truncate(3C) (C Programming Language Utilities) truncate(3C)
NAME
truncate, ftruncate - set a file to a specified length
SYNOPSIS
#include <unistd.h>
int truncate (const char *path, offt length);
int ftruncate (int fildes, offt length);
DESCRIPTION
The file whose name is given by path or referenced by the descriptor
fildes has its size set to length bytes.
If the file was previously longer than length, bytes past length will
no longer be accessible. If it was shorter, bytes from the EOF
before the call to the EOF after the call will be read in as zeros.
The effective user ID of the process must have write permission for
the file, and for ftruncate the file must be open for writing.
truncate fails if one or more of the following are true:
EACCES Search permission is denied on a component of the
path prefix.
EACCES Write permission is denied for the file referred to
by path.
EFAULT path points outside the process's allocated address
space.
EINTR A signal was caught during execution of the
truncate routine.
EINVAL path is not an ordinary file.
EIO An I/O error occurred while reading from or writing
to the file system.
EISDIR The file referred to by path is a directory.
ELOOP Too many symbolic links were encountered in
translating path.
EMFILE The maximum number of file descriptors available to
the process has been reached.
EMULTIHOP Components of path require hopping to multiple
remote machines and file system type does not allow
it.
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truncate(3C) (C Programming Language Utilities) truncate(3C)
ENAMETOOLONG The length of a path component exceeds {NAME_MAX}
characters, or the length of path exceeds
{PATH_MAX} characters.
ENFILE Could not allocate any more space for the system
file table.
ENOENT Either a component of the path prefix or the file
referred to by path does not exist.
ENOLINK path points to a remote machine and the link to
that machine is no longer active.
ENOTDIR A component of the path prefix of path is not a
directory.
EROFS The file referred to by path resides on a read-only
file system.
ETXTBSY The file referred to by path is a pure procedure
(shared text) file that is being executed.
ftruncate fails if one or more of the following are true:
EAGAIN The file exists, mandatory file/record locking is
set, and there are outstanding record locks on the
file [see chmod(2)].
EBADF fildes is not a file descriptor open for writing.
EINTR A signal was caught during execution of the
ftruncate routine.
EIO An I/O error occurred while reading from or writing
to the file system.
ENOLINK fildes points to a remote machine and the link to
that machine is no longer active.
EINVAL fildes does not correspond to an ordinary file.
SEE ALSO
fcntl(2), open(2)
DIAGNOSTICS
Upon successful completion, a value of 0 is returned. Otherwise, a
value of -1 is returned and errno is set to indicate the error.
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