execlp command syntax help

tonyfreeman · 09-02-2004, 10:05 AM

I'm forking a process to run a backup command. I've been trying to figure out how to use one of the "exec" commands to do the equivalent of the code below:

Code:

tar czf /tmp/2004Sep01.tar.gz `find /data/local/2004/Sep/01 -daystart -cmin +1420 -cmin -2290`

. . . but I'm having trouble figuring this out.

To start out, I've tried to figure out how to just do the find command part, but this attempt doesn't work:

Code:

#include <stdio.h>
#include <stdlib.h>
#include <glib.h>
int main () {
  g_print("Executing command\n");
  execlp("find", "find", "/data/local/2004/Sep/01", "-daystart", "-cmin", "+1000", "-cmin", "+2000", ">/tmp/find.text", NULL);
  g_print("End of command\n");
  return EXIT_SUCCESS;
}

Could you please help me figure out how to properly use one of the "exec" commands to do what I want?

Possibly running a tar/find command isn't what I should be doing? Is there a "C" way to do it?

--Tony

KneeLess · 09-02-2004, 01:25 PM

man 3 exec

One thing I noticed is that the first arguement of execlp() is the filename of the file to be executed, maybe use the full pathname (/usr/bin/find). And I don't believe you need the "find" twice, just once will do.

tonyfreeman · 09-02-2004, 01:39 PM

OK ... I just figured out that if I removed the ">/tmp/find.text" part .... the find command works.

Code:

execlp("find", "find", "/data/2004/Sep/01", "-daystart", "-cmin", "+1000", "-cmin", "+2000", NULL);

I wonder why it didn't like sending the output to the text file?

Anyway ... Now I need to adjust things in order to make the tar command run off of the find command.

Has anyone done this sort of thing before? Any ideas or examples I can use to do it?

Thanks for reading ;-)

--Tony

KneeLess · 09-02-2004, 01:41 PM

Quote:

I wonder why it didn't like sending the output to the text file?

As far as I know, execlp() doesn't use bash, which I should've seen, and the last part is bash syntax.

mirradric · 09-02-2004, 08:54 PM

Quote:

One thing I noticed is that the first arguement of execlp() is the filename of the file to be executed, maybe use the full pathname (/usr/bin/find). And I don't believe you need the "find" twice, just once will do.

You do need to have find twice, once for the program to execute and the second for the the zero argument (i.e. the name of the program).

And you don't need to use the full pathname if the command is in your path. The p family does it for you.

If you need to redirect the output then use dup2 to change the stdout to that of a file descriptor of a file.

heluani · 09-07-2004, 09:09 AM

If you type at command prompt

~[1]$ mybin -myarg > mypath/myfile

Then mybin is executed with only two arguments (agrv[0]="mybin" and argv[1]="-myarg") and the shell takes care of the rest. You were sending "> mypath/myfile" as an argument to "mybin" who doesn't understand that. You should redirect the output before or in the case of find, send a parameter like "-fprintf", look at the man page for find.

R.