Sendfile example

The sendfile call can be used in many places to make copies more efficient. Node Express with passing data along. Send and Receive a file in socket programming in Linux with C. How to receive a file using sendfile?

It allows you to have some sort of sanity-checking before committing to downloading whatever the server tries to send.

What if the server sends the . In this article I will explore sendfile , what it does, and how to use it, illustrated by some example programs. The Linux Programming Interface. Because this copying is done within the kernel, sendfile () is more efficient than the combination of read(2) and write(2), which would require transferring data to and from user space. C Programming in Linux Tutorial using GCC compiler. Thus, the usage of sendfile () in server applications can significantly reduce CPU load.

Replacing read() with mmap() in our example will not change much.

However, the mmap syscall is asking to map some bytes from the file (or other object) specified by the file descriptor into virtual memory. As its name implies, zero-copy allows us to operate on data without copying it, or, at least, by minimizing the amount of copying going on. Zero Copy I: User-Mode Perspective describes the technique, with some nice diagrams and a description of the sendfile () system call.

Rewriting my example above with . Enabling the sendfile directive eliminates the step of copying the data into the buffer and enables direct copying data from one file descriptor to another. The most significant bits of flags specify amount of pages that sendfile may read ahead when reading the file. A macro SF_FLAGS() is provided to combine readahead amount and flags. This benchmark script implements the two examples above and compares plain socket. CPU time spent and bytes transmitted per second resulting in sendfile () being about 2. These are the I get on my Linux 2. Now we have the foundation for our quick Node app.

Next, we will configure a virtual host static. It uses ssh for data transfer and provides the same authentication and same level of security as ssh. Example Transferring Files to Sockets. This is an example of setting up X- Sendfile in Apache.

You must have the mod_xsendfile Apache module, which you can get here.

Download the one appropriate for your operating system and Apache version, and put it into your Apache . This example illustrates how to use the ssh-keygen command to generate a public key on the management node, then the scp command to copy the key to the remote system. Exception as e: return str(e). Simple enough, but what if you want to protect the files in some way. ExpressJS allows you to develop custom web server according to your need. In this short tutorial i am going to explain how to render HTML files in ExpressJS.

About sendFile () function. But one concern arises: waht if my webpage need include an external javascript file? In the following example , the XCOMcommand is used. The configuration file is MYCONFIG.

CNF, the local file is named TESTA. AAA, the remote file is named TESTB. BBB, and the transferred file replaces a file on the remote system that already exists. The PROTOCOL parameter specifies the protocol as .