1TRUNCATE(3P)               POSIX Programmer's Manual              TRUNCATE(3P)
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PROLOG

6       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
7       implementation of this interface may differ (consult the  corresponding
8       Linux  manual page for details of Linux behavior), or the interface may
9       not be implemented on Linux.
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NAME

12       truncate - truncate a file to a specified length
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SYNOPSIS

15       #include <unistd.h>
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17       int truncate(const char *path, off_t length);
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DESCRIPTION

21       The truncate() function shall cause the regular file named by  path  to
22       have a size which shall be equal to length bytes.
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24       If  the  file previously was larger than length, the extra data is dis‐
25       carded. If the file was previously shorter than  length,  its  size  is
26       increased, and the extended area appears as if it were zero-filled.
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28       The  application shall ensure that the process has write permission for
29       the file.
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31       If the request would cause the file size to exceed the soft  file  size
32       limit  for  the  process, the request shall fail and the implementation
33       shall generate the SIGXFSZ signal for the process.
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35       This function shall not modify  the  file  offset  for  any  open  file
36       descriptions  associated  with the file. Upon successful completion, if
37       the file size is changed, this  function  shall  mark  for  update  the
38       st_ctime  and  st_mtime fields of the file, and the S_ISUID and S_ISGID
39       bits of the file mode may be cleared.
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RETURN VALUE

42       Upon successful completion, truncate() shall return  0.  Otherwise,  -1
43       shall be returned, and errno set to indicate the error.
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ERRORS

46       The truncate() function shall fail if:
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48       EINTR  A signal was caught during execution.
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50       EINVAL The length argument was less than 0.
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52       EFBIG or EINVAL
53              The length argument was greater than the maximum file size.
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55       EIO    An  I/O  error  occurred while reading from or writing to a file
56              system.
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58       EACCES A component of the path  prefix  denies  search  permission,  or
59              write permission is denied on the file.
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61       EISDIR The named file is a directory.
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63       ELOOP  A loop exists in symbolic links encountered during resolution of
64              the path argument.
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66       ENAMETOOLONG
67              The length of the path argument exceeds {PATH_MAX} or a pathname
68              component is longer than {NAME_MAX}.
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70       ENOENT A component of path does not name an existing file or path is an
71              empty string.
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73       ENOTDIR
74              A component of the path prefix of path is not a directory.
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76       EROFS  The named file resides on a read-only file system.
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79       The truncate() function may fail if:
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81       ELOOP  More than {SYMLOOP_MAX} symbolic links were  encountered  during
82              resolution of the path argument.
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84       ENAMETOOLONG
85              Pathname  resolution of a symbolic link produced an intermediate
86              result whose length exceeds {PATH_MAX}.
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89       The following sections are informative.
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EXAMPLES

92       None.
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APPLICATION USAGE

95       None.
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RATIONALE

98       None.
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FUTURE DIRECTIONS

101       None.
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SEE ALSO

104       open(), the Base Definitions volume of IEEE Std 1003.1-2001, <unistd.h>
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107       Portions of this text are reprinted and reproduced in  electronic  form
108       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
109       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
110       Specifications  Issue  6,  Copyright  (C) 2001-2003 by the Institute of
111       Electrical and Electronics Engineers, Inc and The Open  Group.  In  the
112       event of any discrepancy between this version and the original IEEE and
113       The Open Group Standard, the original IEEE and The Open Group  Standard
114       is  the  referee document. The original Standard can be obtained online
115       at http://www.opengroup.org/unix/online.html .
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119IEEE/The Open Group                  2003                         TRUNCATE(3P)
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