Unix shell script to get cpu usage

Unix shell script to get CPU usage

#!/bin/bash

id=0; tot=0; p_id=0; p_tot=0;

for ((i=0; $i < 100; ++i )) ; do

    p_id=$id; p_tot=$tot;
    x=`cat /proc/stat | grep -w cpu`;
    id=`echo $x | cut -d " " -f 5`;
    tot=0;
    for f in `echo $x`; do
        tot=$(($tot + $f));
    done;

    echo "idle CPU usage is % = "$((($id - $p_id)*100/($tot - $p_tot)));

    sleep 3;
done

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Unix shell script to kill a process by name

Unix shell script to kill a process by name

if [ "$1" == "" ];then
   echo "Usage : ./pkill.sh "
else
     for i in `ps ax | grep $1 | grep -v grep | sed 's/ *//' | sed 's/[^0-9].*//'`
        do
           kill -9 $i
        done
fi

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What are the Advantages of using UNIX with C ?

Well Friends as we know that C can do Much More Different with diferent OS but as best UNIX is cool whys its best partner of C ???? Lets Know....

Portability -- UNIX, or a variety of UNIX, is available on many machines. Programs written in standard UNIX and C should run on any of them with little difficulty.
Multiuser / Multitasking -- many programs can share a machines processing power.
File handling -- hierarchical file system with many file handling routines.
Shell Programming -- UNIX provides a powerful command interpreter that
understands over 200 commands and can also run UNIX and user-defined programs.

Pipe -- where the output of one program can be made the input of another. This can done from command line or within a C program.
UNIX utilities -- there over 200 utilities that let you accomplish many routines without writing new programs. e.g. make, grep, diff, awk, more ....
System calls -- UNIX has about 60 system calls that are at the heart of the operating system or the kernel of UNIX. The calls are actually written in C. All of them can be accessed from C programs. Basic I/0, system clock access are examples. The function open() is an example of a system call.
Library functions -- additions to the operating system.

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what is Debugging with GNU Debugger (GDB)

The debugger is the program that you use to figure out why your program isn’t behaving the way you think it should.You’ll be doing this a lot. The GNU Debugger (GDB) is the debugger used by most Linux programmers.You can use GDB to step through your code, set breakpoints, and examine the value of local variables.

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C header files in unix & its Working

You can learn a lot about the system functions that are available and how to use them by looking at the system header files.These reside in /usr/include and /usr/include/sys. If you are getting compile errors from using a system call, for instance, take a look in the corresponding header file to verify that the function’s signature is the same as what’s listed in the man page.
On Linux systems, a lot of the nitty-gritty details of how the system calls work are reflected in header files in the directories /usr/include/bits, /usr/include/asm, and /usr/include/linux. For instance, the numerical values of signals are defined in /usr/include/bits/signum.h.
These header files make good reading for inquiring minds. Don’t include them directly in your programs, though; always use the header files in /usr/include or as mentioned in the man page for the function you’re using.

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Prpgram to count vowels in given string by using vfork method (use of Vfork Function in c)

#include "stdio.h"
#include "dirent.h"
int main()
{
       int j,n,a,i,e,o,u;
       char str[50];
       a=e=i=o=u=0;
       pid_t pid;
       if((pid=vfork())<0)
        {
                perror("FORK ERROR");
                exit(1);
        }
        if(pid==0)
        {
                printf("Enter the String to count vowels:");
                gets(str);
                _exit(1);
        }
        else
        {
                n=strlen(str);
                for(j=0;j
                {
                        if(str[j]=='a' || str[j]=='A')
                                a++;
                        else if(str[j]=='e' || str[j]=='E')
                                e++;
                        else if(str[j]=='i' || str[j]=='I')
                                i++;
                        else if(str[j]=='o' || str[j]=='O')
                                                 o++;
                        else if(str[j]=='u' || str[j]=='U')
                                u++;
                }
                printf("Vowels Counting");
                printf("Number of A  : %d",a);
                printf("Number of E  : %d",e);
                printf("Number of I  : %d",i);
                printf("Number of O  : %d",o);
                printf("Number of U  : %d",u);
                printf("Total vowels : %d",a+e+i+o+u);
                exit(1);
        }
}

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