ls | wc command : Using ls|wc, we can count new lines, words and letters of all files of current directory. We can see from the following after execution of the code we get same results.
Prerequisites :ls command | wc command | piping in linux
Approach : First, we have to use pipe for inter process communication over an array where a[0] is used for reading and a[1] is used for writing. We can replicate the process using fork. In the parent process, standard output is closed so that output of ls command will go to a[0] and similarly standard input is closed in children process. Now, if we run the program output will be as same as command of linux ls|wc.
Below is the implementation of above approach :
// C code to implement ls | wc command #include <stdio.h> #include <stdlib.h> #include <fcntl.h> #include<errno.h> #include<sys/wait.h> #include <unistd.h> int main(){
// array of 2 size a[0] is for
// reading and a[1] is for
// writing over a pipe
int a[2];
// using pipe for inter
// process communication
pipe(a);
if (!fork())
{
// closing normal stdout
close(1);
// making stdout same as a[1]
dup(a[1]);
// closing reading part of pipe
// we don't need of it at this time
close(a[0]);
// executing ls
execlp( "ls" , "ls" ,NULL);
}
else
{
// closing normal stdin
close(0);
// making stdin same as a[0]
dup(a[0]);
// closing writing part in parent,
// we don't need of it at this time
close(a[1]);
// executing wc
execlp( "wc" , "wc" ,NULL);
}
} |