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[Translated] 10 Lesser Known Commands for Linux – Part 3
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10 Lesser Known Commands for Linux – Part 3
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================================================================================
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We have come up with the third article of this series which includes few other lesser known Linux commands, worth knowing. May be you are already aware of these commands, no doubt you are an experienced Linux user and loves exploration.
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### 22. ^foo^bar Command ###
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Run the last command with modification, in a single instance. Suppose I need to run a command ‘**ls -l**‘ to long list the content of a directory say ‘**Desktop**’. Accidentally, you type ‘**lls -l**‘. So now you will have to retype the whole command or edit the previous command using navigation key. That is painful when the command is long.
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avi@localhost:~/Desktop$ lls -l
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bash: lls: command not found
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avi@localhost:~/Desktop$ ^lls^ls
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ls -l
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total 7489440
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drwxr-xr-x 2 avi avi 36864 Nov 13 2012 101MSDCF
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-rw-r--r-- 1 avi avi 206833 Nov 5 15:27 1.jpg
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-rw-r--r-- 1 avi avi 158951 Nov 5 15:27 2.jpg
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-rw-r--r-- 1 avi avi 90624 Nov 5 12:59 Untitled 1.doc
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**Note**: In the above replacement we used “**^typo(to be replaced)^original_command**”. This command may be very dangerous if you knowingly or unknowingly replaced the typo with system command or anything risky say **rm -rf**.
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### 23. > file.txt Command ###
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This command flush the contents of a file without the need of removing and creating the same file again. This command is very useful in scripting language when we need an output or log on the same file again and again.
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I have a file say ‘**test.txt**’ on my ‘**Desktop**‘ with a lot of text.
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avi@localhost:~/Desktop$ cat test.txt
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Linux
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GNU
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Debian
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Fedora
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kali
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ubuntu
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git
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Linus
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Torvalds
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avi@localhost:~/Desktop$ > test.txt
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avi@localhost:~/Desktop$ cat test.txt
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**Note**: Again, this command can be dangerous, don’t ever try to flush the contents of a system file or configuration file. If you do so, you will be in serious trouble.
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### 24. at Command ###
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The ‘**at**‘ command is similar to [cron command][1] and can be used for scheduling a task or command to run at specified time.
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avi@localhost:~/Desktop$ echo "ls -l > /dev/pts/0" | at 14:012
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OR
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avi@localhost:~/Desktop$ echo "ls -l > /dev/pts/0" | at 2:12 PM
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**Sample Output**
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-rw-r--r-- 1 avi avi 220492 Nov 1 13:49 Screenshot-1.png
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-rw-r--r-- 1 root root 358 Oct 17 10:11 sources.list
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-rw-r--r-- 1 avi avi 4695982080 Oct 10 20:29 squeeze.iso
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..
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..
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-rw-r--r-- 1 avi avi 90624 Nov 5 12:59 Untitled 1.doc
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-rw-r--r-- 1 avi avi 96206 Nov 5 12:56 Untitled 1.odt
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-rw-r--r-- 1 avi avi 9405 Nov 12 23:22 Untitled.png
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**Note**: echo “**ls -l**” : This string echo’s the command (here **ls -l**) on standard terminal. You can replace ‘**ls -l**‘ with any command of your need and choice.
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> : redirects the output
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The **/dev/pts/0** : This is the output device and/or file, where output is sought, here the output is at terminal.
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In my case, my **tty** is at **/dev/pts/0**, at that time. You can check your **tty** by running command **tty**.
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avi@localhost:~/Desktop$ tty
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/dev/pts/0
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**Note**: The ‘**at**‘ command execute the task as soon as the system clock matches the specified time.
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### 25. du -h –max-depth=1 Command ###
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The below command outputs the size of sub-folders within the current directory, in human readable format.
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avi@localhost:/home/avi/Desktop# du -h --max-depth=1
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38M ./test
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1.1G ./shivji
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42M ./drupal
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6.9G ./101MSDCF
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16G .
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**Note**: The above command can be very much useful in [checking system disk usage][2].
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### 26. expr Command ###
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The ‘**expr**‘ command is not that much lesser known command. This command is very much useful in carrying out simple mathematical calculation in terminal.
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avi@localhost:/home/avi/Desktop# expr 2 + 3
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5
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avi@localhost:/home/avi/Desktop# expr 6 – 3
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3
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avi@localhost:/home/avi/Desktop# expr 12 / 3
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4
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avi@localhost:/home/avi/Desktop# expr 2 \* 9
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18
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### 27. look Command ###
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Check for words from English dictionary in case of confusion, from the terminal itself. Viz., I am a bit confused if the spelling is carrier or carieer.
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avi@localhost:/home/avi/Documents# look car
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Cara
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Cara's
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…
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...
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carps
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carpus
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carpus's
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carrel
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carrel's
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carrels
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carriage
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carriage's
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carriages
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carriageway
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carriageway's
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carried
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carrier
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carrier's
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carriers
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carries
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…
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...
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caryatids
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The above command showed all the words from dictionary starting with string ‘car’. I got what I was searching for.
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### 28. yes Command ###
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Another command which is not used frequently on regular basis, normally but is very useful in scripting language and for system Administrators.
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This command continues to print a given string, till interrupt instruction is given by you.
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avi@localhost:~/Desktop$ yes "Tecmint is one of the best site dedicated to Linux, how to"
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Tecmint is one of the best site dedicated to Linux, how to
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Tecmint is one of the best site dedicated to Linux, how to
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Tecmint is one of the best site dedicated to Linux, how to
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Tecmint is one of the best site dedicated to Linux, how to
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…
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…
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...
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Tecmint is one of the best site dedicated to Linux, how to
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Tecmint is one of the best site dedicated to Linux, how to
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Tecmint is one of the best site dedicated to Linux, how to
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### 29. factor Command ###
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The factor command is actually a command of mathematical origin. This command outputs all the factors of a given number.
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avi@localhost:~/Desktop$ factor 22
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22: 2 11
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avi@localhost:~/Desktop$ factor 21
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21: 3 7
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avi@localhost:~/Desktop$ factor 11
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11: 11
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### 30. ping -i 60 -a IP_address ###
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All of us use ping command to check is server is live or not. And I usually ping google, to check if I am connected to internet or not.
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It is sometimes irritating, when you wait and keep watching your terminal to get reply of ping command or say, wait for server to get connected.
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How about an audible sound as soon as the server comes live.
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avi@localhost:~/Desktop$ ping -i 60 -a www.google.com
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PING www.google.com (74.125.200.103) 56(84) bytes of data.
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64 bytes from www.google.com (74.125.200.103): icmp_req=1 ttl=44 time=105 ms
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64 bytes from 74.125.200.103: icmp_req=2 ttl=44 time=281 ms
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Let me tell you one thing, before you report that the command didn’t return any audible sound. Make sure your system audio is not mute, sound theme must be enabled in ‘**sound preferences**‘ and make sure ‘**Enable window and window sound**‘ is checked.
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### 31. tac Command ###
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This command is very interesting which prints the content of a text file in **reverse order**, i.e., from last line to first line.
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I have a text file 35.txt in my Documents directory, under home folder. Checking it’s content using [cat command][3].
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avi@localhost:~/Documents$ cat 35.txt
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**Sample Output**
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> 1. Linux is built with certain powerful tools, which are unavailable in windows.
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> 2. One of such important tool is Shell Scripting. Windows however comes with such a tool but as usual it is much weak as compared to it's Linux Counterpart.
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> 3. Shell scripting/programming makes it possible to execute command(s), piped to get desired output in order to automate day-to-day usages.
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Now reverse the content of file using tac command.
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avi@localhost:~/Documents$ tac 35.txt
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**Sample Output**
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> 3. Shell scripting/programming makes it possible to execute command(s), piped to get desired output in order to automate day-to-day usages.
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> 2. One of such important tool is Shell Scripting. Windows however comes with such a tool but as usual it is much weak as compared to it's Linux Counterpart.
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> 1. Linux is built with certain powerful tools, which are unavailable in windows.
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That’s all for now. If you are aware of other lesser known Linux commands, you can put a comment, so that we can include those in our future articles.
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Don’t forget to provide us with your value-able comment. I’ll be soon coming with another interesting article, very soon. Till then stay tuned and connected to **Tecmint**.
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--------------------------------------------------------------------------------
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via: http://www.tecmint.com/10-lesser-known-commands-for-linux-part-3/
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译者：[译者ID](https://github.com/译者ID) 校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](http://linux.cn/) 荣誉推出
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[1]:http://www.tecmint.com/11-cron-scheduling-task-examples-in-linux/
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[2]:http://www.tecmint.com/check-linux-disk-usage-of-files-and-directories/
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[3]:http://www.tecmint.com/13-basic-cat-command-examples-in-linux/
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235
translated/10 Lesser Known Commands for Linux – Part 3.md
Normal file
235
translated/10 Lesser Known Commands for Linux – Part 3.md
Normal file
@ -0,0 +1,235 @@
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10个鲜为人知的Linux命令(3)
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================================================================================
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为了已经进入了10个鲜为人知Linux命令谢列的第三部分，这些都值得了解。或许你已经知道了这些命令，你无疑是一个有经验的Linux用户并喜欢探索。
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### 22. ^foo^bar 命令 ###
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在一个实例中运行修改后的最后一个命令。假设我需要运行一个命令‘**ls -l**‘来详细列出‘**Desktop**’目录下的内容。意外地，你打了‘**lls -l**‘。所以你需要重新打整个命令或者使用导航键编辑前面的命令。当你的命令很长时这个很痛苦。
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avi@localhost:~/Desktop$ lls -l
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bash: lls: command not found
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avi@localhost:~/Desktop$ ^lls^ls
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ls -l
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total 7489440
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drwxr-xr-x 2 avi avi 36864 Nov 13 2012 101MSDCF
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-rw-r--r-- 1 avi avi 206833 Nov 5 15:27 1.jpg
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-rw-r--r-- 1 avi avi 158951 Nov 5 15:27 2.jpg
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-rw-r--r-- 1 avi avi 90624 Nov 5 12:59 Untitled 1.doc
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**注意**:在上面的替换中我们使用“**^typo(被替换的)^original_command(原始命令)**”。这个命令可能会非常危险如果你有意或者无意地打错了系统命令或者任何像**rm -rf**那样的风险命令。
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### 23. > file.txt 命令 ###
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这个命令会刷新文件的内容而不需移除或者创建相同的文件。当我们反复需要一个输出或者在相同的文件上记录日志时，这个命令在脚本语言中非常有用。
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我有一个有很多文字的‘**test.txt**’文件在我的‘**Desktop**‘上。
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avi@localhost:~/Desktop$ cat test.txt
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Linux
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GNU
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Debian
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Fedora
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kali
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ubuntu
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git
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Linus
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Torvalds
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avi@localhost:~/Desktop$ > test.txt
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avi@localhost:~/Desktop$ cat test.txt
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**注意**:再说一次，这个命令可能很危险，永远不要尝试刷新系统文件或者篇日志文件的内容。如果你这么做了，你可能会遭遇严重的问题。
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### 24. at 命令 ###
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‘**at**‘命令与[cron 命令][1]相似也可用于安排一个任务或者在某个特定时刻执行命令。
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avi@localhost:~/Desktop$ echo "ls -l > /dev/pts/0" | at 14:012
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OR
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avi@localhost:~/Desktop$ echo "ls -l > /dev/pts/0" | at 2:12 PM
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**示例输出**
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-rw-r--r-- 1 avi avi 220492 Nov 1 13:49 Screenshot-1.png
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-rw-r--r-- 1 root root 358 Oct 17 10:11 sources.list
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-rw-r--r-- 1 avi avi 4695982080 Oct 10 20:29 squeeze.iso
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..
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..
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-rw-r--r-- 1 avi avi 90624 Nov 5 12:59 Untitled 1.doc
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-rw-r--r-- 1 avi avi 96206 Nov 5 12:56 Untitled 1.odt
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-rw-r--r-- 1 avi avi 9405 Nov 12 23:22 Untitled.png
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**注意**:echo “**ls -l**”: 这串echo命令(这里是 **ls -l**)输出在标准终端上。你可以用你需要或者选择的命令替代‘**ls -l**‘。
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> : 重定向输出
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**/dev/pts/0**: 这是输出设备与/或者文件，输出到被寻找的地方，这里输出在终端。
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就我而言，此时我的**tty**在**/dev/pts/0**。你可以用**tty**命令检查你的**tty**。
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avi@localhost:~/Desktop$ tty
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/dev/pts/0
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**注意**: ‘**at**‘会在系统时间匹配到特定时间时会尽快执行。
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### 25. du -h –max-depth=1 命令 ###
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下面的命令以人类可读的形式输出当前目录的子目录的大小。
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avi@localhost:/home/avi/Desktop# du -h --max-depth=1
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38M ./test
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1.1G ./shivji
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42M ./drupal
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6.9G ./101MSDCF
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16G .
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**注意**:上面的命令在[检查系统使用率][2]是非常有用。
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### 26. expr 命令 ###
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‘**expr**‘不是那么鲜为人知的命令。这个命令在终端中计算简单的算数时非常有用。
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avi@localhost:/home/avi/Desktop# expr 2 + 3
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5
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avi@localhost:/home/avi/Desktop# expr 6 – 3
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3
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avi@localhost:/home/avi/Desktop# expr 12 / 3
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4
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avi@localhost:/home/avi/Desktop# expr 2 \* 9
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18
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### 27. look 命令 ###
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在终端上从英文字典上查单词以防混淆。也就是说，我混淆了是该拼成carrier还是carieer。
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avi@localhost:/home/avi/Documents# look car
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Cara
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Cara's
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…
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...
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carps
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carpus
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carpus's
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carrel
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carrel's
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carrels
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carriage
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carriage's
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carriages
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carriageway
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carriageway's
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carried
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carrier
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carrier's
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carriers
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carries
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…
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...
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caryatids
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上面的命令会显示字典上所有以'car'开头的单词。我得到了我想找的。
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### 28. yes 命令 ###
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另外一个命令在通常基础上并不会经常使用，但是在脚本语言和系统管理时非常有用。
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这个命令会持续地输出给定的字符串，直到由你的中断命令打断。
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avi@localhost:~/Desktop$ yes "Tecmint is one of the best site dedicated to Linux, how to"
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Tecmint is one of the best site dedicated to Linux, how to
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Tecmint is one of the best site dedicated to Linux, how to
|
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Tecmint is one of the best site dedicated to Linux, how to
|
||||
Tecmint is one of the best site dedicated to Linux, how to
|
||||
…
|
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…
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...
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Tecmint is one of the best site dedicated to Linux, how to
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Tecmint is one of the best site dedicated to Linux, how to
|
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Tecmint is one of the best site dedicated to Linux, how to
|
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### 29. factor 命令 ###
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factor实际是一个始于数学的命令。这个命令会输出所有给定数字的因数。
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avi@localhost:~/Desktop$ factor 22
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22: 2 11
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avi@localhost:~/Desktop$ factor 21
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21: 3 7
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avi@localhost:~/Desktop$ factor 11
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11: 11
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### 30. ping -i 60 -a IP_address ###
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我们都用ping命令检测服务器是否连通。我通常ping google，来检测我是否连接到了因特网。
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当你等待或者持续盯着你的终端等待命令的回应或者等待服务器的连接时，有时是很气人的。
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一旦服务器连通就有一个声音如何？
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avi@localhost:~/Desktop$ ping -i 60 -a www.google.com
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PING www.google.com (74.125.200.103) 56(84) bytes of data.
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64 bytes from www.google.com (74.125.200.103): icmp_req=1 ttl=44 time=105 ms
|
||||
64 bytes from 74.125.200.103: icmp_req=2 ttl=44 time=281 ms
|
||||
|
||||
让我告诉你一件事情，当你报告命令不会返回声音时。请确保你的系统不是静音的，声音已经在‘**sound preferences(声音选项)**‘ 中启用并确保勾选了‘**Enable window and window sound**‘。
|
||||
|
||||
### 31. tac 命令 ###
|
||||
|
||||
这个命令很有趣，他会以倒序输出文本文件的内容。也就是从最后一行到第一行。
|
||||
|
||||
在home目录下，我的Documents目录下有一个35.txt文件。用[cat 命令][3]检查内容。
|
||||
|
||||
avi@localhost:~/Documents$ cat 35.txt
|
||||
|
||||
**示例输出**
|
||||
|
||||
> 1. Linux is built with certain powerful tools, which are unavailable in windows.
|
||||
> 2. One of such important tool is Shell Scripting. Windows however comes with such a tool but as usual it is much weak as compared to it's Linux Counterpart.
|
||||
> 3. Shell scripting/programming makes it possible to execute command(s), piped to get desired output in order to automate day-to-day usages.
|
||||
|
||||
现在用tac命令反转文件内容。
|
||||
|
||||
avi@localhost:~/Documents$ tac 35.txt
|
||||
|
||||
**示例输出**
|
||||
|
||||
> 3. Shell scripting/programming makes it possible to execute command(s), piped to get desired output in order to automate day-to-day usages.
|
||||
> 2. One of such important tool is Shell Scripting. Windows however comes with such a tool but as usual it is much weak as compared to it's Linux Counterpart.
|
||||
> 1. Linux is built with certain powerful tools, which are unavailable in windows.
|
||||
|
||||
现在完了。如果你还知道其他一些Linux鲜为人知的命令，你可以在下面评论，那么我们你可以在以后的文章中包含进来。
|
||||
|
||||
不要忘了给我们有价值的评论。我很快会发另外有趣的文章。别走开继续关注 **Tecmint**。
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: http://www.tecmint.com/10-lesser-known-commands-for-linux-part-3/
|
||||
|
||||
译者：[geekpi](https://github.com/geekpi) 校对：[校对者ID](https://github.com/校对者ID)
|
||||
|
||||
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](http://linux.cn/) 荣誉推出
|
||||
|
||||
[1]:http://www.tecmint.com/11-cron-scheduling-task-examples-in-linux/
|
||||
[2]:http://www.tecmint.com/check-linux-disk-usage-of-files-and-directories/
|
||||
[3]:http://www.tecmint.com/13-basic-cat-command-examples-in-linux/
|
||||
Loading…
Reference in New Issue
Block a user