exec question

exec question

[ework0]

Hello,

How can I execute a program (without the full path, just the name) using 
exec's system calls within a C program? ej: buf[]={"uname",NULL};

Thanks for a brief example,

ework0

Re: exec question

[davidgn]

Quoting ework0 <ework0@gmail.com>:

> David Eduardo Gómez Noguera wrote:
> 
> >On Thu, 2005-11-03 at 23:09 -0600, ework0 wrote:
> >  
> >
> >>Hello,
> >>
> >>How can I execute a program (without the full path, just the name)
> using 
> >>exec's system calls within a C program? ej: buf[]={"uname",NULL};
> >>
> >>Thanks for a brief example,
> >>
> >>ework0
> >>
> >>
> >>    
> >>
> >
> >I think not, not with exec's family of functions anyway.
> >You could try system though, or popen or some other way, but its a bit
> >risky to call programs without the full path.
> >
> >  
> >
> are you sure DAVID!!! ???? I cant use system() or popen() is unsecure!
> 
> 


The reason you can avoid a full path with system and popen is because they first
spawn a shell and then have the shell execute the program. 
The shell first looks for the program in the PATH env variable.

Also to use exec you probably want to fork() first.

But then again, what does that buff variable is for? if it's ARGV, then its
right to have the name for the program only, but the filename argument still
needs to include the full path

i.e.

execv("/bin/uname", buff);

would execute /bin/uname, and if it happened to read it's first parameter
(argv[0]) it would find the string "uname"
there would also be no more parameters (argc == 1)

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Re: exec question

[Lawrence Bowie]

I believe this is what you want, right?

In the future, you will get a much more expedient response by posting to
the newsgroup, comp.unix.programmer. :) Just an FYI .. not trying to
scare you away.



#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int
main(int argc, char *argv[])
{
	/* In using execlp you better be sure PATH is set properly and
	 * also in ceratin situations it might be a security risk.
	 */
	/* Uncomment below if you want an example with arguments */
        //if (execlp("cat", "cat", "/etc/hosts", (char *)0) < 0)
        if (execlp("df", "df", (char *)NULL) < 0)
                fprintf(stderr, "\nCannot exec!\n");

        exit(0);
}

ework0 wrote:
> Hello,
> 
> How can I execute a program (without the full path, just the name) using
> exec's system calls within a C program? ej: buf[]={"uname",NULL};
> 
> Thanks for a brief example,
> 
> ework0
> 
> 
> -
> To unsubscribe from this list: send the line "unsubscribe
> linux-c-programming" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>