/usr.bin/truncate/truncate.1

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  1. .\"
  2. .\" Copyright (c) 2000 Sheldon Hearn <sheldonh@FreeBSD.org>.
  3. .\" All rights reserved.
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  5. .\" Redistribution and use in source and binary forms, with or without
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  14. .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  15. .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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  26. .\" $FreeBSD$
  27. .\"
  28. .Dd December 19, 2006
  29. .Dt TRUNCATE 1
  30. .Os
  31. .Sh NAME
  32. .Nm truncate
  33. .Nd truncate or extend the length of files
  34. .Sh SYNOPSIS
  35. .Nm
  36. .Op Fl c
  37. .Bk -words
  38. .Fl s Xo
  39. .Sm off
  40. .Op Cm + | -
  41. .Ar size
  42. .Op Cm K | k | M | m | G | g | T | t
  43. .Sm on
  44. .Xc
  45. .Ek
  46. .Ar
  47. .Nm
  48. .Op Fl c
  49. .Bk -words
  50. .Fl r Ar rfile
  51. .Ek
  52. .Ar
  53. .Sh DESCRIPTION
  54. The
  55. .Nm
  56. utility adjusts the length of each regular file given on the command-line.
  57. .Pp
  58. The following options are available:
  59. .Bl -tag -width indent
  60. .It Fl c
  61. Do not create files if they do not exist.
  62. The
  63. .Nm
  64. utility does not treat this as an error.
  65. No error messages are displayed
  66. and the exit value is not affected.
  67. .It Fl r Ar rfile
  68. Truncate or extend files to the length of the file
  69. .Ar rfile .
  70. .It Fl s Xo
  71. .Sm off
  72. .Op Cm + | -
  73. .Ar size
  74. .Op Cm K | k | M | m | G | g | T | t
  75. .Sm on
  76. .Xc
  77. If the
  78. .Ar size
  79. argument is preceded by a plus sign
  80. .Pq Cm + ,
  81. files will be extended by this number of bytes.
  82. If the
  83. .Ar size
  84. argument is preceded by a dash
  85. .Pq Cm - ,
  86. file lengths will be reduced by no more than this number of bytes,
  87. to a minimum length of zero bytes.
  88. Otherwise, the
  89. .Ar size
  90. argument specifies an absolute length to which all files
  91. should be extended or reduced as appropriate.
  92. .Pp
  93. The
  94. .Ar size
  95. argument may be suffixed with one of
  96. .Cm K ,
  97. .Cm M ,
  98. .Cm G
  99. or
  100. .Cm T
  101. (either upper or lower case) to indicate a multiple of
  102. Kilobytes, Megabytes, Gigabytes or Terabytes
  103. respectively.
  104. .El
  105. .Pp
  106. Exactly one of the
  107. .Fl r
  108. and
  109. .Fl s
  110. options must be specified.
  111. .Pp
  112. If a file is made smaller, its extra data is lost.
  113. If a file is made larger,
  114. it will be extended as if by writing bytes with the value zero.
  115. If the file does not exist,
  116. it is created unless the
  117. .Fl c
  118. option is specified.
  119. .Pp
  120. Note that,
  121. while truncating a file causes space on disk to be freed,
  122. extending a file does not cause space to be allocated.
  123. To extend a file and actually allocate the space,
  124. it is necessary to explicitly write data to it,
  125. using (for example) the shell's
  126. .Ql >>
  127. redirection syntax, or
  128. .Xr dd 1 .
  129. .Sh EXIT STATUS
  130. .Ex -std
  131. If the operation fails for an argument,
  132. .Nm
  133. will issue a diagnostic
  134. and continue processing the remaining arguments.
  135. .Sh SEE ALSO
  136. .Xr dd 1 ,
  137. .Xr touch 1 ,
  138. .Xr truncate 2
  139. .Sh STANDARDS
  140. The
  141. .Nm
  142. utility conforms to no known standards.
  143. .Sh HISTORY
  144. The
  145. .Nm
  146. utility first appeared in
  147. .Fx 4.2 .
  148. .Sh AUTHORS
  149. The
  150. .Nm
  151. utility was written by
  152. .An Sheldon Hearn
  153. .Aq sheldonh@starjuice.net .