subprocess to C program

Grant Edwards grante at visi.com
Sun Dec 14 02:51:23 CET 2008


On 2008-12-14, MRAB <google at mrabarnett.plus.com> wrote:

>> 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.

They certainly aren't in Unix: Their a property of the process.

-- 
Grant



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