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--- sysadmin:linux:basic_commands [2025/12/16 02:39] – mlivolsi
+++ sysadmin:linux:basic_commands [2025/12/16 03:09] (current) – mlivolsi
@@ Line 6: / Line 6: @@
 |more filename | shows the first part of a file, just as much as will fit on one screen. Just hit the space bar to see more or q to quit. You can use /pattern to 	search for a pattern. |
-|head 	filename 	| 	show me the first lines of a file |
+|head 	filename 	| show me the first lines of a file |
-|tail 	filename 	| 	 show me the last lines of a file |
+|tail 	filename 	| show me the last lines of a file |
-|vi 	filename 	| 	Another editor (preferred)	|
+|vi 	filename 	| Another editor (preferred)	|
-|mv filename1 	filename2 | 	moves a file (i.e. gives it a different name, or moves it into a different directory (see below) (dos equivalent of rename)
+|mv filename1 	filename2 | moves a file (i.e. gives it a different name, or moves it into a different directory (see below) (dos equivalent of rename) |
-|cp filename1 	filename2 | 	copies a file (dos equivalent of copy)
+|cp filename1 filename2 | copies a file (dos equivalent of copy) |
-|rm filename |	removes a file. It is wise to use the option rm -i, which will ask you for confirmation before actually deleting anything. You can make 	this your default by making an alias in 	your .cshrc file. (dos equivalent of erase)
+|rm filename | removes a file. It is wise to use the option rm -i, which will ask you for confirmation before actually deleting anything. You can make this your default by making an alias in your .cshrc file. (dos equivalent of erase) |
-|diff filename1 filename2 | 	compares files, and shows where they differ |
+|diff filename1 filename2 | compares files, and shows where they differ |
 |wc filename    	  | tells you how many lines, words, and characters there are in a file |
-|chmod options 	filename |lets you change the read, write, and execute permissions on your 	files. The default is that only you can look at them and change 	them, but you may sometimes want to change these permissions. For 	example, chmod 	o+r filename will 	make the file readable for everyone, and chmod 	o-r filename will 	make it unreadable for others again. Note that for someone to be 	able to actually look at the file the directories it is in need to 	be at least executable. See help 	protection for 	more details.|
+|chmod options 	filename |lets you change the read, write, and execute permissions on your files. The default is that only you can look at them and change them, but you may sometimes want to change these permissions. For example, chmod o+r filename will make the file readable for everyone, and chmod o-r filename will 	make it unreadable for others again. Note that for someone to be able to actually look at the file the directories it is in need to be at least executable. See help protection for more details.|
 |tar 	–cvf filename.tar | Make a non-compressed aggregate of files|
 |tar 	–xvf filename.tar | Extract files out (files are known as ‘tarballs’)|
-File 	Compression
+**File Compression**
-gzip filename --- 		compresses files, so that they take up much less space. Usually 		text files compress to about half their original size, but it 		depends very much on the size of the file and the nature of the 		contents. There are other tools for this purpose, too 		(e.g. compress), 		but gzip usually gives the highest compression rate. Gzip produces 		files with the ending '.gz' appended to the original filename.
+| gzip filename | compresses files, so that they take up much less space. Usually text files compress to about half their original size, but it 		depends very much on the size of the file and the nature of the contents. There are other tools for this purpose, too (e.g. compress), but gzip usually gives the highest compression rate. Gzip produces files with the ending '.gz' appended to the original filename.|
-gunzip filename --- 		uncompresses files compressed by gzip.
+| gunzip filename | uncompresses files compressed by gzip.|
+| gzcat filename | lets you look at a gzipped file without actually having to gunzip it (same as gunzip  -c). You can even print it directly, using gzcat filename | lpr
-gzcat filename --- 		lets you look at a gzipped file without actually having to gunzip 		it (same as gunzip 		-c). 		You can even print it directly, using gzcat filename | 		lpr
-Directories
+**Directories**
- mkdir dirname --- 	make a new directory
-cd dirname --- 	change directory. You basically 'go' to another directory, and you 	will see the files in that directory when you do 'ls'. You always 	start out in your 'home directory', and you can get back there by 	typing 'cd' without arguments. 'cd ..' will get you one level up 	from your current position. You don't have to walk along step by 	step - you can make big leaps or avoid walking around by 	specifying pathnames.
+| mkdir dirname | make a new directory |
-pwd --- 	tells you where you currently are.
+| cd dirname | change directory. You basically 'go' to another directory, and you will see the files in that directory when you do 'ls'. You always start out in your 'home directory', and you can get back there by typing 'cd' without arguments. 'cd ..' will get you one level up from your current position. You don't have to walk along step by step - you can make big leaps or avoid walking around by specifying pathnames.|
-Finding things
+| pwd | tells you where you currently are.|
+**Finding things**
-find 	--- 	find files anywhere on the system. This can be extremely useful if 	you've forgotten in which directory you put a file, but do remember 	the name. (ie. find 	. –name foo.bar –print 	 )
+|find |find files anywhere on the system. This can be extremely useful if you've forgotten in which directory you put a file, but do remember the name. (ie. find . –name foo.bar –print )|
+|grep string 	filename(s) | looks for the string in the files. This can be useful a lot of purposes, e.g. finding the right file among many, figuring out which is the right version of something, and even doing serious corpus 	work. grep comes in several varieties (grep, egrep, and fgrep) and has a lot of very flexible options. Check out the man pages if this sounds good to you.|
-grep string 	filename(s) --- 	looks for the string in the files. This can be useful a lot of 	purposes, e.g. finding the right file among many, figuring out which 	is the right version of something, and even doing serious corpus 	work. grep comes in several varieties (grep, egrep, 	and fgrep) 	and has a lot of very flexible options. Check out the man pages if 	this sounds good to you.
-About other people
-w --- 	tells you who's logged in, and what they're doing. Especially 	useful: the 'idle' part. This allows you to see whether they're 	actually sitting there typing away at their keyboards right at the 	moment.
-who --- 	tells you who's logged on, and where they're coming from. Useful if 	you're looking for someone who's actually physically in the same 	building as you, or in some other particular location.
+**About other people**
-finger username --- 	gives you lots of information about that user, e.g. when they last 	read their mail and whether they're logged in. Often people put 	other practical information, such as phone numbers and addresses, in 	a file called .plan. 	This information is also displayed by 'finger'
-last 	-1 username --- 	tells you when the user last logged on and off and from where. 	Without any options, last will 	give you a list of everyone's logins.
+|w |tells you who's logged in, and what they're doing. Especially useful: the 'idle' part. This allows you to see whether they're actually sitting there typing away at their keyboards right at the  moment.|
-About your (electronic) self
+|who |tells you who's logged on, and where they're coming from. Useful if you're looking for someone who's actually physically in the same building as you, or in some other particular location.|
-whoami --- 	returns your username. Sounds useless, but isn't. You may need to 	find out who it is who forgot to log out somewhere, and make sure 	*you* have logged out.
+|finger username | gives you lots of information about that user, e.g. when they last read their mail and whether they're logged in. Often people put other practical information, such as phone numbers and addresses, in a file called .plan. This information is also displayed by 'finger'|
-finger
+|last -1 username | tells you when the user last logged on and off and from where. Without any options, last will give you a list of everyone's logins.|
- of course you can finger yourself, too. That can be useful 	e.g. as a quick check whether you got new mail. Try to create a 	useful .plan file soon. Look at other people's .plan files for 	ideas. The file needs to be readable for everyone in order to be 	visible through 'finger'. Do 'chmod a+r .plan' if necessary. You 	should realize that this information is accessible from anywhere in 	the world, not just to other people on turing.
-passwd --- 	lets you change your password, which you should do regularly (at 	least once a year). See the LRB 	guide and/or 	look at help 	password.
-ps 	-u yourusername --- 	lists your processes.
-kill PID --- 	kills (ends) the processes with the ID you gave. This works only for 	your own processes, of course. Get the ID by using ps. 	If the process doesn't 'die' properly, use the option -9. But 	attempt without that option first, because it doesn't give the 	process a chance to finish possibly important business before dying. 	You may need to kill processes for example if your modem connection 	was interrupted and you didn't get logged out properly, which 	sometimes happens.
-du filename --- 	shows the disk usage of the files and directories 	in filename (without 	argument the current directory is used). du 	-s gives 	only a total.
-df 	–k 	– Available space on all storage devices
-last yourusername --- 	lists your last logins. Can be a useful memory aid for when you were 	where, how long you've been working for, and keeping track of your 	phonebill if you're making a non-local phonecall for dialling in.
-Connecting to the outside world
+**About your (electronic) self**
-ssh 	–l username 	hostname --- 	also lets you connect to a remote host. Use rlogin whenever 	possible.
+|whoami | returns your username. Sounds useless, but isn't. You may need to find out who it is who forgot to log out somewhere, and make sure *you* have logged out.|
+|finger | of course you can finger yourself, too. That can be useful e.g. as a quick check whether you got new mail. Try to create a useful .plan file soon. Look at other people's .plan files for ideas. The file needs to be readable for everyone in order to be visible through 'finger'. Do 'chmod a+r .plan' if necessary. You 	should realize that this information is accessible from anywhere in the world, not just to other people on turing.|
-sftp username@hostname --- 	lets you download files from a remote host. This is a common method 	for exchanging files. The most important commands within sftp 	are get for 	getting files from the remote machine, and put for 	putting them there
+|passwd | lets you change your password, which you should do regularly (at least once a year). See the LRB  guide and/or 	look at help password.|
+|ps -u yourusername | lists your processes. |
-lynx --- 	lets you browse the web from an ordinary terminal. (not always 	available)
+|kill PID | kills (ends) the processes with the ID you gave. This works only for your own processes, of course. Get the ID by using ps. If the process doesn't 'die' properly, use the option -9. But attempt without that option first, because it doesn't give the 	process a chance to finish possibly important business before dying. 	You may need to kill processes for example if your modem connection was interrupted and you didn't get logged out properly, which sometimes happens.|
-Miscellaneous 	tools
+|du filename | shows the disk usage of the files and directories in filename (without argument the current directory is used). du 	-s gives only a total.|
-date --- 	shows the current date and time.
+|df –k | Available space on all storage devices |
-cal --- 	shows a calendar of the current month. Use e.g., 'cal 10 1995' to 	get that for October 95, or 'cal 1995' to get the whole year.
+|last yourusername | lists your last logins. Can be a useful memory aid for when you were where, how long you've been working for, and keeping track of your phonebill if you're making a non-local phonecall for dialling in.|
-bc 	– 	basic calculator (control-d to quit)
-man 	 - 	(manual) get help on a topic
+**Connecting to the outside world **
-top 	– 	show processes, memory and cpu (control –c to quit)
-uname 	–a 	– Name and operating system of the machine I’m on
+|ssh –l username hostname | also lets you connect to a remote host. Use rlogin whenever possible.|
+|sftp username@hostname | lets you download files from a remote host. This is a common method for exchanging files. The most important commands within sftp are get for getting files from the remote machine, and put for putting them there |
+|lynx | lets you browse the web from an ordinary terminal. (not always 	available) |
+**Miscellaneous tools	**
+|date | shows the current date and time.|
+|cal | shows a calendar of the current month. Use e.g., 'cal 10 1995' to get that for October 95, or 'cal 1995' to get the whole year.|
+|bc  | basic calculator (control-d to quit) |
+|man  | (manual) get help on a topic |
+|top  | show processes, memory and cpu (control –c to quit)|
+|uname 	–a | Name and operating system of the machine I’m on |
 You can find out more about these commands by looking up their manpages:
- man commandname --- shows you the manual page for the command
+man commandname --- shows you the manual page for the command