truncate(2) [opendarwin man page]

TRUNCATE(2)						      BSD System Calls Manual						       TRUNCATE(2)

NAME

     truncate, ftruncate -- truncate or extend a file to a specified length

SYNOPSIS

     #include <unistd.h>

     int
     truncate(const char *path, off_t length);

     int
     ftruncate(int fd, off_t length);

DESCRIPTION

     Truncate() causes the file named by path or referenced by fd to be truncated or extended to length bytes in size.	If the file previously was
     larger than this size, the extra data is lost. If the file was smaller than this size, it will be extended as if by writing bytes with the
     value zero.  With ftruncate(), the file must be open for writing.

RETURN VALUES

     A value of 0 is returned if the call succeeds.  If the call fails a -1 is returned, and the global variable errno specifies the error.

ERRORS

     Truncate() succeeds unless:

     [ENOTDIR]		A component of the path prefix is not a directory.

     [ENAMETOOLONG]	A component of a pathname exceeded {NAME_MAX} characters, or an entire path name exceeded {PATH_MAX} characters.

     [ENOENT]		The named file does not exist.

     [EACCES]		Search permission is denied for a component of the path prefix.

     [EACCES]		The named file is not writable by the user.

     [ELOOP]		Too many symbolic links were encountered in translating the pathname.

     [EISDIR]		The named file is a directory.

     [EROFS]		The named file resides on a read-only file system.

     [ETXTBSY]		The file is a pure procedure (shared text) file that is being executed.

     [EIO]		An I/O error occurred updating the inode.

     [EFAULT]		Path points outside the process's allocated address space.

     Ftruncate() succeeds unless:

     [EBADF]		The fd is not a valid descriptor.

     [EINVAL]		The fd references a socket, not a file.

     [EINVAL]		The fd is not open for writing.

SEE ALSO

     open(2)

BUGS

     These calls should be generalized to allow ranges of bytes in a file to be discarded.

     Use of truncate() to extend a file is not portable.

HISTORY

     The truncate() and ftruncate() function calls appeared in 4.2BSD.

4.2 Berkeley Distribution					   June 4, 1993 					 4.2 Berkeley Distribution

TRUNCATE(2)						      BSD System Calls Manual						       TRUNCATE(2)

NAME

     ftruncate, truncate -- truncate or extend a file to a specified length

SYNOPSIS

     #include <unistd.h>

     int
     ftruncate(int fildes, off_t length);

     int
     truncate(const char *path, off_t length);

DESCRIPTION

     ftruncate() and truncate() cause the file named by path, or referenced by fildes, to be truncated (or extended) to length bytes in size. If
     the file size exceeds length, any extra data is discarded. If the file size is smaller than length, the file is extended and filled with
     zeros to the indicated length.  The ftruncate() form requires the file to be open for writing.

     Note: ftruncate() and truncate() do not modify the current file offset for any open file descriptions associated with the file.

RETURN VALUES

     A value of 0 is returned if the call succeeds.  If the call fails a -1 is returned, and the global variable errno specifies the error.

ERRORS

     The ftruncate() system call will fail if:

     [EBADF]		fildes is not a valid descriptor open for writing.

     [EFBIG]		The file is a regular file and length is greater than the offset maximum established in the open file description associ-
			ated with fildes.

     [EINVAL]		fildes references a socket, not a file.

     [EINVAL]		fildes is not open for writing.

     [EROFS]		The named file resides on a read-only file system.

     The truncate() system call will fail if:

     [EACCES]		Search permission is denied for a component of the path prefix.

     [EACCES]		The named file is not writable by the user.

     [EFAULT]		Path points outside the process's allocated address space.

     [EISDIR]		The named file is a directory.

     [ELOOP]		Too many symbolic links are encountered in translating the pathname.  This is taken to be indicative of a looping symbolic
			link.

     [ENAMETOOLONG]	A component of a pathname exceeds {NAME_MAX} characters, or an entire path name exceeds {PATH_MAX} characters.

     [ENOENT]		The named file does not exist.

     [ENOTDIR]		A component of the path prefix is not a directory.

     [EROFS]		The named file resides on a read-only file system.

     [ETXTBSY]		The file is a pure procedure (shared text) file that is being executed.

     The ftruncate() and truncate() system calls will fail if:

     [EFBIG]		The length argument was greater than the maximum file size.

     [EINTR]		A signal is caught during execution.

     [EINVAL]		The length argument is less than 0.

     [EIO]		An I/O error occurred while reading from or writing to a file system.

SEE ALSO

     open(2)

BUGS

     These calls should be generalized to allow ranges of bytes in a file to be discarded.

     Use of truncate() to extend a file is not portable.

HISTORY

     The truncate() and ftruncate() function calls appeared in 4.2BSD.

4.2 Berkeley Distribution					   June 4, 1993 					 4.2 Berkeley Distribution