Internet is a worldwide system of computer networks which connects more than thousands of computers in which the users at any of the one computer can, if they have permission, get information from any other computer.
Usually named as "net ''.
If you want to use floating for a 3-column page layout that consists of an aside, a main element, and another aside, you need to
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/ to access the input scanf()
// and output printf()
#include <stdio.h>
// to access the functions like
// pipe(), fork(), execvp(), dup2()
#include <unistd.h>
// to access the string functions like
// strtok()
#include <string.h>
// to access function wait()
#include <sys/wait.h>
#include <stdlib.h>
int main()
{
// declare a variable to hold the process id
pid_t p_id;
// declare a variable to hold the index value
int array_index;
// declare the string to hold the user input
// as command
char userIn_Command[128];
// use a continuous loop
while (1)
{
// display the prompt for the user
printf("minor5> ");
// read the input from the user
scanf("%[^\n]", userIn_Command);
// check the condition that whether the user
// inputs a command called "quit"
// If the user inputs quit command then exit from
// the script
if (strcmp(userIn_Command, "quit") == 0)
{
printf("\n");
break;
}
// if there are any usage of pipelining or redirection
// display the error message and exit from the script
if (strchr(userIn_Command, '|') != NULL || strchr(userIn_Command, '>') != NULL ||
strchr(userIn_Command, '<') != NULL)
{
printf("Error: Cannot perform the multiple command operations or directions\n");
break;
}
// declare the variables to hold the process
int p_pids[2];
// create the system call to pipe() from kernal
// and display the error message
if (pipe(p_pids) < 0)
{
printf("Error: Pipe creation failed!\n");
}
// create the child process
p_id = fork();
// condition to check whether the fork() is
// created. If so, display an error message
if (p_pids < 0)
{
printf("Error: fork() failed!\n");
break;
}
// if the child process is created
if (p_id == 0)
{
// close pipe in child process
close(p_pids[0]);
// create duplicate of the standard output
dup2(p_pids[1], STDOUT_FILENO);
// close the pipe in child process
close(p_pids[1]);
// declare a variable to store path
// to execute the command
char *command_path;
// declare an array of string to hold the options
char * args[32];
// tokenize the command by using the delimiter at " "(single space)
char *cmd_token = strtok(userIn_Command, " ");
// store the token value
command_path = cmd_token;
args[0] = cmd_token;
array_index = 1;
// loop until all the options in the command are
// tokenized
while (1)
{
// get the next token
cmd_token = strtok(NULL, " ");
// condition to check whether the token is null
// or not
if (cmd_token == NULL)
{
break;
}
// store the token if it is not null
args[array_index] = cmd_token;
// increment the index
array_index++;
}
// last parameter to the command should be NULL */
args[array_index] = NULL;
/* calling exec function with command path and parameters */
if (strcmp(args[0], "cd") == 0 || strcmp(args[0], "history") == 0 ||
strcmp(args[0], "exit") == 0)
{
printf("%s: Command not found\n", args[0]);
break;
}
if (execvp(command_path, args) < 0 )
{
printf("%s: Command not found\n", args[0]);
break;
}
}
else
{
/* closing writing end of pipe in parent process */
close(p_pids[1]);
/* reading ouput written to pipe in child process and
* writing to console */
while (1)
{
char output[1024];
int n = read(p_pids[0], output, 1024);
if (n <= 0)
{
break;
}
output[n] = '\0';
printf("%s", output);
}
/* closing read end of pipe1 */
close(p_pids[0]);
/* waiting until child process complete its execution */
wait(NULL);
}
/* skipping newline character read while scanf() */
getchar();
}
exit(0);
}
Explanation:
