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:

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

EINVAL path contains a character with the high-order bit set. 

ENAMETOOLONG
The length of a component of path exceeds 255 characters, or the length of path exceeds 1023 characters. 

ENOENT The file referred to by path does not exist. 

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

EACCES Write permission is denied for the file referred to by path.

ELOOP Too many symbolic links were encountered in translating path.

EISDIR The file referred to by path is 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. 

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

EFAULT path points outside the process’s allocated address space. 

ftruncate succeeds unless:

EINVAL fd is not a valid descriptor of a file open for writing. 

EINVAL 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(2V)

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 3.2  —  Last change: 16 July 1986