exec and buffered output

Hello everyone, :(

I need some help please. Any appreciated. I don't know if I am having a memory lapse or what, but I can not seem to remember something.

I am using an exec call to execute a command, and that works fine and dandy, but I need to direct the output of this into a buffer, instead of stdout (onto the screen). Does anyone know how to do this?

-Optimus

Hello,

I just read about freopen last night.

From man freopen

Code:

---

SYNOPSIS
    #include <stdio.h>

    FILE *freopen(const char *filename, const char  *mode,  FILE
    *stream);

DESCRIPTION
    The freopen() function first attempts to  flush  the  stream
    and  close  any  file  descriptor  associated  with  stream.
    Failure to flush or close the file successfully is  ignored.
    The  error  and  end-of-file  indicators  for the stream are
    cleared.

    The freopen() function opens the file whose pathname is  the
    string  pointed  to  by  filename  and associates the stream
    pointed to by stream with it. The mode argument is used just
    as in fopen(3C).
USAGE
    The freopen() function is typically used to attach the preo-
    pened  streams  associated  with stdin, stdout and stderr to
    other files. By default stderr is unbuffered, but the use of
    freopen() will cause it to become buffered or line-buffered.

---

I think this might be what you want.
Hope it works,
Rouss

What about popen()

The popen function looks interesting. Can it take inside it though an excecvp call? I noticed this code at one site:

#include <stdio.h>
#include <stdlib.h>
main()
{
char *cmd = "/usr/bin/ls *.c";
char buf[BUFSIZ];
FILE *ptr;

if ((ptr = popen(cmd, "r")) != NULL)
while (fgets(buf, BUFSIZ, ptr) != NULL)
(void) printf("%s", buf);
(void) pclose(ptr);
return 0;
}

I am not sure if I can stick an execvp in there somewhere. This looks very promising though. Any comment apprecaited.

-optimus

Why would you need an exec call?
That loop executes the 'ls' command and collects its output one line at a time through calls to fgets()
It prints it, but there's nothing to stop you storing it in memory

I should have mentioned I am forced to use an exec call to take any command argument to run it. I need to store the output in a buffer though, and not on the screen.

V/r

optimus