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@(#)truncate.2 6.1 (Berkeley) 05/15/85

C 5 truncate - truncate a file to a specified length

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

ftruncate(fd, length)
int fd, length;

Truncate causes the file named by path or referenced by fd to be truncated 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. Truncate succeeds unless:

15 [EPERM] The pathname contains a character with the high-order bit set.

15 [ENOENT] The pathname was too long.

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

15 [ENOENT] The named file does not exist.

15 [EACCES] A component of the path prefix denies search permission.

15 [EISDIR] The named file is a directory.

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

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

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

Ftruncate succeeds unless:

15 [EBADF] The fd is not a valid descriptor.

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

open(2) Partial blocks discarded as the result of truncation are not zero filled; this can result in holes in files which do not read as zero.

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