from small one page howto to huge articles all in one place
 

search text in:





Poll
What does your sytem tell when running "ulimit -u"?








poll results

Last additions:
using iotop to find disk usage hogs

using iotop to find disk usage hogs

words:

887

views:

125119

userrating:

average rating: 1.7 (86 votes) (1=very good 6=terrible)


May 25th. 2007:
Words

486

Views

235570

why adblockers are bad


Workaround and fixes for the current Core Dump Handling vulnerability affected kernels

Workaround and fixes for the current Core Dump Handling vulnerability affected kernels

words:

161

views:

116195

userrating:

average rating: 1.3 (28 votes) (1=very good 6=terrible)


April, 26th. 2006:

Druckversion
You are here: manpages





COPY

Section: Linux Programmer's Manual (2)
Updated: 2017-09-15
Index Return to Main Contents
 

NAME

copy_file_range - Copy a range of data from one file to another  

SYNOPSIS

#include <sys/syscall.h>
#include <unistd.h>

ssize_t copy_file_range(int fd_in, loff_t *off_in,
                        int fd_out, loff_t *off_out,
                        size_t len, unsigned int flags);
 

DESCRIPTION

The copy_file_range() system call performs an in-kernel copy between two file descriptors without the additional cost of transferring data from the kernel to user space and then back into the kernel. It copies up to len bytes of data from file descriptor fd_in to file descriptor fd_out, overwriting any data that exists within the requested range of the target file.

The following semantics apply for off_in, and similar statements apply to off_out:

*
If off_in is NULL, then bytes are read from fd_in starting from the file offset, and the file offset is adjusted by the number of bytes copied.
*
If off_in is not NULL, then off_in must point to a buffer that specifies the starting offset where bytes from fd_in will be read. The file offset of fd_in is not changed, but off_in is adjusted appropriately.

The flags argument is provided to allow for future extensions and currently must be to 0.  

RETURN VALUE

Upon successful completion, copy_file_range() will return the number of bytes copied between files. This could be less than the length originally requested.

On error, copy_file_range() returns -1 and errno is set to indicate the error.  

ERRORS

EBADF
One or more file descriptors are not valid; or fd_in is not open for reading; or fd_out is not open for writing; or the O_APPEND flag is set for the open file description referred to by fd_out.
EINVAL
Requested range extends beyond the end of the source file; or the flags argument is not 0.
EIO
A low-level I/O error occurred while copying.
ENOMEM
Out of memory.
ENOSPC
There is not enough space on the target filesystem to complete the copy.
EXDEV
The files referred to by file_in and file_out are not on the same mounted filesystem.
 

VERSIONS

The copy_file_range() system call first appeared in Linux 4.5.  

CONFORMING TO

The copy_file_range() system call is a nonstandard Linux extension.  

NOTES

If file_in is a sparse file, then copy_file_range() may expand any holes existing in the requested range. Users may benefit from calling copy_file_range() in a loop, and using the lseek(2) SEEK_DATA and SEEK_HOLE operations to find the locations of data segments.

copy_file_range() gives filesystems an opportunity to implement "copy acceleration" techniques, such as the use of reflinks (i.e., two or more i-nodes that share pointers to the same copy-on-write disk blocks) or server-side-copy (in the case of NFS).  

EXAMPLE

#define _GNU_SOURCE #include <fcntl.h> #include <stdio.h> #include <stdlib.h> #include <sys/stat.h> #include <sys/syscall.h> #include <unistd.h>

static loff_t copy_file_range(int fd_in, loff_t *off_in, int fd_out,
                loff_t *off_out, size_t len, unsigned int flags) {
    return syscall(__NR_copy_file_range, fd_in, off_in, fd_out,
                   off_out, len, flags); }

int main(int argc, char **argv) {
    int fd_in, fd_out;
    struct stat stat;
    loff_t len, ret;


    if (argc != 3) {
        fprintf(stderr, "Usage: %s <source> <destination>\n", argv[0]);
        exit(EXIT_FAILURE);
    }


    fd_in = open(argv[1], O_RDONLY);
    if (fd_in == -1) {
        perror("open (argv[1])");
        exit(EXIT_FAILURE);
    }


    if (fstat(fd_in, &stat) == -1) {
        perror("fstat");
        exit(EXIT_FAILURE);
    }


    len = stat.st_size;


    fd_out = open(argv[2], O_CREAT | O_WRONLY | O_TRUNC, 0644);
    if (fd_out == -1) {
        perror("open (argv[2])");
        exit(EXIT_FAILURE);
    }


    do {
        ret = copy_file_range(fd_in, NULL, fd_out, NULL, len, 0);
        if (ret == -1) {
            perror("copy_file_range");
            exit(EXIT_FAILURE);
        }


        len -= ret;
    } while (len > 0);


    close(fd_in);
    close(fd_out);
    exit(EXIT_SUCCESS); }  

SEE ALSO

lseek(2), sendfile(2), splice(2)  

COLOPHON

This page is part of release 4.13 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.


 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
VERSIONS
CONFORMING TO
NOTES
EXAMPLE
SEE ALSO
COLOPHON





Other free services
toURL.org
Shorten long
URLs to short
links like
http://tourl.org/2
tourl.org
.
Reverse DNS lookup
Find out which hostname(s)
resolve to a
given IP or other hostnames for the server
www.reversednslookup.org
rdf newsfeed | rss newsfeed | Atom newsfeed
- Powered by LeopardCMS - Running on Gentoo -
Copyright 2004-2018 Sascha Nitsch Unternehmensberatung UG(haftungsbeschränkt)
Valid XHTML1.1 : Valid CSS : buttonmaker
- Level Triple-A Conformance to Web Content Accessibility Guidelines 1.0 -
- Copyright and legal notices -
Time to create this page: 3.2 ms