why is cpu usage code not working?

[kits]

#!/bin/bash

echo "Enter the process id"
read pid
ps aux | awk '/$pid/ && !/awk/ {print "%CPU usage is:", $3}'
ps aux | awk '/$pid/ && !/awk/ {print "%Mem usage is:", $4}'

i'm a linux newbie and also new to shell scripting.
the thing i'm working on:find cpu usage and mem usage when pid of a process is given
why is this not working?
when i give the pid, it returns to command prompt.

could yu pelase tell me whats wrong with this thing?
and also correct it if possible

if i want to know the cpu usage and mem usage for every 5 secs...
how do i loop it?

thanks in advance

[kits]

#!/bin/bash

echo "Enter the process id"
read pid
ps aux |grep $pid |awk '{print "%CPU usage is:", $3}'
ps aux |grep $pid| awk '{print "%Mem usage is:", $4}'

but it is showing the cpu usage of grep also....
what should i do to get only for the pid?

[vsemaska]

Do a grep a 2nd time to exclude grep (-v option)

echo "Enter the process id"
read pid
ps aux |grep $pid |grep -v grep| awk '{print "%CPU usage is:", $3}'
ps aux |grep $pid |grep -v grep| awk '{print "%Mem usage is:", $4}'

[Cabhan]

Or, rather than grepping, you can select by ps's built-in PID selecting:

echo "Enter the process id"
read pid
ps up $pid | awk '{print "%CPU usage is:", $3}'
ps up $pid | awk '{print "%Mem usage is:", $4}'

In ps, the 'u' means "user-oriented format", and the 'p' means "Only those PIDs that I specify".

[kits]

hey thanks cabhan and vsemaska

actually this thing also works:same thing as vsemsaka's

ps aux | grep $pid | awk '{print "% CPU usage of", $2 " is: ", $3}' | grep $pid
ps aux | grep $pid | awk '{print "% MEM usage of", $2 " is: ", $4}' | grep $pid

i have another doubt:
i tried to use these in c program and used system() function and included stdlib.h
then i wrote a simple program:
from:Process Control: <stdlib.h>,<unistd.h>

printf("the files are");
system("ls -l");

when i tried executing it ..it says 'permission denied'

so i gave this command: chmod a+x check.c

now it is showing syntax errors(though there arent any)

./check.c: line 7: syntax error near unexpected token `"the files are"'
./check.c: line 7: `printf("the files are");'




why is that so??what can i do to execute it??

[Juan Pablo]

You need to compile it first,

gcc -o check check.c

Then run ./check

[kits]

ok thanks juan pablo ...
>its running but then it is showing the files first and then it is printing
"the files are:"

i mean it is executing system() thing first and then printf...??!!

>how can i include the cpu usage code mentioned before in a c program..
system() wont work...

it says "segmentation fault"

[kits]

ok i cant use windows APIs.i actually got that with windows APIs.
but...
i've to wap in c in unix/linux. and all i could find regarding pids is
getpid() which returns only the pid of the process calling it.

so how can i get the cpu usage of a single process (when pid is given as input) ??

[Cabhan]

In regards to the output question: output is generally buffered, as this results in fewer writes from the program. This means that the program will store up a bit of output and then write it all at once. Generally, once you write a '\n', the output will flush. Alternatively, you can use fflush(FILE *) to flush a particular file. Try that with stdout.

As for finding CPU usage, check out the /proc directory. This contains a great deal of information on every running process.