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setbuf.3p (3021B)

    

  1. '\" et
  2. .TH SETBUF "3P" 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. setbuf
  12. \(em assign buffering to a stream
  13. .SH SYNOPSIS
  14. .LP
  15. .nf
  16. #include <stdio.h>
  17. .P
  18. void setbuf(FILE *restrict \fIstream\fP, char *restrict \fIbuf\fP);
  19. .fi
  20. .SH DESCRIPTION
  21. The functionality described on this reference page is aligned with the
  22. ISO\ C standard. Any conflict between the requirements described here and the
  23. ISO\ C standard is unintentional. This volume of POSIX.1\(hy2017 defers to the ISO\ C standard.
  24. .P
  25. Except that it returns no value, the function call:
  26. .sp
  27. .RS 4
  28. .nf
  30. setbuf(stream, buf)
  31. .fi
  32. .P
  33. .RE
  34. .P
  35. shall be equivalent to:
  36. .sp
  37. .RS 4
  38. .nf
  40. setvbuf(stream, buf, _IOFBF, BUFSIZ)
  41. .fi
  42. .P
  43. .RE
  44. .P
  45. if
  46. .IR buf
  47. is not a null pointer, or to:
  48. .sp
  49. .RS 4
  50. .nf
  52. setvbuf(stream, buf, _IONBF, BUFSIZ)
  53. .fi
  54. .P
  55. .RE
  56. .P
  57. if
  58. .IR buf
  59. is a null pointer.
  60. .SH "RETURN VALUE"
  61. The
  62. \fIsetbuf\fR()
  63. function shall not return a value.
  64. .SH ERRORS
  65. Although the
  66. \fIsetvbuf\fR()
  67. interface may set
  68. .IR errno
  69. in defined ways, the value of
  70. .IR errno
  71. after a call to
  72. \fIsetbuf\fR()
  73. is unspecified.
  74. .LP
  75. .IR "The following sections are informative."
  76. .SH EXAMPLES
  77. None.
  78. .SH "APPLICATION USAGE"
  79. A common source of error is allocating buffer space as an ``automatic''
  80. variable in a code block, and then failing to close the stream in the
  81. same block.
  82. .P
  83. With
  84. \fIsetbuf\fR(),
  85. allocating a buffer of BUFSIZ bytes does not necessarily imply that all
  86. of BUFSIZ bytes are used for the buffer area.
  87. .P
  88. Since
  89. .IR errno
  90. is not required to be unchanged on success, in order to correctly detect
  91. and possibly recover from errors, applications should use
  92. \fIsetvbuf\fR()
  93. instead of
  94. \fIsetbuf\fR().
  95. .SH RATIONALE
  96. None.
  97. .SH "FUTURE DIRECTIONS"
  98. None.
  99. .SH "SEE ALSO"
  100. .IR "Section 2.5" ", " "Standard I/O Streams",
  101. .IR "\fIfopen\fR\^(\|)",
  102. .IR "\fIsetvbuf\fR\^(\|)"
  103. .P
  104. The Base Definitions volume of POSIX.1\(hy2017,
  105. .IR "\fB<stdio.h>\fP"
  106. .\"
  107. .SH COPYRIGHT
  108. Portions of this text are reprinted and reproduced in electronic form
  109. from IEEE Std 1003.1-2017, Standard for Information Technology
  110. -- Portable Operating System Interface (POSIX), The Open Group Base
  111. Specifications Issue 7, 2018 Edition,
  112. Copyright (C) 2018 by the Institute of
  113. Electrical and Electronics Engineers, Inc and The Open Group.
  114. In the event of any discrepancy between this version and the original IEEE and
  115. The Open Group Standard, the original IEEE and The Open Group Standard
  116. is the referee document. The original Standard can be obtained online at
  117. http://www.opengroup.org/unix/online.html .
  118. .PP
  119. Any typographical or formatting errors that appear
  120. in this page are most likely
  121. to have been introduced during the conversion of the source files to
  122. man page format. To report such errors, see
  123. https://www.kernel.org/doc/man-pages/reporting_bugs.html .