Like the C function rpmReadPackageFile, the Python API provides a convenient way to read in a header object from an RPM package file. The hdrFromFdno method reads an RPM header from an open file descriptor. The basic syntax is:

h = ts.hdrFromFdno(fdno)

Note

The hdrFromFdno method uses Python’s low-level file descriptors instead of the higher-level Python file objects. In the RPM C library, an FD_t is a FILE**. This could be bound to a Python class, but that is outside the scope of this chapter.

The following example shows a function that opens a file, reads in the RPM header, and then closes the file:

def readRpmHeader(ts, filename):

""" Read an rpm header. """

fd = os.open(filename, os.O_RDONLY)

h = ts.hdrFromFdno(fd)

os.close(fd)

return h

ts = rpm.TransactionSet()

h = readRpmHeader( ts, 'n-r-v.rpm' )

The hdrFromFdno method raises a number of exceptions based on issues detected with the package files. The following example shows these exceptions:

def readRpmHeader(ts, filename):

""" Read an rpm header. """

fd = os.open(filename, os.O_RDONLY)

h = None

tryL

h = ts.hdrFromFdno(fd)

except rpm.error, e:

if str(e) == "public key not available":

print str(e)

if str(e) == "public key not trusted":

print str(e)

if str(e) == "error reading package header":

print str(e)

h = None

os.close(fd)

return h

ts = rpm.TransactionSet()

h = readRpmHeader( ts, 'n-r-v.rpm' )

You can decide in your code whether the exceptions should stop processing or not.