Commands in Linux Presented By QuontraSolutions

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Linux Commands

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• QuontraSolutions
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Topics

• head
• tail
• link
• tar
• gzip and gunzip
• touch
• diff

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• head command

Displays the first ten lines of a file, unless
otherwise stated. Syntax head -number -n
number filename Example head -15
myfile.txt It displays the first 15 lines of
myfile.txt .
-number Number of lines to display
-n number Number of lines to display
filename Desired filename
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• head command

Displays the first ten lines of a file, unless
otherwise stated. Syntax head -number -n
number filename Example head -15
myfile.txt It displays the first 15 lines of
myfile.txt .
-number Number of lines to display
-n number Number of lines to display
filename Desired filename
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• tail command

• Displays the last ten lines of a file, unless
  otherwise stated.
• Syntax
• tail -n number -l -b -c -r -f file

-n number Number of lines to display
-l Units of lines.
-b Units of blocks.
-c Units of bytes.
-r Copies lines from the specified starting point in the file in reverse order.
-f Displays the last 10 lines and then update the file as new lines are being added.
filename Desired filename
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• link command

Creates a link to the file or directory. Syntax l
n -f -n -s -i source destination
-f Forced to create a link.
-n Does not overwrite existing files.
-s Creates a Symbolic link.
source Desired filename
destination Destination filename
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• Example
• ln s f1 home/myfiles/f2
• Creates a symbolic link between file f1 to file
  f3 of myfiles directory.
• Represented as ?
• View the Link using
• ls l
• Remove the link using rm command.
• rm r f1.

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• tar command

• Used to group set of files in to ma single file.
  It is called Archive file.
• Syntax
• tar -c -t or -v -x -f filename
  archivefilename
• It has .tar extension.

-c Creates an archive file.
-t or -v Lists archive file content.
-x Extract or de archive an archive file.
filename File to be archived
archivefilename New name for archive file.
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• Examples
• Create an archive file
• tar vcf dir1 myarc.tar
• It creates archive file myarc.tar which has all
  files of directory dir1.
• 2. Dearchive an archive file
• tar xvf myarc.tar
• All files in dir1 are no more grouped, they are
  separated.

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• gzip and gunzip

• Used to compress and decompress the file
  respectively.
• Syntax
• gzip -f-d filename.
• gunzip -f compressedfilename.
• It is with .gz extension.

-f Compress forcibly.
-d Decompress the compressed file.
filename File to be compressed.
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• Examples
• Compress the file.
• gzip f f1.
• Compresses the file f1 and is represented as
  f1.gz.
• 2. Decompress the compressed file.
• gzip d f1.gz or gunzip f f1.gz
• File f1.gz is decompressed to file f1.

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• touch command

Used to change the timestamp of a file. It is
also used to create multiple files at one
shot. Syntax touch t -a-m -r
reference-file filename
a To change access time
m To change modified time
-r Refer the timestamp of another file
filename Required filename
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Use Stat command to know the Timestamp. stat
f1.c (sample output) Access 2010-11-01
203558.000000000 0530 Modify 2010-11-01
203558.000000000 0530 Change 2010-11-01
203558.000000000 0530 Format for touch -t
is YYMMDDhhmm.ss
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• Examples
• Create multiple files at once.
• touch file1.txt file2.txt file3.txt
• 2. Change the access time of a file.
• touch t -a 08210820 file1.txt
• Access 2010-06-15 133000.000000000 0530
• Modify 2010-08-21 082000.000000000 0530
• Change 2010-11-01 204505.000000000 0530

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Same way we can change the modified time of a
file using -m along with -t 4. Refer the
timestamp of another file than the current
time. touch -r file4 file5 file 5 uses the
timestamp of file4.
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• diff command

It is used to find differences between two
files. Syntax diff options file1
file2 Options
a Treats all files as text and compare them line-by-line.
y Use the side by side output format.
w Ignore white space/blank space when comparing lines.
i Ignores Case.
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Let us have two files, file1.txt and file2.txt
as follows
file1.txt file2.txt
LINUX TESTgoodmorning with great thoughts Lead india LINUX TESTGOODMORNINGwith   great   thoughts
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Examples 1. Compare the files side by side,
ignoring white space.diff -by file1.txt file2.txt
LINUX TEST
LINUX TEST hscripts.com

HSCRIPTS.com with great thoughts
with great thoughts
Lead India
lt 2. Compare the files side
by side, ignoring Case.diff -iy file1.txt file2.t
xt LINUX TEST
LINUX TEST hscripts.com

HSCRIPTS.com with great thoughts
with great thoughts
Lead India
lt
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Thankyou