linux:shell_commands:line [Eureka Moment]

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====== Bash line shortcuts ======
===== Clear line =====

  * <key>Ctrl+U</key> - clear all the current line from the end to the beginning only if the cursor is at the end of the line.

You can then recall the cleared line with <key>Ctrl+Y</key> if you need.
  * <key>Ctrl+K</key> - clear all the current line from the beginning to the end only if the cursor is at the beginning of the line.

You can then recall the cleared line with <key>Ctrl+Y</key> if you need.
  * <key>Ctrl+W</key> - clear the previous word in the current line. For example if you have typed a command like git diff /path/to/some/file and you want to delete just the last parameter to the command, Ctrl+W is very useful.

You can then recall the cleared data using <key>Ctrl+Y</key> if you need.
  * <key>Ctrl+E</key><key>Ctrl+U</key> - move the cursor to the end of the line and clear all the current line from the end to the beginning.

You can then recall the cleared line with <key>Ctrl+Y</key> if you need.
  * <key>Ctrl+A</key><key>Ctrl+K</key> - move the cursor at the beginning of the line and clear all the current line from the beginning to the end.

You can then recall the cleared line with <key>Ctrl+Y</key> if you need.
  * <key>Ctrl+C</key> - cancel the current command line, which implies clear all the current line no matter where the cursor is.

Disadvantage: you can't recall the cleared line anymore.
  * <key>Alt+Shift+#</key> - comment the current line, keep it in the history and bring up your prompt on a new line.

===== History =====
Browse history with <key>Arrow Up</key> and <key>Arrow Down</key>

Browse through history with <key>Ctrl+R</key>, and by starting to type the command. If multiple commands with the same search pattern exist in history, press <key>Ctrl+R</key> again to loop through them.

<key>Ctrl+O</key> will run the selected command, and leave it in prompt

Typing the command **history** will display all history.

Also, you can grep the output like this: **history | grep apt**

Re-run a specific command from history referenced by command number: **!#**. **!70** will rerun the command on position 70 in history file

Re-run the previous command **!!**. This is helpful when you forget to sudo, so you can use **sudo !!** to sudo the previous command, or you can use **!! | grep text** to grep the output of the previous command.

Run a recent command by referencing to part of it: **!text**. If you recently user the command **ping 8.8.8.8**, you can re-run it by typing **!pi**

Adding **:p** to the above outputs will print the command into terminal. **!70:p**, **!!:p**, **!pi:p**

Reuse the last argument from previous command **!$**. If you user **ping 8.8.8.8**, you can then traceroute it by typing **traceroute !$**. Note that this only uses the last argument, so after **ping 8.8.8.8 -c 4** using it like **traceroute !$** will result with **traceroute 4**.

Reuse the first argument from previous command **!^**, so after **ping 8.8.8.8 -c 4**, using **traceroute !^** will result with **traceroute 8.8.8.8**.

Reuse all arguments from previous command with **!***, so after **ping 8.8.8.8 -c 4**, using **ping !*** will result with **ping 8.8.8.8 -c 4**.

You can combine this with the command history: **command !abc:#** or **command !abc:***

Correct the previous command with **^abc^xyz**
<code bash>
su@www:~$ ping gogle.com
^C
su@www:~$ ^gog^goog
ping google.com
PING google.com (216.58.214.238) 56(84) bytes of data.
64 bytes from bud02s24-in-f238.1e100.net (216.58.214.238): icmp_seq=1 ttl=115 time=10.9 ms
64 bytes from bud02s24-in-f238.1e100.net (216.58.214.238): icmp_seq=2 ttl=115 time=11.0 ms
64 bytes from bud02s24-in-f238.1e100.net (216.58.214.238): icmp_seq=3 ttl=115 time=11.1 ms
^C
--- google.com ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2003ms
rtt min/avg/max/mdev = 10.917/11.020/11.105/0.077 ms
su@www:~$
</code>
**history -c** will clear the history.

Configuring the **HISTCONTROL** variable allows to not store commands beginning with space, or duplicate commands - or both.
<code bash>
HISTCONTROL=ignorespace
HISTCONTROL=ignoredups
HISTCONTROL=ignoreboth
</code>