Thread: popen debug

we call popen function repeat, sometime it work well,sometime it is wrong. when it work well , we get the command line execute filename;
when it is wrong , we get the result "s_path_name[i]=(%o)" : (0) (0) (0) (0 ) (0). we get the result (114) (116) ...(12) (0) when it work well.

if you check the fp , you will find that "fp[0]=%ld" : (537303080) when it work well, (537303072) when it is wrong.

the c code below:
sprintf( s_command, "/usr/bin/ps -p %ld |/usr/bin/awk '$1 == %ld {print$4}'", pid, pid );

if( ( fp = popen( s_command, "r" ) ) == NULL )
{
return( FATAL );
}

fscanf( fp, "%s", s_path_name );
for ( i_count=0; i_count<=10; i_count++ )
fprintf( stderr, "(%ld)", fp[i_count] );
for ( i_count=0; i_count<=10; i_count++ )
fprintf( stderr, "(%o)", s_path_name[i_count] );
if ( pclose( fp ) == -1 )
fprintf( stderr, "\n the pclose error");

popen? Never heard of that. Change it to fopen

The syntax is exactly the same as fopen. For example:

Code:

char string[10][30];
fptr = fopen(filename,"r"); if(fptr == NULL) exit(1);
while (fscanf(fptr,"%s",string[i]) != NULL)
{
   ++i
   if(i > 10) break;
}
fclose(fptr);
for(i=0;i<10;i++) printf("%s\n",string[i]);

our platform is AIX4.3. i think this problem is a system environment fault or memory fault.

but i don't know how to correct it. in fact i make a small c program to test popen, in 100000 call, no fault disappear.

sprintf( s_command, "/usr/bin/ps -p %ld |/usr/bin/awk '$1 == %ld {print$4}'", pid, pid );

I don't understand this too well because I use a Windows 2000 Professional. You might want to try posting this on the Linux programming board.

If the scan was successful it would return the number of sucessful scans, for example:

int status = fscanf(fptr, "%s%s%d", sting1,string2,&number);

This would return '3' if the scan was sucessful. But all this information should be in the prototype.

Maybe you should post your whole code. I think that Salem is in a better position to answer the question because he uses a *NIX operating system, but just post the whole code or you might never get a full answer.