subprocess to C program

[MRAB]

Aaron Brady wrote:
> Hi,
> 
> I am writing a C process and I want to read data from a file that I
> write to in Python.  I'm creating a pipe in Python, passing it to the
> C process, and calling '_read'.  It gives me error 9, bad file number.
> 
> Python code:
> 
> import subprocess as s, os
> r, w= os.pipe( )
> os.write( w, 'abcdefghij\n' )
> a= s.Popen( [ r'C:\Documents and Settings\usr\Desktop\working
> \try_start', '%i'%r, '%i'%w ] )
> 
> C code:
> 
> char buf[ 16 ];
> memset( buf, 0, 16 );
> int readfd= atoi( argv[ 1 ] );
> int ct= _read( readfd, buf, 15 );
> printf( "\n\n'_read %i %i %i': %s\n", ct, readfd, errno, buf );
> 
> Output:
> 
> '_read -1 3 9'
> 
> meaning that 'ct' is -1, 'readfd' is 3, and 'errno' is 9.  I want 'ct'
> to be 11 at this point.  Thanks in advance.
> 
It looks like the ids aren't system global.