bsd/man/man2/truncate.2

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  34 .\"     @(#)truncate.2  8.1 (Berkeley) 6/4/93
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  36 .Dd June 4, 1993
  37 .Dt TRUNCATE 2
  38 .Os BSD 4.2
  39 .Sh NAME
  40 .Nm truncate ,
  41 .Nm ftruncate
  42 .Nd truncate or extend a file to a specified length
  43 .Sh SYNOPSIS
  44 .Fd #include <unistd.h>
  45 .Ft int
  46 .Fn truncate "const char *path" "off_t length"
  47 .Ft int
  48 .Fn ftruncate "int fd" "off_t length"
  49 .Sh DESCRIPTION
  50 .Fn Truncate
  51 causes the file named by
  52 .Fa path
  53 or referenced by
  54 .Fa fd
  55 to be truncated or extended to
  56 .Fa length
  57 bytes in size.  If the file previously
  58 was larger than this size, the extra data
  59 is lost. If the file was smaller than this size, it will be extended as
  60 if by writing bytes with the value zero.
  61 With
  62 .Fn ftruncate ,
  63 the file must be open for writing.
  64 .Sh RETURN VALUES
  65 A value of 0 is returned if the call succeeds.  If the call
  66 fails a -1 is returned, and the global variable
  67 .Va errno
  68 specifies the error.
  69 .Sh ERRORS
  70 .Fn Truncate
  71 succeeds unless:
  72 .Bl -tag -width Er
  73 .It Bq Er ENOTDIR
  74 A component of the path prefix is not a directory.
  75 .It Bq Er ENAMETOOLONG
  76 A component of a pathname exceeded
  77 .Dv {NAME_MAX}
  78 characters, or an entire path name exceeded
  79 .Dv {PATH_MAX}
  80 characters.
  81 .It Bq Er ENOENT
  82 The named file does not exist.
  83 .It Bq Er EACCES
  84 Search permission is denied for a component of the path prefix.
  85 .It Bq Er EACCES
  86 The named file is not writable by the user.
  87 .It Bq Er ELOOP
  88 Too many symbolic links were encountered in translating the pathname.
  89 .It Bq Er EISDIR
  90 The named file is a directory.
  91 .It Bq Er EROFS
  92 The named file resides on a read-only file system.
  93 .It Bq Er ETXTBSY
  94 The file is a pure procedure (shared text) file that is being executed.
  95 .It Bq Er EIO
  96 An I/O error occurred updating the inode.
  97 .It Bq Er EFAULT
  98 .Fa Path
  99 points outside the process's allocated address space.
 100 .El
 101 .Pp
 102 .Fn Ftruncate
 103 succeeds unless:
 104 .Bl -tag -width Er
 105 .It Bq Er EBADF
 106 The
 107 .Fa fd
 108 is not a valid descriptor.
 109 .It Bq Er EINVAL
 110 The
 111 .Fa fd
 112 references a socket, not a file.
 113 .It Bq Er EINVAL
 114 The
 115 .Fa fd
 116 is not open for writing.
 117 .El
 118 .Sh SEE ALSO
 119 .Xr open 2
 120 .Sh BUGS
 121 These calls should be generalized to allow ranges
 122 of bytes in a file to be discarded.
 123 .Pp
 124 Use of
 125 .Fn truncate
 126 to extend a file is not portable.
 127 .Sh HISTORY
 128 The
 129 .Fn truncate
 130 and
 131 .Fn ftruncate
 132 function calls appeared in
 133 .Bx 4.2 .