Standard Linux Commands - blame None

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ae6cb8	Arpan S.	2024-03-29 11:28:56	1	# Standard Linux Commands
460022	Arpan S.	2024-03-29 11:41:37	2
			3	This page contains some standard linux commands that are available for use across all linux systems but are easy to forget that they exist or using them can get confusing sometimes.
			4
ca2477	Arpan S.	2024-03-29 20:45:25	5	#### `wc` Command
845283	Arpan S.	2024-03-29 21:30:48	6	This command is used to count things in linux and supports piping. It can be used for multiple purposes as shown below.
ca2477	Arpan S.	2024-03-29 20:45:25	7
			8	Syntax:
			9	```
			10	wc OPTION... [FILE]...
			11	```
342d25	Arpan S.	2024-03-29 21:28:17	12	###### Options
ca2477	Arpan S.	2024-03-29 20:45:25	13
342d25	Arpan S.	2024-03-29 21:28:17	14	- `-l` / `--lines` - Print number of lines.
			15	- `-w` / `--words` - Print number of words.
			16	- `-m` / `--chars` - Print the number of characters.
			17	- `-c` / `--bytes` - Print the number of bytes.
			18	- `-L` / `--max-line-length` - Print the length of the longest line.
			19
			20	Default Output:
			21
			22	```
			23	# wc fileA
			24	20 30 60 fileA
			25	```
			26	Here, _20_ is the number of lines, _30_ is the number of words & _60_ is the number of characters in the file.
			27
			28	Generic uses:
			29
			30	Standard usage (Pipe Back)
			31	```
			32	wc < fileA
			33	```
			34
			35	Multiple Files
			36	```
			37	# wc fileA fileB
			38	```
			39	_Output:_
			40	```
			41	20 40 60 fileA
			42	60 80 100 fileB
			43	80 120 160 total
			44	#
			45	```
			46
			47	Number of words (Piped Output)
			48	```
			49	cat /etc/shadow \| wc -w
			50	```
			51
			52	Number of lines (Piped Output)
			53	```
			54	cat /etc/shadow \| wc -l
			55	```
			56
			57	###### How to count number of lines in a file using `wc`
			58	```
			59	wc -l /path/to/file
			60	```
			61
			62	###### How to count number of words in a file using `wc`
			63	```
			64	wc -w /path/to/file
			65	```
			66
			67	###### How to count number of lines output by a command using `wc`
			68	```
			69	example_command \| wc -l
			70	```
			71
			72	###### How to count number of files in current directory using `wc`
			73	```
			74	find . -type f \| wc -l
			75	```
			76
ca2477	Arpan S.	2024-03-29 20:45:25	77
b7eea6	Arpan S.	2024-03-29 12:51:07	78	#### `ln` Command - How to create symbolic links / sys links in Linux.
			79
			80	##### General Explaination and use-case
			81
			82	There are two types of system links in linux:
2932d9	Arpan S.	2024-03-29 13:00:48	83	1. Hard Links: Its is like having an alias name to an existing file. It links _(better term: syncs)_ two or more file names with the same [inode](https://en.wikipedia.org/wiki/Inode). You can only create hardlinks for files & folders on the same filesystem or partition. One file can have multiple hardlinks.
b7eea6	Arpan S.	2024-03-29 12:51:07	84	2. Soft Links: A soft link can be related to a shortcut in windows, it allows a file to be accessed from one directory to other without having to keep 2 copies of it. Soft Links can be created across different filesystems and partitions.
			85
			86	##### How to use ln command
			87
			88	By default `ln` command creates Hard Links, To make Soft Links, We can use the `-s` _(`--symbolic`)_ flag
			89
2932d9	Arpan S.	2024-03-29 13:00:48	90	Syntax:
b7eea6	Arpan S.	2024-03-29 12:51:07	91	```python
			92	ln -s [OPTIONS] SOURCE_FILE DESTINATION_LINK
			93	```
			94	`DESTINATION_LINK` is optional, If that is not specified then it will create a system link in the current working directory with the same name.
			95
			96	::: success
			97	The `ln` command provides no output if ran successfully.
			98	:::
			99
			100	>\| # Examples
			101	>\| SysLink a Normal file
			102	>\| ```
			103	>\| ln -s file1 file2
			104	>\| ```
			105	>\| SysLink a Normal file in different directories
			106	>\| ```
			107	>\| ln -s /root/file1 /var/www/html/file1
			108	>\| ```
			109	>\| SysLink a Normal Directory to another
			110	>\|
			111	>\| ```ln -s /root/downloads /downloads```
			112
			113	###### How to see if a file is a System Link:
			114	To see if a file is already a system link/sysLink/symbolic link, We can use the `ls` command with the `-l` flag. Syntax:
			115	```
			116	# ls -l syslinked_file
			117	lrwxrwxrwx 1 root root 9 Nov 22 2004 /root/og_file -> syslinked_file
			118	#
			119	```
			120
			121	###### How to overwrite a System Link:
			122	To overwrite an existing sysLink when the `DESTINATION_FILE` already exists as a sysLink, we can use the -f flag. Syntax Below:
			123	```
			124	ln -sf new-file.conf existing-syslink.conf
			125	```
			126
			127	###### How to remove/delete a System Link:
845283	Arpan S.	2024-03-29 21:30:48	128	To delete/remove a sysLink we can use the `rm` or `unlink` command. Please note that both commands work exactly the same._[Refrence](https://linuxize.com/post/how-to-remove-symbolic-links-in-linux/)_
b7eea6	Arpan S.	2024-03-29 12:51:07	129
			130	::: danger
			131	Removing or Moving away the Source file will cause the sysLink to break and it won't work anymore. its is best advised to remove any broken sysLinks.
			132	:::
			133
			134	Syntax:
			135
			136	`unlink` Command
			137	```
			138	unlink symlink_to_remove
			139	```
			140	`rm` Command
			141	```
			142	rm symlink_to_remove
			143	```