CODEWITHSUNDEEP
cunix
Spyros_av
Spyros_av

Reputation: 893

Handle commands like ls -l /somedir

My code so far handles the ls command when the user types it. I want to be able to handle commands like ls -l /tmp . My code so far.

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <stdarg.h>
#include <sys/types.h>


int main(void)
{
for(;;){
char str[500];
printf("Type a command : \n");
scanf("%s",str);
char *path;
  path = getenv("PATH");
    char *argv[] = { path ,NULL};

    int status;
    int pid = fork();

        if ( pid == 0 ) {
printf("executing==============> %s \n",str);
          execvp(str,argv);
}
wait(&status);
}
}

Any ideas? I have to do it without system().

Upvotes: 1

Views: 126

Answers (4)

Spyros_av
Spyros_av

Reputation: 893

This worked for me:

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <stdarg.h>
#include <sys/types.h>
#define MAX_NAME_SZ 256

int main(void)
{
char *str,*ret, *pa1, *pa2, *dtm ,*pa3;
str=(char *)malloc(50*sizeof(char));
ret=(char *)malloc(50*sizeof(char));
pa1=(char *)malloc(50*sizeof(char));
pa2=(char *)malloc(50*sizeof(char));
dtm=(char *)malloc(50*sizeof(char));
pa3=(char *)malloc(50*sizeof(char));
char ch =' ' ;
printf("Type a command : \n");

    fgets (str, MAX_NAME_SZ, stdin);

    if ((strlen(str)>0) && (str[strlen (str) - 1] == '\n'))
        str[strlen (str) - 1] = '\0';
    ret = strchr(str, ch);

    if (ret !=NULL)
    {
        strcpy( dtm, str );
        sscanf( dtm, "%s %s %s  ", pa1, pa2,pa3  );
        }

    char *path;
     path = getenv("PATH");

    int status=2;
    int pid = fork();

    if ( pid == 0 ) {
        if (ret !=NULL){
          char *argv[] = { path ,pa2, pa3 ,NULL};
              execvp(pa1,argv);

                }
        else {
          char *argv[] = { path ,NULL};
          execvp(str,argv);

        }
    }
    wait(&status);

    }

Upvotes: 0

Siddharth
Siddharth

Reputation: 321

Use "system" function for the same. system(str) should probably work. This function creates a separate thread, executes the command provided to it. See 'man system' for details of it.

Upvotes: 0

jofel
jofel

Reputation: 3405

You can do this and comparable things easily with system(str).

It forks, calls execl("/bin/sh", "sh". "-c", command, (char *) 0); and returns after the command has completed.

As it calls the shell, it support also the shell built-ins.

Upvotes: 1

ddz
ddz

Reputation: 526

The execvp system call expect as its parameters a string with the command and an array of strings starting with the command, followed by its parameters, one by one, and ending with a NULL string.

In your case, it would be:

char *argv[] = {"ls", "-l", "/tmp", NULL};

Remember that this piece of code is just an illustration of what is behind the scenes. You need to construct argv[] based on the user's input.

You can combine strchr() to tokenize your input (looking for blank spaces) and then using sscanf to read one part of the string. Then you have to update the input pointer to the value returned by strchr() + 1 and use sscanf() to read the next part of the command.

Upvotes: 2

Related Questions