These commands need
to be arranged in term of their usability
1) A function letter
does not need to be prefixed with a dash ("-"), and may be combined
with other single-letter options.
2) A long function
name must be prefixed with a double dash ("--").
3) Some options take
a parameter; with the single-letter form these must be given as separate
arguments.
With the long form, they may be given by
appending "=value" to the option.
Tar ( Tape archive)
1) A function letter
does not need to be prefixed with a dash ("-"), and may be combined
with other single-letter options.
2) A long function
name must be prefixed with a double dash ("--").
3) Some options take
a parameter; with the single-letter form these must be given as separate
arguments.
With the long form, they may be given by
appending "=value" to the option.
All 4 below mean the
same thing
a) tar --create --file=archive.tar file1 file2
Note
-- c for create , f for file
b) tar -c -f
archive.tar file1 file2
c) tar -cf
archive.tar file1 file2
d) tar cf
archive.tar file1 file2
Create archive
archive.tar containing files file1 and file2. Here, the c tells tar you will be
creating an archive; the f tells tar that the next option (here it's
archive.tar) will be the name of the archive it creates. file1 and file2, the
final arguments, are the files to be archived
Other useful
addition to tar
A - Append ( you can
add a file to already present archive file)
t- List contents
(Notice T as t of LisT)
d- difference
v-Verbose
X-Extract
u- update (update a
already present file in archive if its old copy)
z-zipped
c-Compressed
tar -tvf
archive.tar--List the files in the archive archive.tar verbosely
tar -xf archive.tar
-- Extract files from archive
tar -xzvf
archive.tar.gz -- Extract files from zipped archive
Gzip (GNU zip) and Gunzip (GNU unzip)
Gzip is a
compression command and is used to compress(reduce the size of file).So running
gzip on 3 files will not combine them into one file.
In order to compress
a folder, we need to first use tar and then zip with gzip
Example -
gzip file1 file2
file3 ... this will produce 3 files ,file1.gz, file2.gz and file3.gz with .gz
extension.
Compressing a folder
tar cf – test/ |
gzip > test.tar.gz
Some File manupulating commands
awk 'BEGIN
{start_action} {action} END {stop_action}' filename
Note
1) $1 will print the
first column
2) $0 will print the
entire line
3) FS field
separator
4) OFS - Output
field separator variable
5) NF - Number of
fileds variable
6) NR - Number of
lines
awk '{print $1}'
input_file -- Prints first column
awk 'BEGIN {sum=0}
{sum=sum+$5} END {print sum}' input_file --Sum of values in 5th block
awk '{ if($9 ==
"t4") print $0;}' input_file ----notice the semicolon
awk 'BEGIN
{FS=":"} {print $2}' input_file
awk 'BEGIN
{OFS=":"} {print $4,$5}' input_file
awk '{print NF}'
input_file - tells us number of fields
awk '{print NR}'
input_file -- tells us number of records
Cut Command
Cut command in unix
(or linux) is used to select sections of text from each line of files. It can
be used as substring command by specifying the start and end position to cut.
Also it can be used similar to awk command by specifying the delimiter.
Note
d is used for
delimeter
f is used for field
posistion
c - Cut
cut -c4 file.txt
cut -c4,6 file.txt
-- this means only 4th and 6th character. It will apply to all rows
cut -c4-7
file.txt--- Start position and End position.
cut -c10- file.txt
---Start position and no end position
cut -d' ' -f2
file.txt -- Notice no c here, We are picking a field
Important point to
remember. Command always use delimeter to find end of a column
Example
logfile.dat
sum.pl
add_int.sh
cut -d'.' -f1
--- this will give
us logfile and others ( sum, add_int)
If we need to find
the value after dot. We need to reverse the string and then cut
Reverse
echo
"nixcraft" | rev
This will output
tfarcxin
Head command in Linux
