execute shell command inside of c code?

khucinx · 06-01-2004, 08:36 PM

i have c code like this :
#include<stdio.h>
#include<stdlib.h>
int main()
{
char *str;
printf("myshell-> ");
scanf("%s",str);
system("/bin/sh -c str");
return 0;
}
when i execute it, there is something error :
myshell-> ls
/bin/sh: line 1: str: command not found
Segmentation fault

so, what should i do?

thank's

itsme86 · 06-01-2004, 09:37 PM

Changes are in red:

#include<stdio.h>
#include<stdlib.h>
int main()
{
char str[256], buf[256];
printf("myshell-> ");
scanf("%s",str);
sprintf(buf, "/bin/sh -c %s", str);
system(buf);
return 0;
}

towlie · 06-01-2004, 09:43 PM

I think on most linux systems,
the execve() or execvp() will work (try 'man execve' or 'man execvp').

I believe that you have to fork a child process to call these functions in, though.

also don't forget to allocate memory to str (which may be the
cause of segmentation fault).

leamassiot · 02-02-2006, 06:37 AM

o If your OS is:
- *nix => you should use "fork" + one of the "exec"'s familly functions,
fork: http://www.opengroup.org/onlinepubs/009695399/
exec*: http://www.opengroup.org/onlinepubs/009695399/
- win* => you should use "CreateProcess"
CreateProcess: http://msdn.microsoft.com/library/de...ateprocess.asp

o To build the command line you can also try (I do not know if the code works):

Code:

#include <string.h>
...

char * maf()
{
  char s_begin[20]="/bin/sh -c ";
  char s_end[256];

  scanf("%s", str);
  return strcat(s_begin, s_end);
};
...