NAME

truncate, ftruncate − truncate a file to a specified length

SYNOPSIS

truncate(path, length)
char ∗path;
unsigned long length;

ftruncate(fd, length)
int fd;
unsigned long length;

DESCRIPTION

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.

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:

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

[ENAMETOOLONG]
The pathname was too long.

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

[ENOENT] The named file does not exist. 

[EACCES] Either search permission is denied by a component of the path or the file exists, but is unwritable. 

[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. 

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

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

Ftruncate succeeds unless:

[EBADF] The fd is not a valid descriptor of a file open for writing. 

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

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

SEE ALSO

open(2)

BUGS

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. 

Sun Release 3.0β  —  Last change: 19 August 1985