It appears that the underlying globus jars don't read X509_USER_PROXY env variable, or that option is not enabled by pegasus-gridftp

Here is what I tried

corbusier:pegasus vahi$ grid-proxy-info
subject : /DC=com/DC=DigiCert-Grid/O=Open Science Grid/OU=People/CN=Karan Vahi 1633/CN=1144022931
issuer : /DC=com/DC=DigiCert-Grid/O=Open Science Grid/OU=People/CN=Karan Vahi 1633
identity : /DC=com/DC=DigiCert-Grid/O=Open Science Grid/OU=People/CN=Karan Vahi 1633
type : RFC 3820 compliant impersonation proxy
strength : 512 bits
path : /tmp/x509up_u3520
timeleft : 11:58:38
corbusier:pegasus vahi$ pegasus-gridftp mkdir -f -p gsiftp://obelix.isi.edu/tmp/karan

The above works
However, if i move my proxy and set X509_USER_PROXY environment variable the tool does not pick up the value.

corbusier:pegasus vahi$ mv /tmp/x509up_u3520 /tmp/proxy
corbusier:pegasus vahi$ export X509_USER_PROXY=/tmp/proxy
corbusier:pegasus vahi$ pegasus-gridftp mkdir -f -p gsiftp://obelix.isi.edu/tmp/karan
ERROR: mkdir failed
Unable to load user proxy
Defective credential detected [Caused by: [JGLOBUS-5] Proxy file (/tmp/x509up_u3520) not found.]
corbusier:pegasus vahi$