Run Time Help

highest memory consuming process ?
ps -m -O %mem -u user_name | sort -nr | head -10
ps -m -O %cpu -u user_name | sort -nr | head -10

$ ps aux  
USER       PID  %CPU %MEM  VSZ RSS     TTY   STAT START   TIME COMMAND
timothy  29217  0.0  0.0 11916 4560 pts/21   S+   08:15   0:00 pine  
root     29505  0.0  0.0 38196 2728 ?        Ss   Mar07   0:00 sshd: can [priv]   
can      29529  0.0  0.0 38332 1904 ?        S    Mar07   0:00 sshd: can@notty  

• USER = user owning the process
• PID = process ID of the process
• %CPU = It is the CPU time used divided by the time the process has been running.
• %MEM = ratio of the process’s resident set size to the physical memory on the machine
• VSZ = virtual memory usage of entire process (in KiB)
• RSS = resident set size, the non-swapped physical memory that a task has used (in KiB)
• TTY = controlling tty (terminal)
• STAT = multi-character process state
• START = starting time or date of the process
• TIME = cumulative CPU time
• COMMAND = command with all its arguments

In Linux the command:

ps -aux

Means show all processes for all users. You might be wondering what the x means? The x is a specifier that means 'any of the users'. So you could type this:

ps -auroot

Which displays all the root processes, or

ps -auel

which displays all the processes from user el. The technobabble in the 'man ps' page is: "ps -aux prints all processes owned by a user named 'x' as well as printing all processes that would be selected by the -a option.

how to schedule perl prog without crontab ?
batch / at

Schedule an at job using specific date and time
at time date
at 11 am may 20
at now + 1 min
at now + 1 day

$ at -f myjobs.txt now + 1 hour
at 10 am tomorrow

$ at 11:00 next month

$ at 22:00 today

$ at now + 1 week

$ at noon

modules used in perl - WWW::Mechanize, Data::Dumper, File::Path, File::remove, File::Spec - to run linux cmnds on windows

How to find third or nth maximum salary from salary table?

N minimum salary:
SELECT MIN(EmpSalary)
FROM Salary
WHERE EmpSalary IN(SELECT TOP N EmpSalary FROM Salary ORDER BY EmpSalary DESC)

for Ex: 3 minimum salary:

SELECT MIN(EmpSalary)
FROM Salary
WHERE EmpSalary IN(SELECT TOP 3 EmpSalary FROM Salary ORDER BY EmpSalary DESC)

N maximum salary:

SELECT MAX(EmpSalary)
FROM Salary
WHERE EmpSalary IN(SELECT TOP N EmpSalary FROM Salary ORDER BY EmpSalary ASC)

for Ex: 3 maximum salary:

SELECT MIN(EmpSalary)
FROM Salary
WHERE EmpSalary IN(SELECT TOP 3 EmpSalary FROM Salary ORDER BY EmpSalary ASC)

select * from (
  select Emp.*,
row_number() over (order by Salary DESC) rownumb
from Employee Emp
)
where rownumb = n;  /*n is nth highest salary*/



tr is an UNIX utility for translating, or deleting, or squeezing repeated characters. It will read from STDIN and write to STDOUT.

tr stands for translate.

Syntax

The syntax of tr command is:

$ tr [OPTION] SET1 [SET2]
Translation

If both the SET1 and SET2 are specified and ‘-d’ OPTION is not specified, then tr command will replace each characters in SET1 with each character in same position in SET2.

1. Convert lower case to upper case

The following tr command is used to convert the lower case to upper case

$ tr abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ
thegeekstuff
THEGEEKSTUFF
The following command will also convert lower case to upper case

$ tr [:lower:] [:upper:]
thegeekstuff
THEGEEKSTUFF
You can also use ranges in tr. The following command uses ranges to convert lower to upper case.

2. Translate braces into parenthesis

You can also translate from and to a file. In this example we will translate braces in a file with parenthesis.

$ tr '{}' '()' < inputfile > outputfile
The above command will read each character from “inputfile”, translate if it is a brace, and write the output in “outputfile”.

3. Translate white-space to tabs

The following command will translate all the white-space to tabs

$ echo "This is for testing" | tr [:space:] '\t'
This is for testing

4. Squeeze repetition of characters using -s

In Example 3, we see how to translate space with tabs. But if there are two are more spaces present continuously, then the previous command will translate each spaces to a tab as follows.

$ echo "This   is   for testing" | tr [:space:] '\t'
This is for testing
We can use -s option to squeeze the repetition of characters.

$ echo "This   is   for testing" | tr -s [:space:] '\t'
This is for testing
Similarly you can convert multiple continuous spaces with a single space

$ echo "This  is  for testing" | tr -s [:space:] ' '
This is for testing

5. Delete specified characters using -d option

tr can also be used to remove particular characters using -d option.

$ echo "the geek stuff" | tr -d 't'
he geek suff
To remove all the digits from the string, use

$ echo "my username is 432234" | tr -d [:digit:]
my username is
Also, if you like to delete lines from file, you can use sed d command.

6. Complement the sets using -c option

You can complement the SET1 using -c option. For example, to remove all characters except digits, you can use the following.

$ echo "my username is 432234" | tr -cd [:digit:]
432234

7. Remove all non-printable character from a file

The following command can be used to remove all non-printable characters from a file.

$ tr -cd [:print:] < file.txt

8. Join all the lines in a file into a single line

The below command will translate all newlines into spaces and make the result as a single line.

$ tr -s '\n' ' ' < file.txt