I ran into a minor buglet this morning - when curl tries to download a zero length file using sftp, it says it did the download but it but never creates the file locally. I'm running curl on an AIX system and I've tested it against sftp servers running on AIX, Linux and Ipswitch's MOVEit EZ server. I see a "File already completely downloaded" message in the --verbose output but the file doesn't exist on the local host after curl finishes and the curl's exit status is 0. I never would have noticed this except that MOVEit is so finicky that it causes curl to return an error when it tries to delete the file with a -Q "-rm ...." command option. (The QUOTE delete is part of the original script that I left off of the example below to simplify things.)

I see in libcurl a couple of years back there were some fixes put in for zero length files for http: protocol. (See http://curl.haxx.se/mail/lib-2008-11/0134.html) Is this the same problem for sftp & ftp?

Here's the output from a short shell script showing the problem:

/bin/curl -V
curl 7.21.3 (powerpc-ibm-aix5.1.0.0) libcurl/7.21.3 OpenSSL/0.9.8o zlib/1.2.4 libidn/1.19 libssh2/1.2.7
Protocols: dict file ftp ftps gopher http https imap imaps pop3 pop3s rtsp scp sftp smtp smtps telnet tftp

/bin/curl -u uid:pwd -v --key /home/jay/.ssh/id_dsa --pubkey /home/jay/.ssh/id_dsa.pub -O --url sftp://vtd//tmp/jay
Features: IDN IPv6 Largefile NTLM SSL libz
* About to connect() to vtd port 22 (#0)
* Trying 198.185.205.10... % Total % Received % Xferd Average Speed Time Time Time Current
                                 Dload Upload Total Spent Left Speed
  0 0 0 0 0 0 0 0 --:--:-- 0:00:01 --:--:-- 0connected
* Connected to vtd (198.185.205.10) port 22 (#0)
* Failed to read known hosts from /home/jay/.ssh/known_hosts
* SSH host check: 0, key: AAAAB3NzaC1yc2EAAAABIwAAAQEAxClm+tCD0zPg+o50pmqJSkyRTPZoQvbb5y0SsVFDGArkukON2EPqs+0Y7rrs03CJ/AcYC/rYN7ymoUfIyEtxIiUFeOTQkprin2Db99eczp9pQK91PaqmlhHnfySKfxIEi46mq3jqLvgM5PbRZ9VlBY7Kbg+hPyIPgl1mC+jS5c3MKbIy/eMrCc5oAap+DuoVqdiTxoT1x8ZCfGnaInTJyW33LWIUvfB2OSpJ+w/g4f/vJnKHkuqOWKmMDK3QcRAjqVluDIit/xlIMj/9bRD5vdiTkqpqWTe5ecae4zgs+wMtiJYjD3vgAtyeobNJ5zUlNxts/b4n/thG1MlPlc3rGw==
* SSH authentication methods available: publickey,password
* Using ssh public key file /home/jay/.ssh/id_dsa.pub
* Using ssh private key file /home/jay/.ssh/id_dsa
  0 0 0 0 0 0 0 0 --:--:-- 0:00:02 --:--:-- 0* SSH public key authentication failed: Username/PublicKey combination invalid
* Initialized password authentication
* Authentication complete
* File already completely downloaded
  0 0 0 0 0 0 0 0 --:--:-- 0:00:02 --:--:-- 0
  0 0 0 0 0 0 0 0 --:--:-- 0:00:02 --:--:-- 0* Connection #0 to host vtd left intact

* Closing connection #0

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Received on 2011-05-23