2.Utilities.ppt

Checking your Current Directory

pwd (Present Working Directory)
Displays the directory you are currently
placed in.
Example:
$ pwd
/usr/nimal
Output
Note:
pwd displays the absolute path name.

cd [directory name]
Changes the current directory to the directory
specified as the argument.
Example 1:
$ cd test
$ pwd
/usr/nimal/test

Example 2
If you need to switch to /bin:
$ cd /bin
• The command cd without an argument
switches to the home directory.
• cd .. - Moves you to the next higher level
subdirectory.

Listing the Directory Contents

ls [options] [file list]
Shows all the files in the current directory.
Options
-a All entries (hidden files, . and .. are displayed).
-x Displays multicolumn.
-F Marks executable files with * and directories
with / .
-l Long listing showing 7 attributed.

Example:
$ ls –a
$ ls –l test
Utility
Option
File name

Displaying the contents of a file
cat [Option] [file names]
Options:
-n Line numbers
-b Omit line numbers on blank lines used
with –n option
-S Single space. Reduce multiple adjacent
empty lines to a single blank line

Example:
$ cat test1 test2 test3
If you want to view files one after the other,
you can use more utility in place of cat. The
more utility pauses after displaying the
content of a file.
$ more [file names]

Creating a file
The command cat can also be used for
creating a file.
$ cat > abc
…….
……..
…….
[control + d]

mkdir [option] [directory names]
Option
-p (parent) – If the parent directory of the
directory you are creating does
not exists.
Example 1
$ mkdir test

Example 2
$ mkdir test test/test1 test/test2
Example 3
$ mkdir –p memo/letter
Parent directory
Parent directory

Deleting a File
rm [file names]
Example
$ rm abc

rmdir [directory names]
Example
$ rmdir test1 test2
Note:
You cannot remove the working directory or a
directory that contains files and
subdirectories.

Three types of users can access a file.
• Owner – (read, write, execute)
• Group - (read, write, execute)
• Other - (read, write, execute)
There are a total of nine possible ways to
access a file. All these permissions take the
general form:
- r w x r w x r w x

r indicates read permission. w indicates
writes permission and x indicates execute
permission. (ie. The file can be executed as a
program). If any of these permissions don’t
apply to a specific category, then a hyphen
(-) will occupy the respective slot.

- r w x r w x r w x
d : Directory
- : Ordinary file
b/c : I/O device
User (owner)
Group
Others

Note:
For a directory file:
• Read – read the directory (ls)
• Write – create, move, copy, remove a
directory
• Execute– search the directory (cd)

_ r w _ r_ _ r_ _ 1 mala prog 245 May 20 10:15 myfile
1- the file has only one link
mala – The file is owned by Mala
prog – The file belongs to the group prog
245 – File size
May 20 10:15 - Last modified at this time
myfile – The name of the file is myfile

• Note:
Your home directory comes with the following
default permissions set by the system
administrator:
d r w x - - - - - -
These permissions will also be acquired by
any sub directories you create.

chmod [Category] [Operation] [Permission][Filename]
Category Operation Permission
u- user + : assign
permission
r- read permission
g- group - : remove
permission
w- write permission
o – others x – execute
permission
a- all

Example
$ chmod u +x test
$ ls –l test
- r w x r - - r - -

Examples
1. Assign all categories execute permission, for the
file abc.
2. Remove the read permission of the group and
others of the file test.
3. Remove execute permission of the user and assign
read permission to the group and others of the file
xyz.
4. Assign write and execute permission for the others
in file memo.

Octal Notation –Changing Access
Permission using mode number

$ chmod [mode] [file names]
chmod also takes a numeric argument that
describes both the category as well as the
permission described in the above section.
Read permission is assigned the value: 4
Write : 2
Execute : 1

If a file has read and write permission for the
owner, then according to the above notation:
4 +2 = 6
Example
$ chmod 666 report
$ ls- l report
- r w – r w – r w -

Example:
$ ls -l memo
d r w x r – x r - - 1 nimal mine 20 Feb 12 21:14 memo
1. According to the output shown above, is
memo a file ?
2. Does the group have execute permission?
3. How can you give the others write permission?

cp [options] [source file] [destination file]
Creates an exact image of the file on disk
with a different name.
If the destination file does not exists, it will
be first created before the copying takes
place. Else, the file will be overwritten.

Option
-i (interactive): Warns the user before
overwriting the destination file
Example
$ cp abc xyz
$ cp -i abc xyz

mv [option] [existing file name] [new file name]
mv [option] [existing dir name] [new dir name]
The mv command renames a file/directory. The
command does not create a copy of the file. It
just renames the file. If the destination file
exists, then it will be overwritten.

Option
-i (interactive): Warns the user before
overwriting the destination file
Example
$ mv memo letter

Moving a file
mv can be used to move a group of files to a
directory.
Example
$ mv test1 test2 test3 test4 test
Directory
These could be files, directories or both

lpr [options] [file names]
Example
$ lpr report memo letter
lpq – provides status information about jobs
currently in the printer queue.
lprm – removes files from the queue.

Option:
-h : Skip printing the header page with your
login name.

$ uniq [option] [file name]
Option Description
-c Count each line with number of
occurrences
-d Duplicated lines, display only lines
that are repeated
-u Unique lines, display only lines that
are not repeated

Example:
$ cat sample
abc
abc
xyz
pqr
pqr
pqr
Lines repeated
Lines repeated

1. $ uniq sample
abc
xyz
pqr
2. $ uniq –c sample
2 abc
1 xyz
3 pqr
No. of
repetitions

3. $ uniq –d sample
abc
pqr
4. $ uniq –u sample
xyz
Only the lines that were duplicated
will be displayed
Only the lines that were not
Duplicated will be displayed

cmp command can be used to find out
whether two files are identical in all respect
so that one of them can be deleted.
Example:
$ cmp test1 test2
test1 test2 differ: char 10, line 5
$_

The two files will be compared byte by byte
and the location of the first mismatch will be
displayed on the screen. When the command
is used without options, it does not bother
about possible subsequent mismatches, but
will abort with the message shown above. If
the two files are identical, them cmp will
display no message.

-l option
Example:
$ cat memo1
abc
xyz
$ cat memo2
abe
wxy

$ cmp –l memo1 memo2
3 143 145
5 170 167
6 171 170
7 172 171
Character number
Octal representation
of characters

Example:
The file grocery_list consists of four fields. The
fields are: item, supplier, supplier address and
price/unit.
Item Supplier Address Price/unit
Sugar Sweetprod Ltd Kandy 45.00
Butter SLExporters Colombo 135.00
Carrots ABCFarms.Ltd Nawalapitiya 90.00

a. How can you create the file grocery_list?
b. How can you create a copy of the file grocery_list with name
grocery?
c. How can you tell whether the file grocery_list is the same as
the file grocery?
d. How can you see the grocery_list entries that are repeated?
e. What is the command to print the file grocery_list
f. What is the command to count the number of lines of the file
grocery_list
g. What is the command to view the details of the file grocery
page by page
h. What is the command to create the parent directory STORE
and two sub directories S1 and S2
i. How can you move the files grocery_list and grocery to the
directory STORE

j. How can you confirm that the two files has been moved to
the directory STORE?
k. What is the command to rename the file grocery_list to
grocery?
l. How can you move to the subdirectory S1
m. What is the command to return back to the direcoty STORE
n. What is the command to delete the file grocery?
o. What is the command to delete the directory S2

Using echo to display text on the
terminal
Example:
echo “This is a test message”
This is a test message
$_

Line, Word and Character
counting

$ wc [Options] [File name]
Option Description
-c Count the number of characters.
-l Count the number of lines.
-w Count the number of words

Example:
$ cat memo
This is to test the wc command
$ wc memo
1 7 30 memo
Note:
A character includes all spaces, tabs and
newlines
lines
words
characters

Login details
who - Displays a list of the users currently
logged in.
Example:
$ who
Nimal123 tty01 Aug 12 10:32
Mala342 tty02 Aug 12 10:40

Using man to display the system
manual
The manual utility displays pages from the
system documentation on the terminal.
Example:
$ man who

You should not use any of the special
characters in a file name or as regular
characters.
& ; * ‘ ” [ ] ( ) $ < > { } # ? /
In addition % ! and ~ are special characters
to the C shell and the Korn shell.

What will happen if special characters are
used as regular characters…
$ echo Hello
Hello
What will be the output for the following?
$ echo *

Quoting Special Characters
To use a special character as a regular
character, you can quote it. To quote a
character precede it will a backslash ().
Example:
rm presentation*

Wild card Significance
* Matches any number of characters
including none.
? Matches a single characters
[ijk] Matches a single character either i, j or k.
[!ikj] Matches a single character which is not
an i, j or k.
[x-z] Matches a single character which is
within the ASCII range of the characters
x and z.
[!x-z] Matches a single character which is not
within the ASCII range of the characters
x and z.

Example:
What command will display the contents of
the current directory whose names start
with the character ‘a’ and end with a period
(‘.’) followed by any one character followed
by either the number 2, 4 or 6?

Using mail to Send and Receive
Electronic mail

I. $ mail nimal
subject: Test message
This is a test message
……
…….
[control + d]
II. mail nimal@…..
To read you mail, run the mail utility
without a user name.

Using diff to compare two file

This command can be used to display file
differences. Unlike cmp command, it tells
you which lines in one file has to be changed
to make the two files identical.
Ie. the output will tell how to make the first
file equal in contents to the second file.

$ diff [Option] [File 1] [File 2]
$ diff [Option] [Directory 1] [Directory 2]
Compares all files in directory 1 with files in
directory 2 that have the same name

Options:
-b (Blank): This option causes diff to ignore
blanks,tabs and spaces.
Example:
$ cat report1
bbbb
cccc
$ cat report2
aaaa
bbbb
cccc

$ diff report 1 report2
0a1
>aaaa

2.Utilities.ppt

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2.Utilities.ppt