Open System Services System Calls Reference Manual (G06.29+, H06.08+, J06.03+)

System Functions (r) readv(2)
Use From a Threaded Application
The thread-aware readv() function behaves exactly the same as spt_readvz() in the Standard
POSIX Threads library. For file descriptors for regular files, if this thread-aware readv() func-
tion must wait for an I/O operation to complete on an open file, this function blocks the thread
(instead of the entire process) that called it, while it waits for the I/O operation to complete.
This function serializes file operations on an open file. If a thread calls readv() to access a file
that already has a file operation in progress by a different thread, this thread is blocked until the
prior file operation is complete.
NOTES
To use the readv() functionality in a threaded application that uses the Standard POSIX Threads
library, see spt_readvz(2).
To use this function in a threaded application that uses the POSIX User Thread Model library on
systems running H06.21 or later RVUs or J06.10 or later RVUs, you must perform all of the fol-
lowing tasks to make the function thread-aware in a multi-threaded application:
• Compile the application using the _PUT_MODEL_ feature test macro or equivalent
compiler command option.
• Link the application to the zputdll library (/G/system/zdllnnn/zputdll).
On systems running H06.24 or later H-series RVUs or J06.13 or later J-series RVUs, you can use
this function with 32-bit or 64-bit OSS applications.
To use this function in a 32-bit threaded application on systems running H06.24 or later RVUs or
J06.13 or later RVUs, perform the same tasks (described above) used to make the function
thread-aware in a multi-threaded application on systems running H06.21/J06.10 or later RVUs.
To use this function in a 64-bit threaded application on systems running H06.24 or later RVUs or
J06.13 or later RVUs, you must perform all of the following tasks to make the function thread-
aware in a multi-threaded application:
• Compile the application using the _PUT_MODEL_ feature test macro or equivalent
compiler command option.
• Compile the application using the -Wlp64 compiler command option.
• Link the application to the yputdll library (/G/system/zdllnnn/yputdll).
For detailed information about writing multi-threaded and 64-bit applications for the Open Sys-
tem Services environment, see the Open System Services Programmer’s Guide.
RETURN VALUES
Upon successful completion, the readv() function returns the number of bytes actually read and
placed into the buffers. The function guarantees to read the number of bytes requested only if the
descriptor references a regular file that has at least that number of bytes left before EOF.
If the read otherwise fails, the value -1 is returned, errno is set to indicate the error, and the con-
tents of the buffers are indeterminate.
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