Simple Shell

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <signal.h>
#include <link.h>
#include <sys/wait.h>
#include <errno.h>
#include <myPipe.h>
#include <tokenize.h>
#include <myCD.h>


int main(){

    char input_line[256];   //input line
        char *command[100];    

 
while (1) {   //print consegatively the shell until the user press "exit"
//char *path[100];
//getcwd(path, 100);
//printf("\n[MY_SHELL ] %s ", path);
printf("\n[MY_SHELL ]");
        fgets(input_line,sizeof(input_line),stdin);
        input_line[strlen(input_line)-1] = '\0';
 

//if user wants to exit from the current shell

if(strstr(input_line,"exit")!=NULL) {    
exit(0);     //exit from the shell
}


//if user wants to direct to another directory
else if(strstr( input_line,"cd")!=NULL) //if user uses "cd" command to change the directory
{
myCD(input_line);//run myCD method
}

else if(strstr( input_line,"$PATH")!=NULL){
printf("path: %s \n",getenv("PATH"));
}
//if user asks for pipe function

else if(strstr(input_line,"|")!=NULL){
myPipe(input_line);//run pipe method
}
else{
 
tokenize(input_line, command);
//use the execvp function to run the process i.e the user's command
if(!fork()){
if (execvp(command[0],command) == -1)
{
  printf("Command not found\n");
}
     }else{
wait(NULL);
}
}
}
return 0;

}

myPipe



void myPipe(char *input_line){

  int temp;
  int index=0;

for(temp = 0; temp < strlen(input_line); temp++){
if(input_line[temp] == '|'){
index=temp;
break;
}
}


char one[128];
      char two[128];
  int len=strlen(input_line);

strncpy(one, input_line, index);
one[index] = '\0';


//Copying two characters from the middle of string S to D:
//strncpy(two, &string[5], 2);
strncpy(two, &input_line[index+1], (len-index+1));
two[len-index-1] = '\0';



int pfds[2];
pipe(pfds);
if (!fork()) {
close(1); /* close normal stdout */
dup(pfds[1]); /* make stdout same as pfds[1] */
close(pfds[0]); /* we don't need this */
execlp(one,one , NULL);

}
  else {
close(0); /* close normal stdin */
dup(pfds[0]); /* make stdin same as pfds[0] */
close(pfds[1]); /* we don't need this */
execlp(two,two , NULL);

}

}

tokenize

void tokenize(char *input_line, char **z)

{ 

    int x = 0; //used to continue through the array

    int a = 0;

    char *tray[100]; //to keep elements that are tokanized

tray[a] = strtok(input_line, " "); //get pointer to first token and store in 0 place in array

      

    while(tray[a]!= NULL){  //make sure a pointer is found

    a++;

    tray[a] = strtok(NULL, " "); //continue to tokenize the string

}

for(x = 0; x< a; x++){ //for loop to assign tokenz in to an array

z[x] = tray[x];

}

z[a] = NULL;

}

myCD

char *cdir[100];   

int dec;

void myCD(char *input_line){

//create a char pointer array to be passed to the chdir function

//tokenize the command enter by user

  tokenize(input_line, cdir);

//pass the first element of the pointer arrat to the chdir function

    dec=chdir(cdir[1]);

  if(dec==-1){

printf("No such file or directory\n");//continue;

    }

}

PS
myPipe, tokenize and myCD included as header files. If someone wants to make use of this code, save them in separate 3 files and run the main code

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