A simple sendfile program, but not works

Question

#include <unistd.h> #include <stdio.h> #include <string.h> #include <sys/sendfile.h> #include <sys/stat.h> #include <fcntl.h> int main(){ int fd1,fd2,rc; off_t offset = 0; struct stat stat_buf; fd1=open("./hello.txt",O_RDONLY); //read only fd2=open("../",O_RDWR); //both read and write fstat(fd1, &stat_buf); //get the size of hello.txt printf("file size: %d\n",(int)stat_buf.st_size); rc=sendfile (fd2, fd1, &offset, stat_buf.st_size); }

So as you have seen, it's quite a simple program. But I just can't find hello.txt in ../ My aim is to see what happens if I put a whatever number, says 10, instead of st_size which may be hundreds of bytes.

Edit:

Thanks for your answers. Well, I followed your advice and changed

 fd2=open("../",O_RDWR);

to

 fd2=open("../hello.txt",O_RDWR);

Also, I checked the return value of fstat and sendfile, everything is ok.

But the problem is still the same.

have you checked that hello.txt is excites in previous folder.? — Jeegar Patel
– Jeegar Patel, Commented Oct 5, 2011 at 10:37
Hi @Mr.32 , did you mean exists? Well, the results shows that hello.txt won't be created in the previous folder. — sliter
– sliter, Commented Oct 5, 2011 at 11:37
in previous folder there should be hello.txt which you are going to open.. — Jeegar Patel
– Jeegar Patel, Commented Oct 5, 2011 at 11:40
well, I've also tried to creat a hello.txt manually or by just using O_RDWR|O_CREAT. So I can find the file there but it's just an empty file. — sliter
– sliter, Commented Oct 5, 2011 at 13:20

Mat · Accepted Answer · 2011-10-05 09:26:42Z

You need to specify the filename in the second open, not just the directory name.

Please be sure to check the return values of all these functions, including fstat.

CharlesB · Accepted Answer · 2011-10-05 09:26:53Z

2

Have you tried fd2 = open("../hello.txt",O_RDWR);?

answered Oct 5, 2011 at 9:26

CharlesB

91.2k29 gold badges203 silver badges228 bronze badges

1 Comment

sliter Over a year ago

Hi @CharlesB, I've followed your advice but the result is still the same

Jeegar Patel · Accepted Answer · 2011-10-05 09:44:55Z

1>

 fd1=open("./hello.txt",O_RDONLY); //read only fd2=open("../",O_RDWR); //both read and write

replace with

 fd1=open("../hello.txt",O_RDONLY); //read only fd2=open("../your_file_name",O_RDWR);

2>

 fstat(fd1, &stat_buf);

will fill up some info related to fd1 file in stat_buf . Here size of that file is also return in that structure with st_size element.

now in

 rc=sendfile (fd2, fd1, &offset, stat_buf.st_size);

total stat_buf.st_size bytes are going to send on fd2 file. if here if you write 10 then only 10 bytes will go in fd2.

Collectives™ on Stack Overflow

A simple sendfile program, but not works

3 Answers 3

Comments

1 Comment

Comments

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

1 Comment

Comments

Related