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Diffstat (limited to 'static/plan9-4e/man2/iounit.2')
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diff --git a/static/plan9-4e/man2/iounit.2 b/static/plan9-4e/man2/iounit.2 new file mode 100644 index 00000000..a31d7079 --- /dev/null +++ b/static/plan9-4e/man2/iounit.2 @@ -0,0 +1,37 @@ +.TH IOUNIT 2 +.SH NAME +iounit \- return size of atomic I/O unit for file descriptor +.SH SYNOPSIS +.B #include <u.h> +.br +.B #include <libc.h> +.PP +.B +int iounit(int fd) +.SH DESCRIPTION +Reads and writes of files are transmitted using the 9P protocol (see +.IR intro (5)) +and in general, operations involving large amounts of data must be +broken into smaller pieces by the operating system. +The `I/O unit' associated with each file descriptor records the maximum +size, in bytes, that may be read or written without breaking up the transfer. +.PP +The +.I iounit +routine uses the +.IR dup (3) +interface to discover the I/O unit size for the file descriptor +.I fd +and returns its value. +Certain file descriptors, particularly those associated with devices, may +have no specific I/O unit, in which case +.I iounit +will return +.BR 0 . +.SH SOURCE +.B /sys/src/libc/9sys +.SH SEE ALSO +.IR dup (3), +.IR read (5) +.SH DIAGNOSTICS +Returns zero if any error occurs or if the I/O unit size of the fd is unspecified or unknown. |