Fc (short for Fix Commands) is a shell built-in command for listing, editing, and executing recently entered commands in an interactive shell. You can use your favorite editor to edit recent commands and execute them again without having to retype them all. In addition to the long and complicated commands that can be avoided, it is also useful for correcting misspellings. Because it is a shell built-in command, most shells include it, such as Bash, Zsh, Ksh, and so on. In this short article, we come to learn to use the fc command in Linux.
Fc command tutorials and examples
List recently executed commands
Execute the fc -l command with no arguments, it will list the last 16 commands.
$fc -l
507fish
508fc -l
509sudo netctl restart wlp9s0sktab
510ls -l
511pwd
512uname -r
513uname -a
514touch ostechnix.txt
515vi ostechnix.txt
516echo"Welcome to OSTechNix"
517sudo apcman -Syu
518sudo pacman -Syu
519more ostechnix.txt
520wc -lostechnix.txt
521cat ostechnix.txt
522clear
The -r option is used to reverse the output.
$fc -lr
The -n option is used to hide the line number.
$fc -ln
Nano ~/.profile
Source ~/.profile
Source ~/.profile
Fc -ln
Fc -l
Sudo netctl restart wlp9s0sktab
Ls -l
Pwd
Uname -r
Uname -a
Echo"Welcome to OSTechNix"
Sudo apcman -Syu
Cat ostechnix.txt
Wc -lostechnix.txt
More ostechnix.txt
Clear
This line number is no longer displayed.
If you want to start with a command, just add the line number after the -l option. For example, to display line number 520 to the nearest command, you could do this:
$fc -l520
520ls -l
521pwd
522uname -r
523uname -a
524echo"Welcome to OSTechNix"
525sudo apcman -Syu
526cat ostechnix.txt
527wc -lostechnix.txt
528more ostechnix.txt
529clear
530fc ​​-ln
531fc -l
To list a range of commands, use the first and last line numbers as parameters of fc -l, such as 520 to 525:
$fc -l520525
520ls -l
521pwd
522uname -r
523uname -a
524echo"Welcome to OSTechNix"
525sudo apcman -Syu
In addition to using line numbers, we can also use characters. For example, to list all the commands between the most recent pwd to the most recent command, just use the start letter as follows:
$fc -lp
521pwd
522uname -r
523uname -a
524echo"Welcome to OSTechNix"
525sudo apcman -Syu
526cat ostechnix.txt
527wc -lostechnix.txt
528more ostechnix.txt
529clear
530fc ​​-ln
531fc -l
532fc -l520
533fc -l520525
534fc -l520
535fc -l522
536fc -ll
To list all commands between pwd and more, you can use the starting letters like this:
$fc -lpm
Or, use the first letter of the start command and the line number of the end command:
$fc -lp528
Or use the line number:
$fc -l521528
All three commands show the same result.
Edit and execute the previous command
We often type wrong commands. At this point, you can use the default editor to correct spelling mistakes and execute them without having to repeat the command again.
Edit and execute the previous command:
$fc
This will load the previous command in the default editor.
As you can see, my previous command was fc -l. You can modify it as you like. It will be executed automatically when you save and exit the editor. This is useful when the command or parameter is long and complicated. It should be noted that it may also be devastating. For example, if your last command is dangerous rm -fr
Change the default editor
Another useful option is -e , which can be used to select a different editor for the fc command. For example, if we want to use nano to edit the previous command:
$fc -enano
This command will open the nano editor (instead of the default editor) to edit the previous command.
If you find it too cumbersome to use the -e option, you can modify your default editor by setting the environment variable FCEDIT to the name of the editor you want fc to use.
For example, to set nano as the default editor, edit your ~/.profile or other initialization file: (LCTT: if ~/.profile does not exist, create it yourself; if you are using bash, edit ~/.bash_profile )
$vi ~/.profile
Add the following line:
FCEDIT=nano
# LCTT: If you use fc in a subshell, it is best to export FCEDIT here.
You can also use the full path of the editor:
FCEDIT=/usr/local/bin/emacs
Enter: wq Save and exit. To make changes effective immediately, run the following command:
$source ~/.profile
Now enter fc to edit the previous command using the nano editor.
Do not edit and execute the previous command directly
We now know that the fc command will load the previous command into the editor without any parameters. But sometimes you may not want to edit, just want to execute the previous command again. This is very simple, with a hyphen (-) at the end:
$echo"Welcome to OSTechNix"
Welcome toOSTechNix
$fc -e -
Echo"Welcome to OSTechNix"
Welcome toOSTechNix
As you can see, fc has the -e option, but it doesn't edit the previous command (example echo "Welcome to OSTechNix").
Note that some options are only valid for the specified shell. For example, the following options can be used in zsh but not in Bash or Ksh.
Display command execution time
To know when the command was executed, use the -d option:
Fc -ld
118:41exit
218:41clear
318:42fc -l
418:42sudo netctl restart wlp9s0sktab
518:42ls -l
618:42pwd
718:42uname -r
818:43uname -a
918:43cat ostechnix.txt
1018:43echo"Welcome to OSTechNix"
1118:43more ostechnix.txt
1218:43wc -lostechnix.txt
1318: 43cat ostechnix.txt
1418:43clear
1518:43fc -l
This way you can see the specific execution time of the most recent command.
With the -f option, a complete time stamp can be displayed for each command.
Fc -lf
14/5/201818:41exit
24/5/201818:41clear
34/5/201818:42fc -l
44/5/201818:42sudo netctl restart wlp9s0sktab
54/5/201818:42ls -l
64/5/201818:42pwd
74/5/201818:42uname -r
84/5/201818:43uname -a
94/5/201818:43cat ostechnix.txt
104/5/201818:43echo"Welcome to OSTechNix"
114/5/201818:43more ostechnix.txt
124/5/201818:43wc -lostechnix.txt
134/5/201818:43cat ostechnix.txt
144/5/201818:43clear
154/5/201818:43fc -l
164/5/201818:43fc -ld
Of course, European villagers can also use the -E option to display the European time format.
Fc -lE
25.4.201818:41clear
35.4.201818:42fc -l
45.4.201818:42sudo netctl restart wlp9s0sktab
55.4.201818:42ls -l
65.4.201818:42pwd
75.4.201818:42uname -r
85.4.201818:43uname -a
95.4.201818: 43cat ostechnix.txt
105.4.201818:43echo"Welcome to OSTechNix"
115.4.201818:43more ostechnix.txt
125.4.201818:43wc -lostechnix.txt
135.4.201818:43cat ostechnix.txt
145.4.201818:43clear
155.4.201818:43fc -l
165.4.201818:43fc -ld
175.4.201818:49fc -lf
Fc usage summary
When no parameters are present, fc loads the previous command into the default editor.
When you take a number as a parameter, fc loads the numerically specified command into the default editor.
When you take a character as a parameter, fc loads the most recent command that starts with the specified character into the default editor.
When there are two parameters, they specify the beginning and end of the range of commands that need to be listed.
For more details, please refer to the man manual.
$man fc
Well, today is this. Hope this article will help you.
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