Perform other functions while untarring file using "system" command in a C program

[zoqix at yahoo.com (zoqix)]

thanks guys. I used the background function and it works. As for the fork(),
I'm not sure how do I use it and the exec() function.
any advise?

thanks again

----- Original Message -----
From: "Jerry Feldman" <gaf at blu.org>
To: "New York Linux User Group (z)" <nylug-talk at nylug.org>; "Boston Linux
Mail List - z" <discuss at Blu.Org>; "zoqix" <zoqix at yahoo.com>
Sent: Thursday, February 01, 2001 4:43 AM
Subject: Re: Perform other functions while untarring file using "system"
command in a C program


> The system(2) function by defnition waits until the command completes.
> As John mentioned, you could use the popen() function or you could do a
> fork()/exec() yourself. Also note that the GNU tar command with the z
> option forks a gzip(or gunzip) which then pipes the output file to tar.
>
> As a quick example:
> /* signal handler */
> void sighand(int sig)
> {
> if (sig == SIGCHLD) {
> finished = 1;
> }
> }
> pid_t chld = fork();
> finished = 0;
> set up signal to catch the SIGCHLD signal;
>
> if (chld == 0) {
> exec(tar command);
> return 0; /* or exit() */
> } else if (chld == -1) {
> perror("fork");
> exit(-1);
> } else { /* parent */
> do {
> /* calculate percent */
>   printf("%d %% Completed", percent);
> } while(! finished);
> }
> /* done */
>
>
>
> On 31 Jan 2001, at 13:04, John Abreau wrote:
>
> > On Wed, 31 Jan 2001, zoqix wrote:
> >
> > > Hi all,
> > > I'm using the "system" command to do an untarring of a file.tar.gz
file
> > > in my C program. However, I would like to display some status
> > > information like "10 % Completed". I've written some code to calculate
> > > the percentage. However, the code could only be runned after the
> > > "system" command finished untarring my zipped file. e.g.
> > >
> > > system("tar zxf file.tar.gz");
> > > do
> > > {
> > > printf("%d %% Completed", percent);
> > > }while (!finished)
> > >
> > > Therefore, the printf will always print 100 % Completed. Is there any
> > > way to let the unzipping continue at background and return to print
the
> > > completion status?
> > >
> >
> > A look through the info files for GNU tar shows the following:
> >
> > `--checkpoint'
> > This option directs `tar' to print periodic checkpoint
> > messages as it reads through the archive.  Its intended
> > for when you want a visual indication that `tar' is still
> > running, but don't want to see `--verbose' output.
> >
> > It doesn't give a percentage, and it's not immediately clear what the
> > number it does give actually represents, but it's probably a good
starting
> > point.
> >
> > To use its output, you'd have to replace the "system" call with a call
to
> > popen that reads from the stdout of the "tar" process. You'd also want
to
> > change the buffering of data in the pipe so you can immediately read the
> > output from tar at the newline, rather than waiting for a complete block
> > to be buffered.
> >
> > --
> > John Abreau / Executive Director, Boston Linux & Unix
> > ICQ#28611923 / AIM abreauj / Email jabr at blu.org
> >
> > -
> > Subcription/unsubscription/info requests: send e-mail with
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> > message body to discuss-request at blu.org (Subject line is ignored).
>
>
> Jerry Feldman <gaf at blu.org>
> Associate Director
> Boston Linux and Unix user group
> http://www.blu.org
> -
> Subcription/unsubscription/info requests: send e-mail with
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