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; for truncate the user must have write permission for 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

Truncate succeeds unless:

[ENOENT] The pathname was too long. 

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

[ENOENT] A component of the path name is too long. 

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

[EACCES] Write permission is denied on the file. 

[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.  The reliable detection of this error will be implementation dependent. 

[ENAMETOOLONG]
The path name exceeds MAXPATHLEN characters.

Ftruncate succeeds unless:

[EBADF] The fd is not a valid descriptor. 

[EINVAL] The fd references a file that was opened without write permission. 

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

AUTHOR

Truncate was developed by the University of California, Berkeley California, Computer Science Division, Department of Electrical Engineering and Computer Science. 

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. 

Hewlett-Packard Company  —  May 11, 2021