How To Use grep Command In Linux / UNIX

This Tutorial is so far helpful to me.

Thank you..!!

Very helpful. saved my time.

what if i want to search like this

avoid using * grep -i “spq” tt.sh
then you will get all the words which will have spq.
if some thing need to refrained from that need to get the desired out put then use

grep -i “spq” tt.sh | grep -v ” somepattern”

This helps a lot,,

How can i do calculation on dates;
eg to know the number of days between ‘todays date’ and a day like ‘15/may/2009′

please help

Hi,
How can I use grep function to search files that file name with “ord” or “rec” from specific dir??

Hi,
No one know how to use grep function to search files that file name with “ord” or “rec” from specific dir??

Hi,
I’d like to get the total cpu and memory usage easily and I think of using ‘dstat’ command. Can I get the values corresponding to the free and used column with grep?

------memory-usage-----
used buff cach free
153M 876k 24M 4392k

cheers!

For those who want to search files with wild cards and the like, try the find command with -exec. find /dir/to/search/ -iname *.cpp -exec grep 'word' '{}' \;
and snake, I do not think it is possible to search columns with grep, I’m 98% sure that it is line (row) only.

whats the use of egrep and fgrep
give examples of both

this is the best and the most understandable tutorial i have seen till date.
GOOD WORK!!

hi this is really really helpful and very fast introduction for grep very nice

clean and accurate .thanks

hi all..
can anyone please explain me about this command
ps -ef|grep -v grep|grep $orasid >>/dev/null

hii..
It goes something like this..
i want to list a oracle database instance (say orasid=tiger) using this command..
I issued each command in separate and could understand little bit..
1. ps -ef :: lists all running processes
2. the output is directed to “grep -v grep” now
3. what that command does is just filter out any text containing ‘grep’..
4. this output is now sent to “grep $orasid”
5. it will just fetch only those running process like ” tiger ”
6. the output is redirected to /dev/null where the output is just discarded..
after this command here they used
if[ $? -ne 0]
then ————–
else —————–
fi
where $? reads output of previous command…
here $? is 0 as the command hasn’t thrown any error

Dear All ,
Thnaks for this nice chart it helps me a lot .
1- If i need to search for a “word” inside a directory that holds files, these files are located in the “www”
2- Also to search for a “word” in the all the databases in : /var/lib/mysql/database

Thanx all

@ed
use
# grep ^[A-Z][A-Z] [0-9] [0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9]$ filename

i hope it work………

Hi i wud like an explanation of the ff command
grep[a-g]…[r-z]text.txt

@ Syed:

** answer1 **
cat file | grep '^cc:$'
will produce only cc: with no value.
Learn regular expressions. In the command above regular expression is between ”. So… cat is normal command that prints file. Then result is piped (|) to grep, which processes it with regular expression (^cc:$).
This regex basically matches lines, which contain:
^ – beginning of the line
c – letter c
c – letter c
: – colon
$ – end of line
If there is something between colon (:) and end of line ($), in your case some value, then line is not produced by grep.

** answer2 **
How to check value of aa: in the record which contain dd:uvw?
cat file | grep -B3 'dd:uvw'
-B3 tells grep to show line that matches our pattern and 3 lines Before (you can change this number if you want, you can use -A4 to show 4 lines After).
So the command above will produce whole 4 line of each record, which contain dd:uvw. To show only lines with aa: and their values, we can simply add subsequent grep:
cat file | grep -B3 'dd:uvw' | grep 'aa'
…and that’s it.

@ jyothi
ps -ef|grep -v grep|grep $orasid » /dev/null

Explanation:
ps -ef lists processes. On that list there is number of every process, even number of grep process executed in this line. For example if i try to grep non-existing process john by issuing command ps -ef | grep john, then i will get this:
dev 6271 5933 0 05:43 pts/0 00:00:00 grep john
Even if there is no process I am looking for, I will get result from grep. I don’t want that to happen, so I will have to grep invert match (grep -v pattern as explained in the howto above).
In other words ps -ef | grep -v grep will list processes excluding grep.

After next pipe you have:
grep $orasid
$string recalls value of variable defined before.
If you define $orasid=bob, then your command will be equal to:
ps -ef | grep -v grep | grep bob » /dev/null
If $orasid=william, then your command will be equal to:
ps -ef | grep -v grep | grep william » /dev/null
and so on…

» /dev/null redirects output of the command to nowhere, because we don’t want to see grep output on our screen, when executing the code.

Summarizing:

$orasid=tiger
...
ps -ef | grep -v grep | grep $orasid >> /dev/null
...
if [ $? -ne 0]
then echo 'claws'
else echo 'no claws'
fi


If there is process named tiger (output of grep is not empty), then we get claws, else we get no claws :)

very useful to me..

Simply super ,,,thanks

Reply to Shan
wel u can use
grep -iw hello filename
if two words ex. Hello and
Hi, use foll syntax
egrep -iw ‘hello|Hi filename

Hi
I have an outstanding issue with me…
i know the specific pattern in the file but dont know the name of the file/script and dont know the location either.
How to search the filename with simply the pattern in that file.

Actually at some xyz location a .dmp file gets created (xyz.dmp (everyday it creates the same file as it a daily backup.))…now i dont know which script creates this .dmp file…So i need to know the name of the script.

@Hammy

In order to count “words” , “characters” and “lines” in a file there is a bash command called “wc”.

example:

wc -l < filename
or
cat filename | wc -l
will count number of lines in file named "filename"

wc -w < somefile
cat somefile | wc -w
will count number of words or strings in the file named "somefile"

wc -c < somefile
cat somefile | wc -c
will count number of characters in the file named "somefile"

cheers!!