Very Computer

Hi,

I want to call a command using C programmatically using execv, but I
also want to capture the standard output and standard error to files I
specify through command line args.  I want to use the file descriptors
0, 1, and 2 appropriately for this, and I understand I should probably
call a fork()
when calling the execv so my program can return successfully.  But
from there,
I'm not sure where to start.  I think I want to probably use dup2 so I
can redirect the descriptors to files I open.  Maybe create a pipe
from the child process to the parent process, where I pass through the
pipe are the results of the command call ??  Just need some guidance
and want to make sure I'm in the right direction.  Thanks.

comp.lang.c:

Quote:> Hi,

> I want to call a command using C programmatically using execv, but I
> also want to capture the standard output and standard error to files I
> specify through command line args.  I want to use the file descriptors
> 0, 1, and 2 appropriately for this, and I understand I should probably
> call a fork()
> when calling the execv so my program can return successfully.  But
> from there,
> I'm not sure where to start.  I think I want to probably use dup2 so I
> can redirect the descriptors to files I open.  Maybe create a pipe
> from the child process to the parent process, where I pass through the
> pipe are the results of the command call ??  Just need some guidance
> and want to make sure I'm in the right direction.  Thanks.

Please don't cross-post platform specific, non standard issues to
comp.lang.c.  You're just plain off-topic here, as none of execv(),
file descriptors, dup2(), fork(), pipes, or processes are defined or
supported by the standard C language.  They are extensions provided by
your particular compiler/OS combination.

Hint, in the future check the man pages.  If they don't say that the
function/data type/feature is ANSI, don't post it here.

--
Jack Klein
Home: http://JK-Technology.Com
FAQs for
comp.lang.c http://www.eskimo.com/~scs/C-faq/top.html
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alt.comp.lang.learn.c-c++ ftp://snurse-l.org/pub/acllc-c++/faq

What you want to do is an freopen() of the stdin, stdout, and
stderr after you fork() and before you exec().

--
Fletcher Glenn
to reply remove NOSPAM from my reply address

Quote:> Hi,

> I want to call a command using C programmatically using execv, but I
> also want to capture the standard output and standard error to files I
> specify through command line args.  I want to use the file descriptors
> 0, 1, and 2 appropriately for this, and I understand I should probably
> call a fork()
> when calling the execv so my program can return successfully.  But
> from there,
> I'm not sure where to start.  I think I want to probably use dup2 so I
> can redirect the descriptors to files I open.  Maybe create a pipe
> from the child process to the parent process, where I pass through the
> pipe are the results of the command call ??  Just need some guidance
> and want to make sure I'm in the right direction.  Thanks.