most people do not know how, so share this article for your reference, I hope you have a lot of harvest after reading this article, let us go to understand it together!

3.1 find text

grep: Basic regular expressions (BRE) defined using POSIX.

egrep: Use extended regular expressions (ERE).

Fgrep: Fast grep. Use optimized algorithms to match fixed strings instead of regular expressions.

The 1992 POSIX standard integrates these three revisions into a single grep program.

$ who | grep -F austen

Use the-F option to find fixed strings. In fact, as long as the matching pattern does not contain meta characters of regular expressions,

The grep default behavior pattern is equivalent to using-F.

3.2.6 Substitution in Text Files

In general, the correct program to perform text substitution is the sed-stream editor.

sed 's/:.*// ' /etc/passwd |Delete everything after the first colon

sort -u Sort lists and remove duplicates

Any displayable character can be used as a delimiter.

The code is as follows:

sed 's;/home/tolstoy/;/home/lt/;'

sed 's/\\/\\/g'

With the-e and-f options, you can replace multiple sed's at once without having to string them through a pipe.

The code is as follows:

$ sed -e 's/foo/bar/g' -e 's/chicken/cow/g' file1.xml > file2.xml

or

$ cat fixup.sed

s/foo/bar/g

s/chicken/cow/g

...

$ sed -f fixup.sed file1.xml > file2.xml

3.2.8 Operation of sed

Each file name on the command line is opened and read in turn. If there is no file, standard input is used.

Sed reads each file, one line at a time, and places the read lines in an area of memory (pattern space).

All actions on the edit are applied to the contents of the pattern space, and when all actions are complete, sed will change the pattern

The last content of the space is printed to standard output, and then back to the beginning to read another input line.

3.3 field handling

Use spaces (tabs) or special delimiters (such as colons).

A line starting with the #character indicates a comment, and software must be able to ignore such a line.

The best example of delimiting fields is/etc/passwd: one line represents a user, and each field is separated by a colon.

The file contains seven fields:

tolstoy:x:2076:10:Leo Tolstoy:/home/tolstoy:/bin/bash

1. User Name:2. Encrypted Password:3. User ID:4. User Group ID:5. Name:6. Root Directory:7. Logged in Shell.

3.3.2 Use cut to select fields

The code is as follows:

$ cut -d : -f 1,5 /etc/passwd

root:root

...

tolstoy:Leo Tolstoy

$ cut -d : -f 6 /etc/passwd

/root

...

/home/tolstoy

3.3.3 Using join fields

Combine multiple files with a common key (primary field).

$ cat sales

#Number of employees

joe 100

jane 200

herman 150

chris 300

$ cat quotas

#Salesman quota

joe 50

jane 75

herman 80

chris 95

The code is as follows:

#! /bin/sh

# merge-sales.sh

#Remove comments and sort data files

sed '/^#/d' quotas | sort > quotas.sorted

sed '/^#/d' sales | sort > sales.sorted

#Combine with the first key

join quotas.sorted sales.sorted

#Delete cache files

rm quotas.sorted sales.sorted

3.3.4 Using awk to rearrange fields

awk program basic architecture: pattern { action }

A pattern is usually an ERE enclosed by slashes, and an action is usually an explicit print statement.

Omitting pattern executes an action on each input record, omitting action is equivalent to { print }.

awk automatically divides each record into fields and stores the number of fields in each record in the built-in variable NF.

The default is white-space delimited, and you can also set the FS variable to a different value.$ Add a number to indicate the field value.

awk '{ print $1 }' Print 1st field

awk '{ print $2, $5 }' Print the 2nd and 5th fields

awk '{ print $1, $NF }' Print first and last fields

awk 'NF > 0 { print $0 }' Print nonblank lines

awk 'NF > 0' ditto

awk -F : '{ print $1, $5 }' /etc/passwd Sets the field separator character, the-F option automatically sets the FS variable.

root root

...

tolstoy Leo Tolstoy

Remember to separate print arguments with commas, otherwise awk concatenates all adjacent values.

awk -F: '{ print "User" $1 "is really" $5 }' /etc/passwd

Userrootis reallyroot

...

Usertolstoyis reallyLeo Tolstoy

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