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Eight Shell commands to make you a Linux command line master in no time
Eight Shell commands to make you a Linux command line master in no time
Jun 17, 2023 am 09:38 AM
Having a solid programming foundation is obviously an essential quality for a good software engineer. It is very important to master at least one programming language, whether it is an interpreted language such as Python, or a compiled language such as C. However, this is only one aspect of becoming a truly well-rounded engineer. Those basics are of no use if you're lost in the shell environment.
The flexible application of Bash commands allows you to enter areas that traditional programming languages ??cannot cover. Sometimes, you don't actually need to use a more powerful programming language. Using the Shell, you can accomplish the tasks you need faster and more easily, without the need for additional dependencies.
In this article, we will explore some very useful Bash commands. These commands can help you avoid writing more code than you actually need. Next time you encounter a problem, try these commands.
1. Loop Command
linuxmi@linuxmi:~/www.linuxmi.com$ while true; do echo "hello $(date)"; sleep 1; done
You don’t have to jump into a huge programming language just to loop something. Getting output at regular intervals or iterating over basic data is easy to do in Bash.
This line of code demonstrates how to build a simple infinite while loop in the Shell. You just splice everything together with a semicolon and you're done. You are free to change the command executed and adjust the sleep timer accordingly.
When you run this command, you should see the date change every second on your terminal.
2. Output redirection
linuxmi@linuxmi:~/www.linuxmi.com$ echo "hello linux迷 www.linuxmi.com" | tee linuxmi.rs | less
The tee command can achieve functions that require multiple lines of code in other languages. Using this handy little tool, you can send certain input to a file or other command, which can then be passed to another command. It's actually like installing a "T" valve in your water pipe. You can direct a portion of the output out and it will continue to flow down the pipe.
The above example sends the "hello linux fan www.linuxmi.com" text obtained from the echo command to the linuxmi.rs file, and then proceeds to send it to less. One way to rewrite it is: you will get a file with the output content, and you can view it on the screen using the less command.
3. Compress files
linuxmi@linuxmi:~/www.linuxmi.com$ tar -czvf linuxmi.tar.gz linuxmi.sh
Moving files and directories on the command line is an important skill. If you're working on something and need to move it between hosts, or just want to compress a file for offline storage, the tar command is your friend.
Using the above commands and options, you can compress a directory into a new tar.gz compressed package. Now you can bring your files quickly.
4. Counting
linuxmi@linuxmi:~/www.linuxmi.com$ echo -e "linuxmi\n linuxmi.com\n www.linuxmi.com\n www.93139.com" > linuxmi.txt | wc -l
Want to know how many lines there are in the file? Very simple. Use wc utility. "Word count" is what it actually means, but it can also be used to count many other things, such as the number of lines.
The above snippet outputs four lines of text to a file and then uses wc to count the number of lines. This tool is useful if you need to manipulate a certain number of lines or confirm whether a process has written new lines to a file.
5. Generate numbers
linuxmi@linuxmi:~/www.linuxmi.com$ seq 95 100
So simple, but very helpful. Generating numbers in Bash is very easy, just use the seq utility. This neat little command outputs a sequence of numbers that you can use in loops, text files, or anywhere else you need a list of numbers.
You can also change the delimiter if needed:
seq -s " " 1 10
or
echo {0..10}
This will separate all numbers with spaces instead of the default newline. You can also use the echo command and the .. operator to obtain the same type of results.
6. Manage your SSH keys
linuxmi@linuxmi:~/www.linuxmi.com$ eval $(ssh-agent) && ssh-add && ssh-add -l
A basic understanding of SSH keys and how to manage them is absolutely necessary. You may find that understanding the ssh-add and ssh-agent utilities can be more beneficial than you think.
The above command performs several important operations:
- eval命令將為你執(zhí)行ssh-agent，并確保它在后臺運行。
- ssh-add命令將添加你的默認(rèn)SSH密鑰。如果你為默認(rèn)密鑰設(shè)置了密碼，它將提示你輸入密碼。
- 最后，ssh-add -l命令顯示當(dāng)前在你的代理中添加的所有密鑰。
這個簡單的一行命令確保你的代理工作正常，并包含了正確的密鑰。當(dāng)你需要連接到某個服務(wù)或獲取一些代碼時，下一步就可以直接開始了。
7、查找過去的命令
linuxmi@linuxmi:~/www.linuxmi.com$ history | grep "top"
或者按下CTRL + R，然后輸入top
還記得很久以前運行的那個命令嗎？我也不記得了。在歷史記錄中搜索它吧。
如果你像我一樣記憶力不太好，那么history命令非常有用。它會顯示當(dāng)前終端會話中所有已運行的命令列表。反向交互式搜索或grep工具的真正威力在于能夠找到之前執(zhí)行的命令。
如果你只是想查看命令歷史記錄而不是執(zhí)行它，你可以使用grep搜索。要統(tǒng)一搜索和執(zhí)行操作，你可以使用CTRL + R的反向交互式搜索歷史記錄組合鍵。一旦按下快捷鍵，一個交互提示符就會出現(xiàn)，當(dāng)你開始輸入命令時，控制臺會顯示相應(yīng)的匹配命令。
8、將多個命令作為一個整體傳遞
linuxmi@linuxmi:~/www.linuxmi.com$ history | grep "top"
有時Bash會變得有點奇怪。變量插值可能出錯，嵌套引號可能會混亂且難以跟蹤。情況將變得更加復(fù)雜，尤其是當(dāng)你需要在不同的二進制文件或服務(wù)中傳遞命令字符串時。在這種情況下，你可以使用bash命令將一組命令作為單個實體進行評估。
這個指令將接收純文本字符串，然后按照常規(guī)的Bash語法來進行解析。對于外部shell來說，你只是運行一個命令并傳遞一個參數(shù)，但實際上你是在指示Bash解析多個命令的字符串并執(zhí)行它們。
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