How to use unix/Linux low-level IO function
This article mainly introduces how to use the unix/Linux low-level IO function, which is very detailed and has a certain reference value. Friends who are interested must finish it!
The use of unix/Linux low-level IO functions, you must master to write module, the necessary application programming knowledge should have, otherwise, how to write applications to test your module or driver?
And the most important thing is to understand the interfaces called by the upper layer, and you will understand what the upper developers need and what they can achieve.
Put aside all the reading in your hand and get thoroughly familiar with the third chapter of the book on advanced programming in the Unix environment.
The contents include:
What exactly does open (), especially various common parameters, mean, such as creating an empty file: fd = open ("/ tmp/xx.txt", O_RDWR | O_CREAT | O_TRUNC)
Read a file, fd = open ("/ dev/hello", O_RDONLY)
If you want to write an existing file, fd = open ("/ dev/hello", O_WRONLY)
Specific parameters: man 2 open
Read ()
Write ()
Ioctl (), this is the most important.
Lseek (), the file pointer moves
For example, the following example:
Is to simply read a file:
# include
# include
# include
# include
Int main (int argc,char * * argv)
{
Int fd = 0
Int pid = 0
Char buffer [20] = {'\ 0'}
Char * read_buffer [20] = {'\ 0'}
/ / fd = open ("/ dev/hello", O_RDWR | O_CREAT | O_TRUNC)
Fd = open ("/ dev/hello", O_RDONLY); / / | O_NONBLOCK)
Printf ("fd=%d\ n", fd)
If (fd < 0) {
Perror ("/ dev/hello")
Return-1
}
Read (fd,read_buffer,sizeof (read_buffer)-1)
Printf ("read_buffer=%s\ n", read_buffer)
Close (fd)
Return 0
}
The following is a simple way to write a file
# include
# include
# include
# include
Int main (int argc,char * * argv)
{
Int fd = 0
Int pid = 0
Char buffer [20] = {'\ 0'}
Char write_buffer [20] = {'\ 0'}
Strcpy (write_buffer, "zhanglinbao")
Fd = open ("/ dev/hello", O_RDWR | O_CREAT | O_TRUNC)
/ / fd = open ("/ dev/hello", O_RDONLY)
Printf ("fd=%d\ n", fd)
If (fd < 0) {
Perror ("/ dev/hello")
Return-1
}
Write (fd,write_buffer,sizeof (write_buffer)-1)
Close (fd)
Return 0
}
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