Bug 97491 - sendfile man page should mention short "sends"
Summary: sendfile man page should mention short "sends"
Status: RESOLVED CODE_FIX
Alias: None
Product: Documentation
Classification: Unclassified
Component: man-pages (show other bugs)
Hardware: All Linux
: P1 normal
Assignee: documentation_man-pages@kernel-bugs.osdl.org
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2015-04-29 08:09 UTC by Gregor Jasny
Modified: 2015-05-05 10:00 UTC (History)
1 user (show)

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Regression: No
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Description Gregor Jasny 2015-04-29 08:09:38 UTC 
Hello,

Linux 3.16 (3.16.0-4-amd64 #1 SMP Debian 3.16.7-ckt4-1, glibc 2.19-18) seems to truncate larger requests to 2G (file to file copy):

strace output:
  sendfile(4, 3, [0], 10240000000)        = 2147479552


I know one should expect this behavior from read/write calls but for sendfile it was somehow unexpected.

Maybe you could mention that fact in the man page for sendfile?

Thanks,
Gregor
Comment 1 Michael Kerrisk 2015-05-05 10:00:58 UTC 
I added some text to cover this:

RETURN VALUE
       If the transfer was successful, the number of bytes writ‐
       ten  to  out_fd is returned.  Note that a successful call
       to sendfile() may write fewer bytes than  requested;  the
       caller should be prepared to retry the call if there were
       unsent bytes.

Hopefully that suffices?

Thanks,

Michael
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