File Commands Of Linux Ii

Command Purpose Output / activity taken
$ cat file1 to see the contents of the file1 It is a fun.
Suppose file1 contains the text: You are encouraged to work
It is a fun. You are encouraged to with the Linux.
work with the Linux.
$ more screen by screen view of file if it is It is a fun.
lengthy You are encouraged to work
file1 with the Linux.
$ cat file1 file1 sends the output to the standard file1 is copied into file2 also
output but the redirection operator
> file2 (>) sends
(redirects) output of the standard
output to the file2. The redirection
operator (>) prevents the output
from going to the screen.
The part after > is executed first.

If file2 does not exist, file2 will be
created and the contents of file1 will
be copied into file2.
if the file already exists, then contents
of file2 will be destroyed and made
fresh and then contents file1 will be
copied
Then contents of the left hand side
file namely file1
is sent to the standard output. The
output of the standard output is
taken
as the input for file2. In short the
contents of the file1 is copied into
the
file2.

$ cat file2 To see the contents of the file2 It is a fun.
You are encouraged to work
with the Linux.
cat file1 > empties the file1 (Since RHS & LHS file1 content will be nothing
name are same). So the command
file1 fails.
You can set the noclobber feature to prevent overwriting an existing
file by the redirection operation. In this usage, overwriting of the existing file will fail.
$ cat file1 To overcome the difficulty of appends the contents file1 to
overwriting the existing file append the contents of file2.
>> file2 (>>) operator is used. The append
(>>) operator adds the contents of
the file, appearing left side of “>>”
operator to the file appearing to the
right side of the same operator, at
the end of the existing material

page 1

$ cat The cat command without any expects data from the
argument takes the input from the standard input.
standard input After receiving it displays
immediately in the next line
*** ***
The entered message is taken to the SRM
standard input from SRM
the buffer, which is directed to the Chennai
cat command. Since there is no Chennai
redirection operator, cat displays the
message on the screen
After completion inform it to
computer by pressing ctrl+D keys in a
separate line
Note: Data can be compared to the water in a dam. Buffer is like a dam where water is
collected before sending for irrigation (the standard output) when there is copious supply of
water (data). It stores and sends water (data) in more orderly manner when there is a
request for water or when the dam is full. Ctrl+D character is the end-of–file character for
Linux file.
Combination of the cat command with output redirection operator (>)
$ cat > Here LHS name is not mentioned
So from standard input i.e keyboard
file3 input is received and redirected to
file3
On completion in a new line press
ctrl+D.

page 2

Combination of the cat command with input redirection operator (<)
$ cat < To make the cat command to get Displays contents of file3 on
data from the file3 (not from the screen
file3 keyboard)

Standard input to receive data from
files also.

This is made possible by the
redirection input operator.

cat < file3 If the standard input is to be file3 contents are redirected
redirected to receive its data from to file4
> file4 file3, and the standard output is to
be redirected
to place its data in file4,
Piping operator(|) is used to redirect output of one command to another command
whereas redirection operator used to redirect output of one file into another file.
The piping symbol is the vertical bar “|” (key before to backspace key).

$ cat file3 to have the contents of file to be
printed. The cat command gets
| lpr contents of a file and sends it to the
standard output. The output of cat is
piped to lpr (line print i.e the printer
connected to the system currently).

Here cat is one command and lpr is
another command

$ cat | lpr User has to type in the input expects data from the
standard input.
After receiving it prints in the
While completion press ctrl+D. printer immediately in the next
The typed matter is printed in the line
current printer

page 3

$ cat –n contents of file3 is sent to the printer Content of file3 is printed with
(each line will be numbered) their line number
file3 | lpr

The cat command with the option –n
sends the contents of the file3 to the
standard output after numbering
each line.
If the file is lengthy and if you use the cat command, you can see only the last page. To
overcome this difficulty the command more is used
$ cat file3 | more The contents will be displayed screen page by page contents are
by screen, by getting the displayed
confirmation from the user
$ cat –n file3 | more . page page display with line page by page contents are
numbering of each line displayed with each line
numbers
$ cat –n displaying more than one file page
by page with line numbered for
file1 file2 more than one file
file3 | Note: Comma should not be used
more. between file names; only blank
space/
spaces should separate them.
Sort command helps in arranging the contents in alphabatical order.
$ sort sorts each line of the given file file3 is sorted & sent to
alphabetically and sends the sorted monitor.
file3 | version to the standard output.
more
$ sort You can send the sorted output to file3 is sorted & displayed
more, cat –n, lpr or to any of the screen by screen
file3 | cat suitable combinations of these. file3 is sorted & sent to printer
-n | more
$ sort
file3 | cat
-n | lpr

page 4

The tee command copies the standard output to a file. It takes as its argument the name of
the new file to which the standard output is copied. It seems when the standard output sees
the tee command; it will split into two copies. Normally, one of them is redirected to the file
appearing after the tee command and the other goes to the screen. The following
example not only copies file5 to file6 but also displays the contents of file5 on the screen.
$sort file5 The sorted contents of the file can be sorted o/p of file5 is copied
copied into another file and also can into file6 & displayed on
| tee file6 be displayed on the screen. monitor.
*** file5 contents will not be affeted
***
$ sort
file5 | tee "

sfile5
$ sort sfile5 created (sorted content) and The output is :
displayed on screen, Ashok
file5 | tee and printed Chandran
Malar
sfile5 |
lpr
$ sort sfile5 created (sorted content) and The output is :
displayed with number on screen, 1 Ashok
file5 | cat and printed 2 Chandran
3 Malar
-n | tee
sfile5 |
lpr
Copying file - to copy the contents of one file into another in a straightforward manner - use
cp command ( one of the command)

Syntax : $
cp
[options]
<source
file/s>
<destinatio
n
directory/f
ile>

page 5

$ cp file1 The cp command copies the file1 contents are copied into
contents of source file after creating file6
file6 destination file. If the destination file
already exists then the existing file is **** be careful in giving
destroyed then a new file with destination file name ****
same name is created

$ cp -i -i option gives warning about $ cp -i file1 file2
overwriting of destination file (if exists) overwrite file2 ? n $
file1 file2

If files are not in the current directory, then the full path should be given. If you want to
establish a link between file1 and file2, you should replace –i by –l.
$ cp -r copies a directory to another copies all the files and sub-
directory directories of the alpha
alpha directory to the alpha1
If directory alpha1 exists already, all directory recursively.
alpha1 the contents are put inside the
directory. If alpha1 des not exist it will
be created and all the files and the
sub-directories are stored. This alpha1
is created under the current working
directory.
There are two more options -s and -v. The option -s creates a symbolic
link and the option -v (stands for verbose) explains in detail, what is
being done.
Removing Files
To delete files or directories the rm command is used. This is superior to rmdir.
rm can be employed even when the directory is not empty, whereas the rmdir can be
employed only when the directory is empty
$ rm file1 removing files and folders file1 and file2 are deleted

file2
$ rm -r to delete even the subdirectories removes alpha1 directory
along with its subdirectories.
alpha1
$ rm -i gets confirmed and deletes. removes only after
confirmingalpha1 directory.
alpha1
$ rm -v alpha1

page 6

Wildcard entries & filename arguments - giving clue by providing partial information
* stands for any number of characters
? fixes the number of characters. i.e ? Is = single character
[ ] gives you a set of characters to search the file with them

$ ls main.c fact.c swap.c char1
char2.ex doc1 doc2

$ ls ch* char1 char2.ex

$ ls *.c main.c fact.c swap.c

$ ls char? While the first four characters are Char1
fixed, the last one may be any
character including numbers
Note: char2.ex will not be displayed,
since the length of char2.ex is
greater than 5 characters.

$ ls doc1 doc2

doc[12]

doc[1-5] search for doc1, doc2, doc3, doc4,
doc5. doca, docb, docc, docd,
doc[a-g] doce, docf, docg

page 7

Moving and Renaming the Files.
The mv (move) command is used
Role of mv command
1. to move a file or directory from one location to another.
2. to change the name of a file or a directory.

Moving a file from one location to another is different from copying a file in that no file
is created while moving a file.
Syntax: mv [options ] <source> <destination>

mv temp renaming the temp directory is renamed
into a temporary directory.
temporary
$ mv moving file1 of current directory is
moved to the location
file1 /home/ilamathi/personal/
/home/ilama
thi/persona
–i, -v and –f options along with this type of commands

page 8

Viewing the System Date and Time
$ date Mon Jan 05 11:41:12 EST 2009

The day, the month, the year, the date, the time in hours, in minutes and
in seconds can be referred to, as shown below.
$ date “+ Displays day of month in digits 5

%d”
$ date “+ Displays Month of the year (in digits) 1

%m”
$ date “+ Displays Year(last two digits) 9

%y”
$ date “+ Displays Date as mm/dd/yy 01/05/2009

%D”
$ date “+ Displays Time as HH:MM:SS 11:43:14

%T”
$ date “+ Displays Hour(00 to 23) 11

%H”
$ date “+ Displays Seconds(00 to 59) 43

%S”
$ date “+ Displays Minutes(00to 59) 14

%M”
$ date “+ Displays Abbreviated weekday(sun MON
to sat)
%a”
$ date “+ Displays Abbreviated month(jan to JAN
dec)
%h”
$ date “+ Displays Time in the AM/PM notation 11:43:14 AM

%r”
Note: With the help of the above options, the SA can change any part of the date
command.

page 9

File Systems: mount and umount
The files themselves are organized into one perfect tree of directories beginning from the
root.
Although the root may be located in a file system on your hard drive partition, there will be
a path name to files located on the file system for your CD-ROM and floppy.
The floppy or even CD-ROM completely dependent upon the root directory.
If you want to access the contents of the files, in the file system, you should start from the
root directory.
For that you have to connect the sub-tree to the main
tree.
Until it is attached, you will not be able to access the files on your floppy disk.
This applies to all the storage mediums unless they are connected already.
Even the file system on your hard disk partition has to be mounted with a mount command.
But the system takes care of this activity.

Establishing the connection between a file system on a storage device and your main
directory tree is called mounting the device. This is done with the mount command.
Only the root user SA can access this command (Drawback)
The syntax for the mount command is :
# mount device destination

Device means the device files which are locted in /dev directories
/dev/fd0 refers to first floppy drive

/dev/fd1 refers to second floppy drive

/dev/hda2 refers to hard disk second drive

# mount mounting first floppy drive in the
mentioned destination
/dev/fd0
/destinatio
n

page 10

Disconnecting a file system on a storage device from your main directory tree is called
Unmounting the device. This is done with the umount command.
Only the root user SA can access this command (Drawback)
The mounted file systems should be unmounted whenever
1) before you shut down your system
2) before you want to replace a mounted file system with another
Syntax: # umount device (or destination )
# umount unmounts the floppy drive

/dev/fd0

page 11

Keys used for editing text in the command
line
alternative key
Activity Key
combination
moving one character to the
ç ctrl + B
left
moving one character to the
è crtl + F
right
Back space
Erasing characters and Delete ctrl + H - backspace
key

Deleting entire line ctrl + U

We can enter more than one command in the same line but we
should separate them with a semicolon ( ; ).

We can also enter only one command in several lines by typing a
backslash in each line.

Example

$cat file1; sort file1; cp -i file1 file2

$cp
-i
file1
file2

Linux commands for IX std

Command Purpose
pwd Present Working Directory - to be seen
cd to change Directory
cd .. to move to parent directory
cd /usr/local/lib to move to some other directory named to be /usr/local/lib
ls to list files of current directory
ls /usr/local to list files of mentioned directory /usr/local
ls a* listing files whose names are starting with letter a
listing files whose names are starting with letter a and following
ls a??
which only 2 charactyers which may be anything
listing files named subject and ending with any numbers from
ls subject[0-9]
0-9
ls -d listing only directory names
ls -l long format listing
ls -m listing names separated by commas
ls -a listing all files including hidden files
ls -c listing files column wise
ls -F identity directions, links and executables
ls -R list Directory contents recursively
ls -S listing by sorting files by size
ls -color use color to identify files
gets i/p by keyboard
cat
displays on monitor
cat >nineth
and stores on file named nineth
cat nineth displays the contents of file named nineth
cat file1.txt file2.txt file1.txt and file2.txt combined and stored into file3.txt
> file3.txt
cat fil1>>file3 file3 contents are appended with the fil1 contents
mkdir srm creates the directory namely srm
copies srm into another name rms
cp srm rms if rms already exists then overwrites the old content with new
entry
cp -i srm rms
if rms already exists then gets confirmation before overwriting
cp -r dir1 dir2 Copies whole directory dir1 into another name dir2
mv abc marks renames abc into marks
mv -I abc marks gets confirmed and then replaces
mv marks /tmp moves the file marks to the directory tmp
cp -b student makes the student file to be the back up in the name marks
marks back up files ended with ~ symbol
rm student deletes the file student
rm -I students gets confirmed and then deletees
rm -r tmp deletes the directory
locate file* shows the directory names of files named file*
whereis man displays manual page for man command
chown to change ownership
chmod to chane the permissionto individual files
Only owner has rwx permission others
chmod 644 file1.txt
read only
chown arasu tiger.html to change the ownership toarasu for tiger file
Helps

Command Purpose Command Purpose

listing files named subject and ending
pwd Present Working Directory - to be seen ls subject[0-9]
with any numbers from 0-9

cd to change Directory ls -d listing only directory names

cd .. to move to parent directory ls -l long format listing

to move to some other directory named to
cd /usr/local/lib ls -m listing names separated by commas
be /usr/local/lib

ls to list files of current directory ls -a listing all files including hidden files

to list files of mentioned directory
ls /usr/local ls -c listing files column wise
/usr/local

listing files whose names are starting with identity directions, links and
ls a* ls -F
letter a executables

listing files whose names are starting with
ls a?? letter a and following which only 2 ls -R list Directory contents recursively
charactyers which may be anything


ls -S listing by sorting files by size cp srm rms if rms already exists then overwrites
the old content with new entry

ls -color use color to identify files cp -i srm rms if rms already exists then gets
confirmation before overwriting

gets i/p by keyboard Copies whole directory dir1 into
cat cp -r dir1 dir2
displays on monitor another name dir2

cat >nineth mv abc marks renames abc into marks
and stores on file named nineth

cat nineth displays the contents of file named nineth mv -I abc marks gets confirmed and then replaces

file1.txt and file2.txt combined and stored moves the file marks to the directory
cat file1.txt file2.txt > file3.txt mv marks /tmp
into file3.txt tmp

makes the student file to be the back
file3 contents are appended with the fil1 cp -b student
cat fil1>>file3 up in the name marks back up files
contents marks
ended with ~ symbol

mkdir srm creates the directory namely srm rm student deletes the file student


rm -I students gets confirmed and then deletees

rm -r tmp deletes the directory

shows the directory names of files named
locate file*
file*

whereis man displays manual page for man command

chown to change ownership

chmod to chane the permissionto individual files

Only owner has rwx permission others
chmod 644 file1.txt
read only

Helps to change the ownership toarasu
chown arasu tiger.html
for tiger file

File Commands Of Linux Ii

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