1 : How to ignore some words while doing search using grep in UNIX

grep Exception logfile.txt | grep -v ERROR

This grep command example will search for word “Exception” in logfile.txt and print them but since we have piped out of first grep command to second grep command which will exclude all lines which match world “ERROR”.

$ cat example.txt
UNIX operating system
UNIX and Linux operating system
Linux operation system

Now we want to search all lines in file example.txt which contains word UNIX but same time doesn’t contain world Linux.

$ grep UNIX example.txt
UNIX operating system
UNIX and Linux operating system

Now to exclude all lines which contains Linux we will apply another grep command in this output with option -v to exclude matching word as shown in below grep command :

$ grep UNIX example.txt | grep -v Linux
UNIX operating system

 2 : How to count occurrence of a word in a file using grep command

Below example of command will print how many times word “Error” has appeared in logfile.txt.

$ grep -c "Error" logfile.txt

If we apply this grep command on our example file to find how many lines contains word e.g. UNIX has occurred in the file :

$ grep -c UNIX example.txt
2

 3 : printing lines before and after of matching word using grep

$ grep --context=6 successful logfile.txt

$ grep -C 2 'hello' *

$ egrep 'Error|Exception' logfile.txt

$ grep -i Error logfile

$ zgrep -i Error *.gz

$ grep -w ERROR logfile.txt

$ grep 'ERROR>' *

$ grep -l ERROR *.log

grep -n july filename

$ grep -n ERROR log file.

$ grep -R store *

$ grep Exception today.log --color

Read more

11. Write a command to print the lines that has the the pattern “july” in all the files in a particular directory?

grep july *

This will print all the lines in all files that contain the word “july” along with the file name. If any of the files contain words like “JULY” or “July”, the above command would not print those lines.

12. Write a command to print the lines that has the word “july” in all the files in a directory and also suppress the file name in the output.

grep -h july *

13. When you use a single file as input to the grep command to search for a pattern, it won’t print the filename in the output. Now write a grep command to print the file name in the output without using the ‘-H’ option.

grep pattern file name /dev/null

The /dev/null or null device is special file that discards the data written to it. So, the /dev/null is always an empty file.
Another way to print the file name is using the ‘-H’ option. The grep command for this is

grep -H pattern filename

14. Write a command to print the file names in a directory that does not contain the word “july”?

grep -L july *

The ‘-L’ option makes the grep command to print the file names that do not contain the specified pattern.

15. Write a command to print the lines that starts with the word “start”?

grep '^start' filename

The ‘^’ symbol specifies the grep command to search for the pattern at the start of the line.

16. Running the last executed grep command

This saves a lot of time if you are executing the same command again and again.

!grep

This displays the last executed grep command and also prints the result set of the command on the terminal.

17. Search for a string in a file

This is the basic usage of grep command. It searches for the given string in the specified file.

grep "Error" logfile.txt

This searches for the string “Error” in the log file and prints all the lines that has the word “Error”.

18. Searching for a string in multiple files.

grep "string" file1 file2
grep "string" file_pattern

This is also the basic usage of the grep command. You can manually specify the list of files you want to search or you can specify a file pattern (use regular expressions) to search for.

19. Specifying the search string as a regular expression pattern.

grep "^[0-9].*" file.txt

This will search for the lines which starts with a number.

20. Displaying the lines before the match.

Some times, if you are searching for an error in a log file; it is always good to know the lines around the error lines to know the cause of the error.

grep -B 2 "Error" file.txt

This will prints the matched lines along with the two lines before the matched lines.

21. Displaying the lines after the match.

grep -A 3 "Error" file.txt

This will display the matched lines along with the three lines after the matched lines.

 22. Inverting the pattern match

You can display the lines that are not matched with the specified search sting pattern using the -v option.

grep -v "string" file.txt

23. Displaying the non-empty lines

You can remove the blank lines using the grep command.

grep -v "^$" file.txt

24. Displaying only the matched pattern.

By default, grep displays the entire line which has the matched string. We can make the grep to display only the matched string by using the -o option.

grep -o "string" file.txt

25. Displaying the position of the matched string in the line

The -b option allows the grep command to display the character position of the matched string in a file.

grep -o -b "string" file.txt

26. Matching the lines that start with a string

The ^ regular expression pattern specifies the start of a line. This can be used in grep to match the lines which start with the given string or pattern.

grep "^start" file.txt

27. Matching the lines that end with a string

The $ regular expression pattern specifies the end of a line. This can be used in grep to match the lines which end with the given string or pattern.

grep "end$" file.txt

28.How do you rename the files in a directory with _new as suffix?

ls -lrt|grep '^-'| awk '{print "mv "$9" "$9".new"}' | sh

29. Write command to list all the links from a directory?

ls -lrt | grep "^l"

ls -a | grep '^\.'

ls -l | grep '^-' | awk '{print $5,$9}' |sort -n|awk '{print $2}'

 32.How to find Exception in log files available in current directory and how to find number of occurrence?

$ grep ‘Exception’ log1.txt | wc -l

33.Search for a sample string in particular files ?

– grep .Debug. *.confHere grep uses the string .Debug. to search in all files with extension..conf. under current directory.

grep -v ‘^$’ filename > new_filename

35. How to display the processes that were run by your user name ?

ps -aef | grep <user_name>

36.Delete blank lines in a file ?

– cat sample.txt | grep -v ‘^$’ > new_sample.txt

FIND

37. How to run the last executed find command?

!find

This will execute the last find command. It also displays the last find command executed along with the result on the terminal.

38. How to find for a file using name?

find -name “sum.java”
./bkp/sum.java
./sum.java

This will find all the files with name “sum.java” in the current directory and sub-directories.

39. How to find for files using name and ignoring case?

find –iname “sum.java”
./SUM.java
./bkp/sum.java
./sum.java

This will find all the files with name “sum.java” while ignoring the case in the current directory and sub-directories.

40. How to find for a file in the current directory only?

find -maxdepth 1 -name “sum.java”
./sum.java

This will find for the file “sum.java” in the current directory only

41. How to find for files containing a specific word in its name?

find –name “*java*”
./SUM.java
./bkp/sum.java
./sum.java
./multiply.java

It displayed all the files which have the word “java” in the filename

42. How to find for files in a specific directory?

find /etc -name “*java*”

This will look for the files in the /etc directory with “java” in the filename

43. How to find the files whose name are not “sum.java“?

find –not -name “sum.java”
.
./SUM.java
./bkp
./multiply.java

This is like inverting the match. It prints all the files except the given file “sum.java”.

44. How to limit the file searches to specific directories?

find -name “sum.java”
./tmp/sum.java
./bkp/var/tmp/files/sum.java
./bkp/var/tmp/sum.java
./bkp/var/sum.java
./bkp/sum.java
./sum.java

You can see here the find command displayed all the files with name “sum.java” in the current directory and sub-directories.

a. How to print the files in the current directory and one level down to the current directory?

find -maxdepth 2 -name “sum.java”
./tmp/sum.java
./bkp/sum.java
./sum.java

b. How to print the files in the current directory and two levels down to the current directory?

find -maxdepth 3 -name “sum.java”
./tmp/sum.java
./bkp/var/sum.java
./bkp/sum.java
./sum.java

c. How to print the files in the subdirectories between level 1 and 4?

find -mindepth 2 -maxdepth 5 -name “sum.java”
./tmp/sum.java
./bkp/var/tmp/files/sum.java
./bkp/var/tmp/sum.java
./bkp/var/sum.java
./bkp/sum.java

45. How to find the empty files in a directory?

find . –maxdepth 1 -empty
./empty_file

46. How to find the largest file in the current directory and sub directories

find . -type f -exec ls -s {} \; | sort -n -r | head -1

The find command “find . -type f -exec ls -s {} \;” will list all the files along with the size of the file. Then the sort command will sort the files based on the size. The head command will pick only the first line from the output of sort.

47. How to find the smallest file in the current directory and sub directories

find . -type f -exec ls -s {} \; | sort -n -r | tail -1

Another method using find is

find . -type f -exec ls -s {} \; | sort -n | head -1

48. How to find files based on the file type?

a. Finding socket files

find . -type s

b. Finding directories

find . -type d

c. Finding hidden directories

find -type d -name “.*”

d. Finding regular files

find . -type f

e. Finding hidden files

find . -type f -name “.*”

49. How to find files based on the size?

a. Finding files whose size is exactly 10M

find . -size 10M

b. Finding files larger than 10M size

find . -size +10M

c. Finding files smaller than 10M size

find . –size -10M

50. How to find the files which are modified after the modification of a give file.

find –newer “sum.java”

This will display all the files which are modified after the file “sum.java”

51. Display the files which are accessed after the modification of a give file.

find –anewer “sum.java”

52. Display the files which are changed after the modification of a give file.

find –cnewer “sum.java”

53. How to find the files based on the file permissions?

find . -perm 777

This will display the files which have read, write, and execute permissions. To know the permissions of files and directories use the command “ls -l”.

find –perm option is used to find files based upon permissions.

You can used find –perm 444 to get all files which allows read to owner, group and others.

javin@testenv1:~/java $ find . -perm 644
./.vimrc
./OnlineStockTrading.java

find out all the executable files, you can also modify it to find all the read only files or files having write permission etc by changing permissions e.g. to find all read only files in current directory :

find . –perm 555  Here “.” or period denotes current directory. You can replace it with any directory you want.

54. Write a command to list the files that are accessed 5 days ago in the current directory?
find -atime 5 -type f

55. Write a command to list the files whose status is changed 5 days ago in the current directory?
find -ctime 5 -type f

56. Write a command to list the files that were modified 5 days ago in the current directory?
find –mtime 5 -type f

57.How to find files which has been modified less than one day, minute or hour  in Unix:

find –mtime is used to search files based upon modification time.

find –atime which denote last accessed time of file

find –ctime denotes last changed time. + sign is used to search for greater than, – sign is used to search for less than and without sign is used for exact.

For example find –mtime -1 will search all files which has been modified

javin@testenv1 ~/java : find . -mtime 1  (find all the files modified exact 1 day)

javin@testenv1 ~/java : find . -mtime -1 (find all the files modified less than 1 day)
.
./StockTrading.java

javin@testenv1 ~/java : find . -mtime +1 (find all the files modified more than 1 day)
./.vimrc
./OnlineStockTrading.java
./StockTrading.java~

58. Find the files which are modified within 30 minutes.

find . -mmin -30

59. Find the files which are modified within 1 day.

find . -mtime -1

60. How to find the files which are modified 30 minutes back

find . -not -mmin -30

61. How to find the files which are modified 1 day back.

find . -not -mtime -1

62.Print the files which are accessed within 1 hour.

find . -amin -60

63. Print the files which are accessed within 1 day.

find . -atime -1

64. Display the files which are changed within 2 hours.

find . -cmin -120

65. Display the files which are changed within 2 days.

find . -ctime -2

66. How to find the files which are created between two files.

find . -cnewer f1 -and ! -cnewer f2

67. How to find the permissions of the files which contain the name “java“?

find -name “*java*”|xargs ls -l

Alternate method is

find -name “*java*” -exec ls -l {} \;

68. Find the files which have the name “java” in it and then display only the files which have “class” word in them?

find -name “*java*” -exec grep -H class {} \;

69. How to remove files which contain the name “java”.

find -name “*java*” -exec rm -r {} \;

70. Write a command to search for the file ‘test’ in the current directory?
find -name test -type f

71. Write a command to search for the file ‘temp’ in ‘/usr’ directory?
find /usr -name temp -type f

72. Write a command to search for the files in the current directory which are not owned by any user in the /etc/passwd file?
find . -nouser -type f

73. Write a command to search for the files in ‘/usr’ directory that start with ‘te’?
find /usr -name ‘te*’ -type f

74. Write a command to search for the files that start with ‘te’ in the current directory and then display the contents of the file?
find . –name ‘te*’ -type f -exec cat {} \;

75. Write a command to list the files in ‘/usr’ directory that start with ‘ch’ and then display the number of lines in each file?
find /usr -name ‘ch*’ -type f -exec wc -l {} \;

76.How to delete temporary files using find command in Unix?

In order to delete files you can use either –delete option of find command or use xargs in combination. Its better to create house keeping script for such task which can perform cleanup on periodic basis.

find . -name “*.tmp” -print | xargs rm –f

considering use of -print0 to avoid problems with white space in the path when piping to xargs (use with the xargs -0 option)

77.How to find all text file which contains word Exception using find command in Unix ?

find . –name “*.java” –print | xargs grep “MemoryCache”,

this will search all java files starting from current directory for word “MemoryCache”.

we can also leave -print option in all cases because its default for UNIX find command You can further sort result of find command using Sort command in unix.

find . –name “*.txt” –print | xargs grep “Exception”

78. Write a command to search for zero byte size files in the current directory?
find –size 0 -type f

79. Finding files only in current directory not searching on sub directories:

–type option can be used to specifiy search for only file, link or directory and maxdepth specifies how deep find has to search.

find . -maxdepth 1 -type f -newer first_file

Another way of doing it is below:

find . -type f -cmin 15 -prune
Means type file, last modified 15 minutes ago, only look at the current directory. (No sub-directories)

80 .How to find files based on size in Unix and Linux

find . -size +1000c -exec ls -l {} \;

find . -size +10000c -size -50000c -print
This find example lists all files that are greater than 10,000 bytes, but less than 50,000 bytes:

81.How to find files some days older and above certain size

find command will find which are more than 10 days old and size greater than 50K.

find . -mtime +10 -size +50000c -exec ls -l {} \;

You can use “awk“ in combination of find to print a formatted output e.g. next command will find all of the symbolic links in your home directory, and print the files your symbolic links points to:

find . –type l -print | xargs ls -ld | awk ‘{print $10}’

“.” says starts from current directory and include all sub directory and  “-type l” says list all links.
Tip: 
$* :    $* is one of the special bash parameter which is used to expands positional parameters from position one.

82.How to use find command on file names with space in

find -print0 and xargs -0 on find examples,

we don’t specify any expression after find command the default option is -print which prints the name of each found files followed by \n or newline.since we mostly pipe output of find command to xargs -print could cause problem if file name itself contain new line or any form of white space.

To resolve this issue instead of -print use -print0.

Difference between find -print and find -print0 is, print0 display file name on the stdout followed by a “NUL” character and then you can use xargs -0command to process file names with null character.

UNIX find command example with file name having space in them:

javin@testenv1:~/test find . -name “*equity*” -print
./cash equity trading ./equity~
You see here “cash equity trading” has space in there name

javin@testenv1:~/test find . -name “*equity*” -print | xargs ls -l
ls: cannot access ./cash: No such file or directory
ls: cannot access equity: No such file or directory
ls: cannot access trading: No such file or directory
-r–r–r– 1 stock_trading cash_domain trading 0 Jul 15 11:42 ./equity~
Now if we pass this to xargs, xargs treat them as three separate files.

javin@testenv1:~/test find . -name “*equity*” -print0 | xargs ls

xargs: WARNING: a NUL character occurred in the input.  It cannot be passed through in the argument list.  Did you mean to use the –null option?

ls: cannot access ./cash: No such file or directory
ls: cannot access equity: No such file or directory
ls: cannot access trading: No such file or directory
Now to solve this we have used find command with -print0 which appends NUL character on file name but without xargs -0, xargs will not able to handle those inputs.

javin@testenv1:~/test find . -name “*equity*” -print0 | xargs -0 ls -l
-rw-r–r– 1 stock_trading cash_domain trading 0 Jul 21 09:54 ./cash equity trading
-r–r–r– 1 stock_trading cash_domain trading 0 Jul 15 11:42 ./equity~

you can see with find -print0| xargs -0 it looks good

In conclusion always use find -print0 along with xargs -0 if you see slightest possibilities of file names containing space in UNIX or Linux.

• find –print and find is same as –print is a default option of find command.
• find –print0 should be used to avoid any issue with white space in file name or path while forwarding output to xargs, also use xargs -0 along with find –print0.
• find has an option called –delete which can be used in place of  -exec rm {} \;

83.find all files in current and subdirectories which contains ‘log’ name?

$ find . -name ‘log’

84.Write a command to find all of the files which have been accessed within the last 30 days.

find / -type f -atime -30 > December.files

This command will find all the files under root, which is ‘/’, with file type is file. ‘-atime -30′ will give all the files accessed less than 30 days ago. And the output will put into a file call December.files.

. Write a command to search for the file ‘map’ in the current directory?

find -name map -type f

85. Write a command to list the files in ‘/usr’ directory that start with ‘ch’ and then display the number of lines in each file?

wc -l /usr/ch*

find /usr -name 'ch*' -type f -exec wc -l {} \;

find . -depth -print

find -size 0 -type f

CUT

> cat file.txt
unix or linux os
is unix good os
is linux good os

cut -c4 file.txt
x
u
l

cut -c4,6 file.txt
xo
ui
ln

cut -c4-7 file.txt
x or
unix
linu

cut -c-6 file.txt
unix o
is uni
is lin

cut -c10- file.txt
inux os
ood os
good os

cut -c- file.txt

cut -d' ' -f2 file.txt
or
unix
linux

cut -d' ' -f2,3 file.txt
or linux
unix good
linux good

cut -d' ' -f1-3 file.txt

cut -d' ' -f-3 file.txt

cut -d' ' -f2- file.txt

cut -d':' -f1 /etc/passwd

> cat filenames.txt
logfile.dat
sum.pl
add_int.sh

rev filenames.txt | cut -d'.' -f1

cat /dev/null >  filename

cut –f<n> -d' '

SORT

The options are:

-b : Ignores leading spaces in each line
-d : Uses dictionary sort order. Conisders only spaces and alphanumeric characters in sorting
-f : Uses case insensitive sorting.
-M : Sorts based on months. Considers only first 3 letters as month. Eg: JAN, FEB
-n : Uses numeric sorting
-R : Sorts the input file randomly.
-r : Reverse order sorting
-k : Sorts file based on the data in the specified field positions.
-u : Suppresses duplicate lines
-t : input field separator

Sort Command Examples:

Before practicing the examples create the below two files in your unix system:

> cat order.txt
Unix distributed 05 server
Linux virtual 3 server
Unix distributed 05 server
Distributed processing 6 system

> cat delim_sort.txt
Mayday|4
Janmon|1
Declast|12

106. Sorting lines of text

The default sort command uses alphabetical order (ASCII order) to sort the file. It treats each line as a string and then sorts the lines.

> sort order.txt
Distributed processing 6 system
Linux virtual 3 server
Unix distributed 05 server
Unix distributed 05 server

107. Sorting based on the field positions.

You can specify the field postions using the -k option of sort command. The sort command uses the space or tab as the default delimiter. To sort based on the data in the second field, run the below command:

> sort -k2 order.txt
Unix distributed 05 server
Unix distributed 05 server
Distributed processing 6 system
Linux virtual 3 server

You can also pecify more than field with k option as a comma separated list. The below command uses the second and fourth fields to sort the data.

> sort -k2,4 order.txt

108. Numeric sorting

Instead of the default alphabetical sorting order, you can make the sort command to sort in numeric order using the -n option. This is shown below:

> sort -nk3 order.txt
Linux virtual 3 server
Unix distributed 05 server
Unix distributed 05 server
Distributed processing 6 system

109. Sort in reverse order

By default, the sort command sorts the data in ascending order. You can change this to descending order using the -r option.

> sort -nrk3 order.txt
Distributed processing 6 system
Unix distributed 05 server
Unix distributed 05 server
Linux virtual 3 server

110. Suppressing duplicates or Print only unique values

You can produce only unique values in the output using the – u option of the sort command.

> sort -u order.txt
Distributed processing 6 system
Linux virtual 3 server
Unix distributed 05 server

Another way is piping the output of sort command to uniq command.

> sort order.txt | uniq

111. Delimited file input

In the second, third and fourth examples we have sorted the data based on the field positions. Here the fields are separted by space or tab character. What if the fields are specifed by any other character? In such cases, we have to specify the input delimiter with the -t option. An example is shown below:

> sort -t'|' -nrk2 delim_sort.txt
Declast|12
Mayday|4
Janmon|1

112. Sorting on months.

We can sort the data in the monthwise using the -M option of the sort command. This is shown below:

> sort -M delim_sort.txt
Janmon|1
Mayday|4
Declast|12

ps-ef

TAR

c : creates a tar file.
v : verbose. Displays the files information.
f : Specify the tar file name.
r : updates the tar file with new files.
x : Extracts files from the archive (tar file).
t : view contents of tar file.
z : Specify the tar command to create a tar file using gzip in unix.
j : uses bzip2 to create the tar file.

> ls -l 
drwxr-xr-x 2 user group 4096 Aug  8 03:23 debian
-rw-r--r-- 1 user group  174 Aug  2 23:39 file
-rw-r--r-- 1 user group    0 Aug  8 03:22 linux_server.bat
-rw-r--r-- 1 user group   76 Aug  2 02:21 test.sh
-rw-r--r-- 1 user group    0 Aug  8 03:22 unix_distro

> tar -cvf archive.tar *
debian/
file
linux_server.bat
test.sh
unix_distro

> ls
archive.tar  debian  file  linux_server.bat  test.sh  unix_distro

> tar -tvf archive.tar
drwxr-xr-x user/group   0 2012-08-08 03:23:07 debian/
-rw-r--r-- user/group 174 2012-08-02 23:39:51 file
-rw-r--r-- user/group   0 2012-08-08 03:22:19 linux_server.bat
-rw-r--r-- user/group  76 2012-08-02 02:21:32 test.sh
-rw-r--r-- user/group   0 2012-08-08 03:22:09 unix_distro

>touch red-hat-linux.dat

>tar -rvf archive.tar red-hat-linux.dat
red-hat-linux.dat

>tar -tvf archive.tar
drwxr-xr-x pcenter/pcenter   0 2012-08-08 03:23:07 debian/
-rw-r--r-- pcenter/pcenter 174 2012-08-02 23:39:51 file
-rw-r--r-- pcenter/pcenter   0 2012-08-08 03:22:19 linux_server.bat
-rw-r--r-- pcenter/pcenter  76 2012-08-02 02:21:32 test.sh
-rw-r--r-- pcenter/pcenter   0 2012-08-08 03:22:09 unix_distro
-rw-r--r-- pcenter/pcenter   0 2012-08-08 04:00:00 red-hat-linux.dat

> tar -xvf archive.tar
debian/
file
linux_server.bat
test.sh
unix_distro

Compressing files using gzip

> tar -zcvf new_tar_file.tar.gz *

Compressing files using bzip2

> tar -jcvf new_tar_file.tar.bz2 *

To view files in a gzip compressed tar file
> tar -ztvf new_tar_file.tar.gz

To extract files from a gip compressed tar file
> tar -zxvf new_tar_file.tar.gz

To view files in a bzip2 compressed tar file
> tar -jtvf new_tar_file.tar.bz2

To extract files from a bzip2 compressed tar file
> tar -jxvf new_tar_file.tar.bz2

> tar -cvf unix_files.tar unix_server.bat unix_system.dat

To extract a specifi file

> tar -xvf unix_files.tar unix_server.bat

To extract all files that start with name unix

> tar -xvf unix_files.tar --wildcards "unix*"

> tar -xv -Mf archive.tar -Mf unix_files.tar

you see creating tar file with gzip is very easy just use “-z” option and it will crate a gzip tar.tgz or tar.gz extension

121.Calculating size of tar file in UNIX

Some time its useful to know the size of tar file before creating it and you can get it by using unix tar command as shown in below example:

stock_trader@system:~/test tar -cf – * | wc -c

20480

Size shown here is in KB and you can also calculate size for compressed tar file by using “z” for gzip and “j” for bzip2

> ls -a
.  ..  documents  .hidden_file  sum.pl

> ls -A
documents  .hidden_file  sum.pl

> ls -F
documents/  sum.pl link@

> ls -1
documents
sum.pl

> ls -i1
10584066 documents
3482450 sum.pl

> ls -l
total 16
drwxr-xr-x 2 matt db 4096 Jan 30 23:08 documents
-rw-r--r-- 1 matt db   49 Jan 31 01:17 sum.pl

> ls -t1
sum.pl
documents

> ls -rt1
documents
sum.pl

> ls -R
.:
documents  sum.pl

./documents:
file.txt

> ls /usr/local/bin

> ls -x

ls -l | grep '^-' | awk '/^-/ {if ($5 !=0 ) print $9 }'

ls -l | grep '^-'| awk 'BEGIN {sum=0} {sum = sum + $5} END {print sum}'

ls -l | grep '^-' |sort -nr -k 5

ls -l|grep '^-'|wc -l

cp sum.pl tmp/

> cp sum.pl tmp/
cp: overwrite `tmp/sum.pl'?

cp log.dat bad.dat tmp/

cp *.dat tmp/

cp /usr/local/bin/multiply.sh .

cp docs/* tmp/

cp docs/* scripts/* tmp/

cp -r docs tmp/

cp -f force_file.txt /var/tmp/

cd [directory]
Here directory is the name of the directory where you wish to go.

> pwd
/usr/local/bin

> cd
> pwd
/home/matt

> pwd
/var/tmp
> cd ..
> pwd
/var

> pwd
/usr/local/bin
> cd ../../
> pwd
/usr

> cd /usr/bin

> pwd
/var/tmp
> cd ../lib
> pwd
/var/lib

> pwd
/home/matt/documents
> cd /home/matt/backup
>pwd
/home/matt/backup
> cd -
> pwd
/home/matt/documents

rmdir docs/
rmdir: docs/: Directory not empty

rm doc/*
rmdir docs/

rmdir -p docs/entertainment/movies/

rm doc*

rm [options] [directory|file]

f : Removes all files in a directory without prompting the user.
i : Interactive: prompts the user for confirmation before deleting a file.
R or r : Recursively remove directories and sub directories.

rm logfile.dat

rm *

rm docs/

rm -r docs

mv [options] oldname newname

f : Do not prompt before overwriting a file. 
i : Prompts for the user input before overwriting a file.

> mv log.dat bad.dat

mv -i log.dat bad.dat
mv: overwrite `bad.dat'?

mv docs/ documents/

mv sum.pl /var/tmp/

mv documents /tmp/

mv * /var/tmp/

uniq [option] filename

> cat example.txt
Unix operating system
unix operating system
unix dedicated server
linux dedicated server

> uniq example.txt
unix operating system
unix dedicated server
linux dedicated server

> sort example.txt | uniq

> uniq -c example.txt
      2 unix operating system
      1 unix dedicated server
      1 linux dedicated server

> uniq -d example.txt
unix operating system

> uniq -D example.txt
unix operating system
unix operating system

> uniq -f2 example.txt
unix operating system
unix dedicated server

> uniq -u example.txt
unix dedicated server
linux dedicated server

ls *.log
oracle.log  storage.log

> ls *.log | xargs -i mv {} {}_bkp
> ls *_bkp
oracle.log_bkp  storage.log_bkp

find . -name "*.bash"
./sql_server.bash
./mysql_backup.bash
./oracle_backup.bash

find . -name "*.bash" |xargs grep "echo"

ls "*.tmp" | xargs rm

ls -1
oracle.txt
online_backup.dat
mysql_storage.bat

ls -1 | xargs
oracle.txt online_backup.dat mysql_storage.bat

Creating a file which contains space in the name
> touch "oracle storage"

> ls oracle\ storage | xargs grep "log"
grep: oracle: No such file or directory
grep: storage: No such file or directory

> ls oracle\ storage | xargs -i grep "log" {}

> ls -1
backup
mysql
network
online
oracle
storage
wireless

> ls -1 | xargs -n 3 echo
backup mysql network
online oracle storage
wireless

find . -print0 | xargs -0 rm

awk 'BEGIN {start_action} {action} END {stop_action}' filename

-rw-r--r-- 1 center center  0 Dec  8 21:39 p1
-rw-r--r-- 1 center center 17 Dec  8 21:15 t1
-rw-r--r-- 1 center center 26 Dec  8 21:38 t2
-rw-r--r-- 1 center center 25 Dec  8 21:38 t3
-rw-r--r-- 1 center center 43 Dec  8 21:39 t4
-rw-r--r-- 1 center center 48 Dec  8 21:39 t5

-rw-r--r--
-rw-r--r--
-rw-r--r--
-rw-r--r--
-rw-r--r--
-rw-r--r--

#!/usr/bin/awk -f
BEGIN {sum=0} 
{sum=sum+$5} 
END {print sum}

-rw-r--r-- 1 pcenter pcenter 43 Dec  8 21:39 t4

square of 1 is 1
square of 2 is 4
square of 3 is 9
square of 4 is 16
square of 5 is 25

39 p1
15 t1
38 t2
38 t3
39 t4
39 t5

center 0
center 17
center 26
center 25
center 43
center 48

center:0
center:17
center:26
center:25
center:43
center:48

1 U,N,UNIX,000
2 N,P,SHELL,111
3 I,M,UNIX,222
4 X,Y,BASH,333
5 P,R,SCRIPT,444

1 U,N,UNIX,000
3 I,M,UNIX,222

awk '{ 
        split($2,arr,","); 
        if(arr[3] == "UNIX") 
        print $0 
} ' file.txt

1 A
2 B
3 C
4 D
5 E
6 F

1 A
2 B
9 Z
3 C
4 D
9 Z
5 E
6 F
9 Z

awk '{ 
 if(NR%2 == 0) 
 {
  print $0"\n9 Z";
 } 
 else 
 {
  print $0
 }
     }' file.txt

AAA 1
BBB 2
CCC 3
AAA 4
AAA 5
BBB 6
CCC 7
AAA 8
BBB 9
AAA 0

AAA 1
BBB 2
CCC 3
AAA 4
AAA 5
BBB 6
CCC 7
ZZZ 8
BBB 9
AAA 0

awk 'BEGIN {count=0} 
 { 
  if($1 == "AAA") 
  { 
   count++
  } 
  if(count == 4) 
  { 
   sub("AAA","ZZZ",$1) 
  } 
 } 
 {
  print $0
 }' file.txt

A 10
B 39
C 22
D 44
E 75
F 89
G 67

174, 172

awk '{ 
 if(NR%2 == 1) 
 {
  sum_e = sum_e + $2
 } 
 else 
 {
  sum_o = sum_o + $2
 }
      } 
      END { print sum_e,sum_o }' file.txt

awk ' BEGIN{ 
 for(i=0;i<=10;i++) 
 { 
  if (i <=1 )
  {
   x=0;
   y=1;
   print i;
  }
  else
  {
   z=x+y;
   print z; 
   x=y;
   y=z;
  }
 } 
    }'

0
1
1
2
3
5
8
13
21
34
55

0012345
05678
01010
00001

12345
5678
1010
1

awk '{print $1 + 0}' file.txt
awk '{printf "%d\n",$0}' file.txt

awk 'BEGIN { for(i=1;i<=10;i++) {print "square of",i,"is",i*i;}}'

awk -f filename

awk '{ if( $0 ~ /:/ ) { FS=":"; } else { FS =" "; } print $3 }' filename

awk '{print NR, $0}' filename

awk 'BEGIN {RS="";FS="\n"} {print $2,$3}' filename

wc -l filename

awk 'BEGIN {sum=0} {sum=sum+1} END {print sum}' filename
awk 'END{print NR}' filename

awk 'BEGIN {ORS=""} { for(i=NF;i>0;i--) print $i," "; print "\n"}' filename

echo apple | awk '{print toupper(substr($1,1,1)) tolower(substr($1,2))}'

SED

>cat file.txt
unix is great os. unix is opensource. unix is free os.
learn operating system.
unixlinux which one you choose.

>sed 's/unix/linux/' file.txt
linux is great os. unix is opensource. unix is free os.
learn operating system.
linuxlinux which one you choose.

>sed 's/unix/linux/2' file.txt
unix is great os. linux is opensource. unix is free os.
learn operating system.
unixlinux which one you choose.

>sed 's/unix/linux/g' file.txt
linux is great os. linux is opensource. linux is free os.
learn operating system.
linuxlinux which one you choose.

>sed 's/unix/linux/3g' file.txt
unix is great os. unix is opensource. linux is free os.
learn operating system.
unixlinux which one you choose.

>sed 's/http:\/\//www/' file.txt

>sed 's_http://_www_' file.txt
>sed 's|http://|www|' file.txt

>sed 's/unix/{&}/' file.txt
{unix} is great os. unix is opensource. unix is free os.
learn operating system.
{unix}linux which one you choose.

>sed 's/unix/{&&}/' file.txt
{unixunix} is great os. unix is opensource. unix is free os.
learn operating system.
{unixunix}linux which one you choose.

>sed 's/\(unix\)/\1\1/' file.txt
unixunix is great os. unix is opensource. unix is free os.
learn operating system.
unixunixlinux which one you choose.

>sed 's/\(unix\)\(linux\)/\2\1/' file.txt
unix is great os. unix is opensource. unix is free os.
learn operating system.
linuxunix which one you choose.

>sed 's/^\(.\)\(.\)\(.\)/\3\2\1/' file.txt
inux is great os. unix is opensource. unix is free os.
aelrn operating system.
inuxlinux which one you choose.

>sed 's/unix/linux/p' file.txt
linux is great os. unix is opensource. unix is free os.
linux is great os. unix is opensource. unix is free os.
learn operating system.
linuxlinux which one you choose.
linuxlinux which one you choose.

>sed -n 's/unix/linux/p' file.txt
linux is great os. unix is opensource. unix is free os.
linuxlinux which one you choose.

>sed 's/unix/linux/' file.txt| sed 's/os/system/'
linux is great system. unix is opensource. unix is free os.
learn operating system.
linuxlinux which one you chosysteme.

>sed -e 's/unix/linux/' -e 's/os/system/' file.txt
linux is great system. unix is opensource. unix is free os.
learn operating system.
linuxlinux which one you chosysteme.

>sed '3 s/unix/linux/' file.txt
unix is great os. unix is opensource. unix is free os.
learn operating system.
linuxlinux which one you choose.

>sed '1,3 s/unix/linux/' file.txt
linux is great os. unix is opensource. unix is free os.
learn operating system.
linuxlinux which one you choose.

>sed '2,$ s/unix/linux/' file.txt
linux is great os. unix is opensource. unix is free os.
learn operating system.
linuxlinux which one you choose.

>sed '/linux/ s/unix/centos/' file.txt
unix is great os. unix is opensource. unix is free os.
learn operating system.
centoslinux which one you choose.

>sed '2 d' file.txt
>sed '5,$ d' file.txt

>sed 'p' file.txt

>grep 'unix' file.txt
>sed -n '/unix/ p' file.txt

>grep -v 'unix' file.txt
>sed -n '/unix/ !p' file.txt

>sed '/unix/ a "Add a new line"' file.txt
unix is great os. unix is opensource. unix is free os.
"Add a new line"
learn operating system.
unixlinux which one you choose.
"Add a new line"

>sed '/unix/ i "Add a new line"' file.txt
"Add a new line"
unix is great os. unix is opensource. unix is free os.
learn operating system.
"Add a new line"
unixlinux which one you choose.

>sed '/unix/ c "Change line"' file.txt
"Change line"
learn operating system.
"Change line"

>sed 'y/ul/UL/' file.txt
Unix is great os. Unix is opensoUrce. Unix is free os.
Learn operating system.
UnixLinUx which one yoU choose.

Sed Command to Delete Lines: Sed command can be used to delete or remove specific lines which matches a given pattern or in a particular position in a file. Here we will see how to delete lines using sed command with various examples.

> cat file
linux
unix
fedora
debian
ubuntu

> sed 'Nd' file

> sed '1d' file
unix
fedora
debian
ubuntu

> sed '$d' file
linux
unix
fedora
debian

> sed '2d' file
linux
fedora
debian
ubuntu

> sed 'm,nd' file

> sed '2,4d' file
linux
ubuntu

> sed '1!d' file
linux

> sed '$!d' file
ubuntu

> sed '2,4!d' file
unix
fedora
debian

> sed '1d;$d' file
unix
fedora
debian

> sed '/^$/d' file

> sed '/^u/d' file
linux
fedora
debian

> sed '/x$/d' file
fedora
debian
ubuntu

> sed '/^[A-Z]*$/d' file

> sed '/debian/d' file
linux
unix
fedora
ubuntu

> sed '/fedora/,$d' file
linux
unix

> sed '${/ubuntu/d;}' file
linux
unix
fedora
debian

> sed -i '1d' file

sed '1d' file > newfile

 SED

How to remove the first 10 lines from a file?

sed '1,10 d' < filename

318. Write a command to duplicate each line in a file?

sed 'p' < filename

327. How to replace the word “Gun” with “Pen” in the first 100 lines of a file?

sed '1,00 s/Gun/Pen/' < filename

334. How to replace the second occurrence of the word “bat” with “ball” in a file?

sed 's/bat/ball/2' < filename

335. How to remove all the occurrences of the word “jhon” except the first one in a line with in the entire file?

sed 's/jhon//2g' < filename

336. How to replace the word “lite” with “light” from 100th line to last line in a file?

sed '100,$ s/lite/light/' < filename

348. Write a command to replace the word “bad” with “good” in file?

sed s/bad/good/ < filename

349. Write a command to replace the word “bad” with “good” globally in a file?

sed s/bad/good/g < filename

350. Write a command to replace the word “apple” with “(apple)” in a file?

sed s/apple/(&)/ < filename

351. Write a command to switch the two consecutive words “apple” and “mango” in a file?

sed 's/\(apple\) \(mango\)/\2 \1/' < filename

280. How to remove the header from a file?

sed -i '1 d' filename

281. How to remove the footer from a file?

sed -i '$ d' filename

282. Write a command to find the length of a line in a file?

The below command can be used to get a line from a file.

sed –n '<n> p' filename

We will see how to find the length of 10th line in a file

sed -n '10 p' filename|wc -c

292. How to display the first 20 lines of a file? By default, the head command displays the first 10 lines from a file. If we change the option of head, then we can display as many lines as we want.

head -20 filename

An alternative solution is using the sed command

sed '21,$ d' filename

The d option here deletes the lines from 21 to the end of the file

293. Write a command to print the last line of a file?

The tail command can be used to display the last lines from a file.

tail -1 filename

Alternative solutions are:

sed -n '$ p' filename
awk 'END{print $0}' filename

286. How to replace the n-th line in a file with a new line in Unix?

sed -i'' '10 d' filename      # d stands for delete
sed -i'' '10 i new inserted line' filename    # i stands for insert

301. How do you remove the first number on 10th line in file?

sed '10 s/[0-9][0-9]*//' < filename

307. Write a command to remove the first number on all lines that start with “@”?

sed '\,^@, s/[0-9][0-9]*//' < filename

312. How to duplicate empty lines in a file?

sed '/^$/ p' < filename

 

340. How to replace the character ‘/’ with ‘,’ in a file?

sed 's/\//,/' < filename
sed 's|/|,|' < filename

 

.Display the last newly appending lines of a file during appendingdata to the same file by some processes ?

– tail .f Debug.logHere tail shows the newly appended data into Debug.log by some processes/user.

Explain iostat, vmstat and netstat?

• • Iostat: reports on terminal, disk and tape I/O activity.
• Vmstat: reports on virtual memory statistics for processes, disk, tape and CPU activity.
• Netstat: reports on the contents of network data structures.

. How to find out the usage of the CPU by the processes?

The top utility can be used to display the CPU usage by the proce

. Write a command to remove the prefix of the string ending with ‘/’.

The basename utility deletes any prefix ending in /. The usage is mentioned below:

basename /usr/local/bin/file

This will display only file

.Display the Disk Usage of file sizes under each directory in currentDirectory ?

– du -k * | sort .nr (or) du .k . | sort -nr

.Change to a directory, which is having very long name ?

– cd CDMA_3X_GEN*Here original directory name is . .CDMA_3X_GENERATION_DATA..

.Set the Display automatically for the current new user ?

– export DISPLAY=`eval ‘who am i | cut -d”(” -f2 | cut -d”)” -f1′`Here in above command, see single quote, double quote, grave ascent is used. Observe carefully.

.Display the processes, which are running under yourusername ?

– ps .aef | grep MaheshvjHere, Maheshvj is the username.

.List some Hot Keys for bash shell ?

– Ctrl+l . Clears the Screen. Ctrl+r . Does a search in previously given commands in shell. Ctrl+u – Clears the typing before the hotkey. Ctrl+a . Places cursor at the beginning of the command at shell. Ctrl+e . Places cursor at the end of the command at shell. Ctrl+d . Kills the shell. Ctrl+z . Places the currently running process into background.

.How to save man pages to a file ?

– man <command> | col .b > <output-file>Example : man top | col .b > top_help.txt

.How to know the date & time for . when script is executed ?

– Add the following script line in shell script.eval echo “Script is executed at `date`” >> timeinfo.infHere, .timeinfo.inf. contains date & time details ie., when script is executed and history related to execution.

.How do you find out drive statistics ?

– iostat -E

.Display disk usage in Kilobytes ?

– du -k

.Display top ten largest files/directories

 – du -sk * | sort -nr | head

.How much space is used for users in kilobytes ?

– quot -af

.How to create null file ?

– cat /dev/null > filename1

.Access common commands quicker ?

– ps -ef | grep -i $@

Display the page size of memory ?

– pagesize -a

.Display Ethernet Address arp table ?

– arp -a

.Display the no.of active established connections to localhost ?

– netstat -a | grep EST

259.Display the state of interfaces used for TCP/IP traffice ?

– netstat -i

.Display the parent/child tree of a process ?

– ptree <pid> Example: ptree 1267

.Show the working directory of a process ?

– pwdx <pid> Example: pwdx 1267

.Display the processes current open files ?

– pfiles <pid> Example: pfiles 1267

.Display the inter-process communication facility status ?

– ipcs

.Display the top most process utilizing most CPU ?

– top .b 1

.Alternative for top command ?

– prstat -a

.What is the most graceful way to get to run level single user mode?

A: The most graceful way is to use the command init s.
If you want to shut everything down before going to single user mode then do init 0 first and from the ok prompt do a boot -s.

 .How to find current running processes in unix server?

$ ps -ef

and if we want to find specific process we can use ‘grep’ with pipe
$ ps -ef | grep -i ‘application’

 .How to find process which is taking maximum memory in server?
$ top
top command tell us about cpu usage , process id and other details. below is output of top command

 

.How do you access command line arguments from within a shell script?

Arguments passed from the command line to a shell script can be accessed within the shell script by using a $ (dollar sign) immediately followed with the argument’s numeric position on the command line.

 .How to tails last 200 lines of any log fine?

$ tail -200f filename.txt

 .How to find remaining disk space in unix\linux server?

$ df -kl

df -kl

Filesystem   1024-blocks      Used Available Capacity  iused    ifree %iused  Mounted on

/dev/disk0s2   244277768 153679844  90341924    63% 38483959 22585481   63%   /

 .How to make any script file executable?

    $chmod 755 *.sh

. How to kill process in unix server?
$ kill -9 #pid
these #pid can be found using ps -ef command.

 

. How to display the 10th line of a file?

head -10 filename | tail -1

. How to reverse a string in unix?

echo "java" | rev

. How to get the last word from a line in Unix file?

echo "unix is good" | rev | cut -f1 -d' ' | rev

. How to check if the last command was successful in Unix?

echo $?

. How will you find which operating system your system is running on in UNIX?

uname -a

. Create a read-only file in your home directory?

touch file; chmod 400 file

. How do you see command line history in UNIX?

The ‘history’ command can be used to get the list of commands that we are executed.

. Write a command to convert a string from lower case to upper case?

echo "apple" | tr [a-z] [A-Z]

. Write a command to redirect the output of date command to multiple files?

The tee command writes the output to multiple files and also displays the output on the terminal.

date | tee -a file1 file2 file3

. How to create an alias for the complex command and remove the alias?

The alias utility is used to create the alias for a command. The below command creates alias for ps -aef command.

alias pg='ps -aef'

If you use pg, it will work the same way as ps -aef.

To remove the alias simply use the unalias command as

unalias pg

. Write a command to display today’s date in the format of ‘yyyy-mm-dd’?

The date command can be used to display today’s date with time

date '+%Y-%m-%d'

. List out some of the Hot Keys available in bash shell?

• Ctrl+l – Clears the Screen.
• Ctrl+r – Does a search in previously given commands in shell.
• Ctrl+u – Clears the typing before the hotkey.
• Ctrl+a – Places cursor at the beginning of the command at shell.
• Ctrl+e – Places cursor at the end of the command at shell.
• Ctrl+d – Kills the shell.
• Ctrl+z – Places the currently running process into background.

. What is the difference between join -v and join -a?

join -v : outputs only matched lines between two files. join -a : In addition to the matched lines, this will output unmatched lines also.

cal 03 1985

cat file1 file2 file3 > file

yes <your_name> | head -100