/share/man/man4/fd.4

https://bitbucket.org/freebsd/freebsd-head/ · Forth · 105 lines · 105 code · 0 blank · 0 comment · 2 complexity · 6dab5cb82d253f151918dc9846f5aac8 MD5 · raw file 

    

  1. .\" Copyright (c) 1990, 1991, 1993
    2. 

  2. .\"	The Regents of the University of California.  All rights reserved.
    3. 

  3. .\"
    4. 

  4. .\" Redistribution and use in source and binary forms, with or without
    5. 

  5. .\" modification, are permitted provided that the following conditions
    6. 

  6. .\" are met:
    7. 

  7. .\" 1. Redistributions of source code must retain the above copyright
    8. 

  8. .\"    notice, this list of conditions and the following disclaimer.
    9. 

  9. .\" 2. Redistributions in binary form must reproduce the above copyright
    10. 

  10. .\"    notice, this list of conditions and the following disclaimer in the
    11. 

  11. .\"    documentation and/or other materials provided with the distribution.
    12. 

  12. .\" 3. All advertising materials mentioning features or use of this software
    13. 

  13. .\"    must display the following acknowledgement:
    14. 

  14. .\"	This product includes software developed by the University of
    15. 

  15. .\"	California, Berkeley and its contributors.
    16. 

  16. .\" 4. Neither the name of the University nor the names of its contributors
    17. 

  17. .\"    may be used to endorse or promote products derived from this software
    18. 

  18. .\"    without specific prior written permission.
    19. 

  19. .\"
    20. 

  20. .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
    21. 

  21. .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
    22. 

  22. .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
    23. 

  23. .\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
    24. 

  24. .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
    25. 

  25. .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
    26. 

  26. .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
    27. 

  27. .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
    28. 

  28. .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
    29. 

  29. .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
    30. 

  30. .\" SUCH DAMAGE.
    31. 

  31. .\"
    32. 

  32. .\"     @(#)fd.4	8.1 (Berkeley) 6/9/93
    33. 

  33. .\" $FreeBSD$
    34. 

  34. .\"
    35. 

  35. .Dd June 9, 1993
    36. 

  36. .Dt FD 4
    37. 

  37. .Os
    38. 

  38. .Sh NAME
    39. 

  39. .Nm fd ,
    40. 

  40. .Nm stdin ,
    41. 

  41. .Nm stdout ,
    42. 

  42. .Nm stderr
    43. 

  43. .Nd file descriptor files
    44. 

  44. .Sh DESCRIPTION
    45. 

  45. The files
    46. 

  46. .Pa /dev/fd/0
    47. 

  47. through
    48. 

  48. .Pa /dev/fd/#
    49. 

  49. refer to file descriptors which can be accessed through the file
    50. 

  50. system.
    51. 

  51. If the file descriptor is open and the mode the file is being opened
    52. 

  52. with is a subset of the mode of the existing descriptor, the call:
    53. 

  53. .Bd -literal -offset indent
    54. 

  54. fd = open("/dev/fd/0", mode);
    55. 

  55. .Ed
    56. 

  56. .Pp
    57. 

  57. and the call:
    58. 

  58. .Bd -literal -offset indent
    59. 

  59. fd = fcntl(0, F_DUPFD, 0);
    60. 

  60. .Ed
    61. 

  61. .Pp
    62. 

  62. are equivalent.
    63. 

  63. .Pp
    64. 

  64. Opening the files
    65. 

  65. .Pa /dev/stdin ,
    66. 

  66. .Pa /dev/stdout
    67. 

  67. and
    68. 

  68. .Pa /dev/stderr
    69. 

  69. is equivalent to the following calls:
    70. 

  70. .Bd -literal -offset indent
    71. 

  71. fd = fcntl(STDIN_FILENO,  F_DUPFD, 0);
    72. 

  72. fd = fcntl(STDOUT_FILENO, F_DUPFD, 0);
    73. 

  73. fd = fcntl(STDERR_FILENO, F_DUPFD, 0);
    74. 

  74. .Ed
    75. 

  75. .Pp
    76. 

  76. Flags to the
    77. 

  77. .Xr open 2
    78. 

  78. call other than
    79. 

  79. .Dv O_RDONLY ,
    80. 

  80. .Dv O_WRONLY
    81. 

  81. and
    82. 

  82. .Dv O_RDWR
    83. 

  83. are ignored.
    84. 

  84. .Sh IMPLEMENTATION NOTES
    85. 

  85. By default,
    86. 

  86. .Pa /dev/fd
    87. 

  87. is provided by
    88. 

  88. .Xr devfs 5 ,
    89. 

  89. which provides nodes for the first three file descriptors.
    90. 

  90. Some sites may require nodes for additional file descriptors; these can be
    91. 

  91. made available by mounting
    92. 

  92. .Xr fdescfs 5
    93. 

  93. on
    94. 

  94. .Pa /dev/fd .
    95. 

  95. .Sh FILES
    96. 

  96. .Bl -tag -width /dev/stderr -compact
    97. 

  97. .It Pa /dev/fd/#
    98. 

  98. .It Pa /dev/stdin
    99. 

  99. .It Pa /dev/stdout
    100. 

  100. .It Pa /dev/stderr
    101. 

  101. .El
    102. 

  102. .Sh SEE ALSO
    103. 

  103. .Xr tty 4 ,
    104. 

  104. .Xr devfs 5 ,
    105. 

  105. .Xr fdescfs 5
    106.