1 .\" Copyright (C) 1999 Joseph Samuel Myers.
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4 .\" manual provided the copyright notice and this permission notice are
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7 .\" Permission is granted to copy and distribute modified versions of this
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13 .\" manual page may be incorrect or out-of-date. The author(s) assume no
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17 .\" which is licensed free of charge, as they might when working
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23 .TH PREAD 2 2010-09-26 "Linux" "Linux Programmer's Manual"
25 pread, pwrite \- read from or write to a file descriptor at a given offset
27 .B #include <unistd.h>
29 .BI "ssize_t pread(int " fd ", void *" buf ", size_t " count \
32 .BI "ssize_t pwrite(int " fd ", const void *" buf ", size_t " count \
36 Feature Test Macro Requirements for glibc (see
37 .BR feature_test_macros (7)):
45 _XOPEN_SOURCE\ >=\ 500
47 || /* Since glibc 2.12: */ _POSIX_C_SOURCE\ >=\ 200809L
55 bytes from file descriptor
59 (from the start of the file) into the buffer starting at
61 The file offset is not changed.
66 bytes from the buffer starting at
68 to the file descriptor
72 The file offset is not changed.
74 The file referenced by
76 must be capable of seeking.
78 On success, the number of bytes read or written is returned (zero
79 indicates that nothing was written, in the case of
82 end of file, in the case of
84 or \-1 on error, in which case
86 is set to indicate the error.
91 to any error specified for
98 to any error specified for
107 system calls were added to Linux in
108 version 2.1.60; the entries in the i386 system call table were added
110 C library support (including emulation using
112 on older kernels without the system calls) was added in glibc 2.1.