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sys_uio.h.0p (2925B)

    

  1. '\" et
  2. .TH sys_uio.h "0P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
  3. .\"
  4. .SH PROLOG
  5. This manual page is part of the POSIX Programmer's Manual.
  6. The Linux implementation of this interface may differ (consult
  7. the corresponding Linux manual page for details of Linux behavior),
  8. or the interface may not be implemented on Linux.
  9. .\"
  10. .SH NAME
  11. sys/uio.h
  12. \(em definitions for vector I/O operations
  13. .SH SYNOPSIS
  14. .LP
  15. .nf
  16. #include <sys/uio.h>
  17. .fi
  18. .SH DESCRIPTION
  19. The
  20. .IR <sys/uio.h> 
  21. header shall define the
  22. .BR iovec
  23. structure, which shall include at least the following members:
  24. .sp
  25. .RS 4
  26. .nf
  28. void   *iov_base  \fRBase address of a memory region for input or output.\fR
  29. size_t  iov_len   \fRThe size of the memory pointed to by \fIiov_base.\fR
  30. .fi
  31. .P
  32. .RE
  33. .P
  34. The
  35. .IR <sys/uio.h> 
  36. header uses the
  37. .BR iovec
  38. structure for scatter/gather I/O.
  39. .P
  40. The
  41. .IR <sys/uio.h> 
  42. header shall define the
  43. .BR ssize_t
  44. and
  45. .BR size_t
  46. types as described in
  47. .IR <sys/types.h> .
  48. .P
  49. The following shall be declared as functions and may also be defined
  50. as macros. Function prototypes shall be provided.
  51. .sp
  52. .RS 4
  53. .nf
  55. ssize_t readv(int, const struct iovec *, int);
  56. ssize_t writev(int, const struct iovec *, int);
  57. .fi
  58. .P
  59. .RE
  60. .LP
  61. .IR "The following sections are informative."
  62. .SH "APPLICATION USAGE"
  63. The implementation can put a limit on the number of scatter/gather
  64. elements which can be processed in one call. The symbol
  65. {IOV_MAX}
  66. defined in
  67. .IR <limits.h> 
  68. should always be used to learn about the limits instead of assuming a
  69. fixed value.
  70. .SH RATIONALE
  71. Traditionally, the maximum number of scatter/gather elements the system
  72. can process in one call were described by the symbolic value
  73. {UIO_MAXIOV}.
  74. In IEEE\ Std\ 1003.1\(hy2001 this value is replaced by the constant
  75. {IOV_MAX}
  76. which can be found in
  77. .IR <limits.h> .
  78. .SH "FUTURE DIRECTIONS"
  79. None.
  80. .SH "SEE ALSO"
  81. .IR "\fB<limits.h>\fP",
  82. .IR "\fB<sys_types.h>\fP"
  83. .P
  84. The System Interfaces volume of POSIX.1\(hy2017,
  85. .IR "\fIread\fR\^(\|)",
  86. .IR "\fIreadv\fR\^(\|)",
  87. .IR "\fIwrite\fR\^(\|)",
  88. .IR "\fIwritev\fR\^(\|)"
  89. .\"
  90. .SH COPYRIGHT
  91. Portions of this text are reprinted and reproduced in electronic form
  92. from IEEE Std 1003.1-2017, Standard for Information Technology
  93. -- Portable Operating System Interface (POSIX), The Open Group Base
  94. Specifications Issue 7, 2018 Edition,
  95. Copyright (C) 2018 by the Institute of
  96. Electrical and Electronics Engineers, Inc and The Open Group.
  97. In the event of any discrepancy between this version and the original IEEE and
  98. The Open Group Standard, the original IEEE and The Open Group Standard
  99. is the referee document. The original Standard can be obtained online at
  100. http://www.opengroup.org/unix/online.html .
  101. .PP
  102. Any typographical or formatting errors that appear
  103. in this page are most likely
  104. to have been introduced during the conversion of the source files to
  105. man page format. To report such errors, see
  106. https://www.kernel.org/doc/man-pages/reporting_bugs.html .