1TRUNCATE(2)                Linux Programmer's Manual               TRUNCATE(2)
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NAME

6       truncate, ftruncate - truncate a file to a specified length
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SYNOPSIS

9       #include <unistd.h>
10       #include <sys/types.h>
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12       int truncate(const char *path, off_t length);
13       int ftruncate(int fd, off_t length);
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15   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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17       truncate():
18           _XOPEN_SOURCE >= 500
19               || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L
20               || /* Glibc versions <= 2.19: */ _BSD_SOURCE
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22       ftruncate():
23           _XOPEN_SOURCE >= 500
24               || /* Since glibc 2.3.5: */ _POSIX_C_SOURCE >= 200112L
25               || /* Glibc versions <= 2.19: */ _BSD_SOURCE
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DESCRIPTION

28       The  truncate()  and ftruncate() functions cause the regular file named
29       by path or referenced by fd to be truncated  to  a  size  of  precisely
30       length bytes.
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32       If  the  file  previously  was larger than this size, the extra data is
33       lost.  If the file previously was shorter,  it  is  extended,  and  the
34       extended part reads as null bytes ('\0').
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36       The file offset is not changed.
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38       If  the  size  changed,  then the st_ctime and st_mtime fields (respec‐
39       tively, time of last status change and time of last  modification;  see
40       inode(7))  for the file are updated, and the set-user-ID and set-group-
41       ID mode bits may be cleared.
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43       With ftruncate(), the file must be open for writing;  with  truncate(),
44       the file must be writable.
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RETURN VALUE

47       On  success,  zero is returned.  On error, -1 is returned, and errno is
48       set appropriately.
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ERRORS

51       For truncate():
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53       EACCES Search permission is denied for a component of the path  prefix,
54              or  the  named  file  is  not  writable  by the user.  (See also
55              path_resolution(7).)
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57       EFAULT The argument path points outside the process's allocated address
58              space.
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60       EFBIG  The argument length is larger than the maximum file size. (XSI)
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62       EINTR  While blocked waiting to complete, the call was interrupted by a
63              signal handler; see fcntl(2) and signal(7).
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65       EINVAL The argument length is negative or larger than the maximum  file
66              size.
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68       EIO    An I/O error occurred updating the inode.
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70       EISDIR The named file is a directory.
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72       ELOOP  Too  many  symbolic  links  were  encountered in translating the
73              pathname.
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75       ENAMETOOLONG
76              A component of a pathname exceeded 255 characters, or an  entire
77              pathname exceeded 1023 characters.
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79       ENOENT The named file does not exist.
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81       ENO