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Panther Moderns: UNIX and file controllers
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* *
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* Unix and its file controllers *
* *
* Another Modernz Presentation *
* *
* by *
* Digital-demon *
* *
* (C)opyright April 2, 1991 *
* *
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The Modernz can be contacted at:
MATRIX BBS - Sysops: Wintermute & Digital-demon
(908) 905-6691
The Villa Straylight - Sysop: Tal Meta
(908) 830-7960
The Church of Rodney - Sysop: Tal Meta
(908) 830-7786
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UNIX SYSTEMS
Among the multitude of operating systems one is the most commonly used, and that is UNIX. UNIXs varied array of look alike and modifications such as zenix and other 'nix variations. These ytm ae one feature that makes them stand together and that is the multiuser/multitasking envirnmnt HweerI wish to show the files and what commands are used to manipulate them.
First you must know that the multi-tasking and multi-user environment , which means that it cane more than one action or user concurrently, is done by the operating system. The operating sytmuiies a time-sharing routine, by maintaining the list or queue (which you can understand by radngbok n ata structures) of tasks to be done, and shares the time among the jobs waiting to beproessd. Thetim frame of processing given to each task is so small the user believe the system o beprocssin thejobssimultaneously.
Each time a user logs into the system they are associated with their own particular directory, 'home' directory. This is not the root of other operating systems. Each users has their own 'hm'drcory which is where the pointer for the working directory originates instead of the root ofmot thr peating systems. UNIX follows the
hierarchical directory system as do most other operating systems. It also can only manipulate data the primary storage, the memory, and automatically handles the movement between the secondary,ds,adthe primary storage system.
Within the hierarchical directory structure the operating system keeps track of the file owner,ast modification date and time, the location of each file, and the size in bytes (or characters fdt ithin the file. They are kept in a format like this:
/-defines if a directory or not (a - in place of a letter
| means a no, s means special file)
|
|/-these three characters define the file owner modes
|| the (r-read, w-write, x- execute)
||
|| /-these three characters define the users in the same
|| | group as the owner
|| |
|| | /-these three characters define the other users of
|| | | the system
|| | |
|| | | /-total # of blocks (1024 bytes)
|| | | | /-owner name (account name)
|| | | | | /-group owner name
|| | | | | | /-how many characters
|| | | | | | |
|| | | | | | | /-last modification time
|| | | | | | | |
|| | | | | | | | /-file name
|| | | | | | | | |
|| | | | | | | | |
drwxr-xr-x 3 neal DP3725 80 March 10 22:12 UNIX
The top of the hierarchical structure is called the root. The root directory and all associateirectories are called a file system. A hierarchical system may appear as following:
root
|
|
--------------------
| |
Jim demon <-these accounts are user's home
|
----------
| |
docs homework
| |
------ ------------
| | | |
txt opsys calculus assembly
Subdirectories within a path are separated by the backslash (/) character. This character also the path will define how far from the root the operating system must travel. Within the hieracia tucture and the notation conventions a single period (.) defines the current working direcor, ndtw priods (..) define the root. Note that within the UNIX operating system the root diretor ma hae anam. You access files within another directory by specifying the whole path name, uch s th fil UNI witin the opsys directory is called by the path /demon/docs/opsys/UNIX, remembr tha withn UNI capials ad lowercase are recognized as different. You may have files named: UNX, UNi,UNIx,etc, wthin te samedirectory and have them all recognized as seperate entities.
UNIX is an interesting operating system as the standard comes with three text editors, and theia vast number of other text editors that are nonstandard formats but also quite common within sse. nortunately because there are so many different version of UNIX and its editors and other cmmnd, an o those text editors have security risks within them, holes in the permissions, and oter uppsedy scurty measures, this is cause by the lack of full understanding of everything withi theUNIXsystm byany ne author/programmer (Midnite Raider 5.)
The editor that seems the easiest to use, among programmers from other operating system is the e editor. It is used in the format ed filename. It is similar to most other operating systems ieeiors, quite similar in fact to DOS's edlin command.
$ed names
Commands with ed Description of action
P Display the prompt (which within the ed
Command appears as an asterisk (*)
*1n Print line 1 (note the * is the
prompt).
*1,3n Print lines 1 through 3.
? Produced when a command is in error,
such as 2,8n when there are only 7
lines.
*h Prints out explanation of errors, should
be used after receiving an ? to find
out what the error is.
*H Automatically prints out all error
messages after this is used. It is
suggested that this is used right after
the P command is given.
*1d Delete line 1
*1a Append after line 1
. used in conjunction with the append to
tell the operating system when the
append is to be terminated.
*1,$n Display entire file.
*3,$d Delete line 3 through the end of file.
*$a Append at the end of the file.
*/test Finds line containing the string "test"
Repeating the string will find the next
line that contains the string "test" if
it exists.
*.,$n Lists from the current line to the end.
*s/brick/tear Changes the string "brick" to "tear" in
the example. Only the first term found
if more than one on the same line.
*s/,/;/g Would change all the "," to ";" on the
current line.
*1,$s/,/;/g Would globally change. Which means it
would search through and on every line
change all the "," to ";"
*q Quit. Finish editing, however it will
not save the file.
*w Write changes to the file defined upon
entering. It save the data/text.
*w demon Writes the changes to the file demon.
Line specifiers
. current line
$ last line of buffer
n nth line where n is an integer
+n n lines from current(or + :1 line,++:2)
-n n lines back (- : 1 back, -- :2)
More powerful than the ed command is the Vi text editor. The "vee-eye" screen editor allows th itself to appear on the screen and to allow the user to freely move about it. However becauseo hsrason inexperience users fine this to be too much of a shock to comprehend. The editing itel i sow o the screen, as the operating system copies the existing file to the buffer, and the i mkestheterina screen a "window" showing a screens worth of the file from the buffer.
vi [option(s)] [file(s)]
options Descriptions
-rfile Attempts to recover file after the editor
or system crashes. This will not work if
the buffer is overwritten.
-l Sets the LISP mode
-wn Sets the window, screen size, to n number
of lines.
-R Sets the editor to read-only mode. This
means the user can move around the text
but editing commands are disabled.
+command Use of editor command before the regular
editing process.
Commands within the vi description
a Append to file after the
cursor. (Hit the escape key
after all appending commands
are done.)
A Append to the file at the end
of the current line.
I Insert to file at the beginning
of the line.
i Insert to file before the
cursor.
o Open/add a new line below the
current line the cursor
inhabits.
O Open/add a new line above the
cursor.
R Replace or over-type text.
s Substitutes for character under
cursor.
S Substitutes for whole current
line.
c Changes the indicated text.
C Replace to the end of current
line.
d Deletes the indicated text.
D Deletes to the end of the line.
VI editor commands Description or meaning
dd Deletes current line
u Undo last delete.
x Deletes under cursor.
X Deletes in front of cursor.
y Make a copy "yanks" the
indicated text.
Y Yanks current line.
-----------------------------------------------------------
k Move the cursor up one line.
n Move the cursor to the left.
l Move the cursor to the right.
j Move the cursor down one line.
2k Move cursor up two lines.
kk Move the cursor up two lines.
<digit><j,k,l,or n> Moves the cursor the specified
direction by the number of
spaces equal to digit.
-----------------------------------------------------------
ZZ Save to file and quit.
^D <control-d> down 1/2 screen
^U <control-u> up 1/2 screen
/word <carriage return> String search for "word."
?word <carriage return> String search for last "word."
w Go to next word.
e Go to end of line.
b Go to previous word
dw Delete one word
d$ Delete to end of line.
cw Change word
-----------------------------------------------------------
:q Quit and don't save any changes
:w Write changes but do not quit.
:q! Discard changes to file.
:1 <carriage return> Jump to line 1
:s/a/is/<carriage return> Change "a" to "is"
;$ <carriage return> Go to last line
:set number<carriage return> Turn on line numbering.
Once files have been created with either of those two methods there are many commands the operatstem allows you to use to view and maneuver the files within the system.
To list you files in your current directory, which you would probably like to do after completeing yation, or your modification of an exiting file, you would probably like to see the file's size. oyuwuld issue the ls command, which at the default ($) prompt would look like this : $ ls
And it would display all the file names in the current directory, or if a: $ ls /pathname is issuedthe dirctory of files within that path are displayed. A $ ls -l in either of the formats will ilyalthe file parameters within the directory as explained previously in detail.
Now maybe after listing your files in your currently directory, and assuming you are all new toand have only you working directory, which is also your home directory. You will want to issueamdrcmmand, make directory, which should include the full path name.
In this case you will make a directory called TXT and a directory called OPSYS. $ mkdir ./TXT in tse I created the directory TXT one down from the current.
Now assuming I have created those two subdirectories below my current, which is the "home" direin this case. And I have a bunch of files within the home direcotry which I would like to movet h iectory. I would issue the $ cp oldfilename newfilename The cp is the copy file command. An i Iwihtto move a file to another directory I just define the newfilename with its full path. Coyin fo on diectory to another direcotry, neither within the current just means both files mut bedefied wth te ful pathname.
However A lazy user can get around using the full pathname in the firstfilename as long as priohe command they had issued the CDPATH command with the path to be used within. This command whc a eset up like such: $ CDPATH=.:..:$HOME in this case a cd command or a copy command will sarh helit f direcotries in trun until the desired subdirectory is found or the list exhausted. Witin he istof his one is (.) for the current directory, (..) for the parent or root directory,and HOMEfor he hme drectory. Each directory or subdirectory is separated by the (:) .
Now you come upon some files you don't remember what they are because you named them funny. Fiu would probably issue a concatinate command. Sure that sounds like a joining command and it i fue n that format. By typing: $ cat filename You can display the contents of
filename on the screen in normal format. If you wish to see commands within a file that are "unprin the command $ cat -v filename will display most "unprintable" characters. They will appear wihacrtbefore them. An example is if a control-d is used within the file, a ^d will appear. If ouisueth cmmand as $ cat filename1 filename2 one file will be listed right after the other. Ths i usfulwhe inthe process of printing a larger number of files, just uses the pipe to the priner, r ifa $ at flenae1 filename2 > filename3 is issued then the two files are listed in sequenc and aved n fil 3. oweve if file 3 is the name for either of the previous files the cat comman wipesthe fie clea befor anythng is saved into it.
Now that you have figured out what the strnagely named program is, maybe it would be better to the file to something you can remember. With a single use of
$ mv <old name> <new name> you have solved you dilema. Or if someone else is useing the same accou you don't wish to confuse that user, you may use the $ ln <old name> <name> command to link orasg nadditional name which can be used to define the file. Thereby creating an alias for you psk fle r f you find that after listing the file you can not figure out a use for the file and ishto
remove it, issue the $ rm command, rm can be followed by as many names as you wish or you could addpecial characters to perform the job if names are similar.
Now suppose you want other people to use this file. Or you have a file copied from another useu will probably want to or need to redefine the permissions. There are quite a few commands readn h permissions. First before you get the new file from a friend or transfer a file to them,yo soud sse the change owner command, which can only be done by the owner or the system operato.
$ chown newowner file(s). Then if you wish to change the group name of the file a simple 'chgrp' cois issued in the form $ chgrp (newgroupname) (file(s)) which tells which group has permission t ceste file under the group parameters, needless to say it is not a commonly need command, but orh noin jst in case.
However you are the kind of person that doesn't wish those other people within the group to foond and modify your hard work. But you would like to show it off so you want the group to see i. htd you do? Well how about issuing the change file mode command. This command is the end al o flepemisions alterations. It can be used
in the format of: $ chmod (absolute-mode) (file(s)) or in the form: $ chmod (symbolic-mode) (file In either format this command can be used to set the permissions for either a file or a whole ietr.
Absolute mode Meaning
4000 Set the user ID upon execution.
2000 Set the group ID upon execution.
20#0 If # is 7, 5, 3, or 1, then set the
group ID. If the # is 6, 4, 2, or
0, then enable file locking.
1000 Reserved
0400 Owner has read permission.
0200 Owner has write permission.
0100 Owner has execute (search)
permission.
0040 Group has read permission.
0020 Group has write permission.
0010 Group has execute permission.
0004 Others have read permission.
0002 Others have write permission.
0001 Others have execute permission.
For example if 0644 is given as the absolute value then the following are enabled: 0400 (owner ad permission), 0200 (owner has write permission), 0040 (group has read permission) and 0004 (ohr aeread permission).
Symbolic mode consists of three parameters within the command. They are the "who" the "operato the "permission string".
Symbolic mode Meaning
Who
u User
g Group
o Others
a All which takes the place of
defining as ugo, this is the
default of the who parameter.
Operator
+ Add these permissions to what
already exists.
- Remove these permission from what
already exists.
= Assigns absolutely the indicated
permissions. Anything mentioned
and those things not mentioned are
also affected.
Permission string
r Read
w Write
x Execute
s Set ID
l Manadatory file lock during use.
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