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6 Linux metacharacters I love to use on the command line
Using metacharacters on the Linux command line is a great way to enhance
productivity.
Early in my Linux journey, I learned how to use the command line. It's what sets Linux apart. I could lose the graphical user interface (GUI), but it was unnecessary to rebuild the machine completely. Many Linux computers run headless, and you can accomplish all the administrative tasks on the command line. It uses many basic commands that all are familiar with—like ls, ls-l, ls-l, cd, pwd, top, and many more.
Shell metacharacters on Linux
You can extend each of those commands through the use of metacharacters. I didn't know what you called them, but metacharacters have made my life easier.
Pipe |
Say that I want to know all the instances of Firefox running on my system. I can use the ps command with an -ef to list all instances of the programs running on my system. Now I'd like to see just those instances where Firefox is involved. I use one of my favorite metacharacters, the pipe | the result to grep, which searches for patterns.
`$ ps -ef | grep firefox `
Output redirection >
Another favorite metacharacter is the output redirection >. I use it to print the results of all the instances that Intel mentioned as a result of a dmesg command. You may find this helpful in hardware troubleshooting.
$ dmesg | grep amd > amd.txt
$ cat amd.txt
[ 0.897] amd_uncore: 4 amd_df counters detected
[ 0.897] amd_uncore: 6 amd_l3 counters detected
[ 0.898] perf/amd_iommu: Detected AMD IOMMU #0 (2 banks, 4 counters/bank).
Asterisk *
The asterisk * or wildcard is a favorite when looking for files with the same extension—like .jpg or .png. I first change into the Picture directory on my system and use a command like the following:
$ ls *.png
BlountScreenPicture.png
DisplaySettings.png
EbookStats.png
StrategicPlanMenu.png
Screenshot from 01-24 19-35-05.png
Tilde ~
The tilde ~ is a quick way to get back to your home directory on a Linux system by entering the following command:
$ cd ~
$ pwd
/home/don
Dollar symbol $
The $ symbol as a metacharacter has different meanings. When used to match patterns, it means any string that ends with a given string. For example, when using both metacharacters | and $:
$ ls | grep png$
BlountScreenPicture.png
DisplaySettings.png
EbookStats.png
StrategicPlanMenu.png
Screenshot from 01-24 19-35-05.png
Carat ^
The ^ symbol restricts results to items that start with a given string. For example, when using both metacharacters | and ^:
$ ls | grep ^Screen
Screenshot from 01-24 19-35-05.png
Many of these metacharacters are a gateway to regular expressions, so there's a lot more to explore. What are your favorite Linux metacharacters, and how are they saving your work?
via: https://opensource.com/article/22/2/metacharacters-linux
作者：Don Watkins 选题：lujun9972 译者：译者ID 校对：校对者ID