Implementation of Linux command line wildcards and escape characters

If we want to perform batch operations on a type of files, such as batch viewing of hard disk file attributes, the normal command would be:

[root@linuxprobe ~]# ls /dev/sda
[root@linuxprobe ~]# ls /dev/sda1
[root@linuxprobe ~]# ls /dev/sda2
[root@linuxprobe ~]# ls /dev/sda3

But sometimes I really don't know the partition

Wildcards

An asterisk (*) matches zero or more characters.

huanyu@ubuntu:~$ ls -l /dev/sda* 

The question mark (?) matches a single character.

huanyu@ubuntu:~$ ls -l /dev/sda? 

The numbers [0-9] in the brackets match a single digit between 0 and 9, while the letters [abc] in the brackets match any one of the three characters a, b, and c.

huanyu@ubuntu:~$ ls -l /dev/sda[0-9]
huanyu@ubuntu:~$ ls -l /dev/sda[135] 

Example:

View all device files starting with sda:

[root@linuxprobe ~]# ls /dev/sda*
/dev/sda /dev/sda1 /dev/sda2

Check the device file with a character after sda:

[root@linuxprobe ~]# ls /dev/sda?
/dev/sda1 /dev/sda2

Check the device file containing 0-9 numbers after sda:

[root@linuxprobe ~]# ls /dev/sda[0-9]
/dev/sda1 /dev/sda2

Check the device file with 1, 3 or 5 after sda:

[root@linuxprobe ~]# ls /dev/sda[135]
/dev/sda1

Escape Character

Backslash (\): turns a variable following the backslash into a simple string

huanyu@ubuntu:~$ echo "Price is \$$PRICE" 

Backquotes (``): execute the command and return the result

huanyu@ubuntu:~$ echo `uname -a` 

Example

Define a variable named PRICE with a value of 5:

[root@linuxprobe ~]# PRICE=5

To output "price is 5":

[root@linuxprobe ~]# echo "Price is $PRICE"
Price is 5

I want to output "The price is $5", but because the dollar sign conflicts with the $ sign representing the variable value, an error is reported:

[root@linuxprobe ~]# echo "Price is $$PRICE"
Price is 3767PRICE

Add a backslash to escape the first $ sign:

[root@linuxprobe ~]# echo "Price is \$$PRICE"
Price is $5

Using single quotes, the variable will no longer be evaluated:

[root@linuxprobe ~]# echo 'Price is \$$PRICE'
Price is \$$PRICE

After executing uname -a, you can view the version and architecture information of the local kernel (the commands in backquotes will be executed):

[root@linuxprobe ~]# echo `uname -a`
Linux linuxprobe.com 3.10.0-123.el7.x86_64 #1 SMP Mon May 5 11:16:57 EDT 2014 x86_64 x86_64 x86_64 GNU/Linux

The above is the full content of this article. I hope it will be helpful for everyone’s study. I also hope that everyone will support 123WORDPRESS.COM.