ibanja
asked on
fork() question - why is pid always > 0
I have downloaded a Google scrapper from scroogle.org. The source code is at http://www.searchlores.org/nbbw.c
The problem I am having is that the pid does not == 0 so the execl function does not execute the snarf program. I am new to fork() and I am not sure why it might not be returning 0 here as the child process.
Any insights appreciated. Below is part of the forkit() function that is giving me problems with an arrow at the appropriate spot (--->):
strcat( resource, "&btnG=Google+Search" );
/* snarf is used to search Google. Depending on your cgi-bin permissions
situation, you may need an extra copy of snarf in the user's directory
who owns the cgi-bin. Otherwise, some cgi-bin wrappers won't see the
correct permissions on snarf and Apache will most likely abort with
a "Premature end of script headers" error. Google should receive a
reasonable user-agent from snarf or whatever is used, or the results
may return as charset ISO 8859-1 instead of UTF-8 */
pid = fork();
if( pid == 0 )
execl( "/usr/bin/snarf", "/usr/bin/snarf", "-nqm", resource, wdump, NULL );
else if( pid == -1 )
return;
else
---> wpid = pid; //****** evaluates true here. *******//
for( cnt = 1; cnt < 60; cnt++ )
{
usleep( 100000 );
retval = waitpid( -1, &status, WNOHANG );
if( retval == wpid )
return;
}
/* after 6 seconds, we still have no sign of returning */
kill( wpid, SIGKILL );
sleep( 1 );
remove( wdump ); /* remove if it's there; no harm done if it isn't */
}
/* __________________________
Thanks,
ibanja
The problem I am having is that the pid does not == 0 so the execl function does not execute the snarf program. I am new to fork() and I am not sure why it might not be returning 0 here as the child process.
Any insights appreciated. Below is part of the forkit() function that is giving me problems with an arrow at the appropriate spot (--->):
strcat( resource, "&btnG=Google+Search" );
/* snarf is used to search Google. Depending on your cgi-bin permissions
situation, you may need an extra copy of snarf in the user's directory
who owns the cgi-bin. Otherwise, some cgi-bin wrappers won't see the
correct permissions on snarf and Apache will most likely abort with
a "Premature end of script headers" error. Google should receive a
reasonable user-agent from snarf or whatever is used, or the results
may return as charset ISO 8859-1 instead of UTF-8 */
pid = fork();
if( pid == 0 )
execl( "/usr/bin/snarf", "/usr/bin/snarf", "-nqm", resource, wdump, NULL );
else if( pid == -1 )
return;
else
---> wpid = pid; //****** evaluates true here. *******//
for( cnt = 1; cnt < 60; cnt++ )
{
usleep( 100000 );
retval = waitpid( -1, &status, WNOHANG );
if( retval == wpid )
return;
}
/* after 6 seconds, we still have no sign of returning */
kill( wpid, SIGKILL );
sleep( 1 );
remove( wdump ); /* remove if it's there; no harm done if it isn't */
}
/* __________________________
Thanks,
ibanja
ozo
Is it possible the pid is 0 and the execl is failing?
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ASKER
Thanks,
That makes it clear. Ironically I awoke at 2:00am this morning with this realization - that the child process may still be running the execl() function and that I am debugging in the parent process. I appreciate the input. I am finally understanding the nature of fork().
ibanja
That makes it clear. Ironically I awoke at 2:00am this morning with this realization - that the child process may still be running the execl() function and that I am debugging in the parent process. I appreciate the input. I am finally understanding the nature of fork().
ibanja