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[thirdparty/man-pages.git] / man3 / posix_fallocate.3

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.TH POSIX_FALLOCATE 3  2015-03-02 "GNU" "Linux Programmer's Manual"
.SH NAME
posix_fallocate \- allocate file space
.SH SYNOPSIS
.nf
.B #include <fcntl.h>
.sp
.BI "int posix_fallocate(int " fd ", off_t " offset ", off_t " len );
.fi
.sp
.ad l
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.sp
.BR posix_fallocate ():
.RS 4
_XOPEN_SOURCE\ >=\ 600 || _POSIX_C_SOURCE\ >=\ 200112L
.RE
.ad
.SH DESCRIPTION
The function
.BR posix_fallocate ()
ensures that disk space is allocated for the file referred to by the
descriptor
.I fd
for the bytes in the range starting at
.I offset
and continuing for
.I len
bytes.
After a successful call to
.BR posix_fallocate (),
subsequent writes to bytes in the specified range are
guaranteed not to fail because of lack of disk space.

If the size of the file is less than
.IR offset + len ,
then the file is increased to this size;
otherwise the file size is left unchanged.
.SH RETURN VALUE
.BR posix_fallocate ()
returns zero on success, or an error number on failure.
Note that
.I errno
is not set.
.SH ERRORS
.TP
.B EBADF
.I fd
is not a valid file descriptor, or is not opened for writing.
.TP
.B EFBIG
.I offset+len
exceeds the maximum file size.
.TP
.B EINVAL
.I offset
was less than 0, or
.I len
was less than or equal to 0.
.TP
.B ENODEV
.I fd
does not refer to a regular file.
.TP
.B ENOSPC
There is not enough space left on the device containing the file
referred to by
.IR fd .
.TP
.B ESPIPE
.I fd
refers to a pipe.
.SH VERSIONS
.BR posix_fallocate ()
is available since glibc 2.1.94.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lb lb lb
l l l.
Interface	Attribute	Value
T{
.BR posix_fallocate ()
T}	Thread safety	MT-Safe
.TE
.SH CONFORMING TO
POSIX.1-2001.