TRUNCATE(2) BSD System Calls Manual TRUNCATE(2)NAME
truncate, ftruncate — truncate a file to a specified length
truncate(const char *path, off_t length);
ftruncate(int fd, off_t length);
DESCRIPTIONTruncate() causes the file named by path or referenced by fd to be trun‐
cated to at most length bytes in size. If the file previously was larger
than this size, the extra data is lost. With ftruncate(), the file must
be open for writing.
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.
ERRORSTruncate() succeeds unless:
[ENOTDIR] A component of the path prefix is not a directory.
[EINVAL] The pathname contains a character with the high-order bit set.
A component of a pathname exceeded 255 characters, or an
entire path name exceeded 1023 characters.
[ENOENT] The named file does not exist.
[EACCES] Search permission is denied for a component of the path pre‐
[EACCES] The named file is not writable by the user.
[ELOOP] Too many symbolic links were encountered in translating the
[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
[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.
These calls should be generalized to allow ranges of bytes in a file to
The truncate function call appeared in 4.2BSD.
4.2 Berkeley Distribution June 4, 1993 4.2 Berkeley Distribution