How to realize Pipeline Communication in Linux
How to achieve pipeline communication in Linux, many novices are not very clear about this, in order to help you solve this problem, the following small series will explain in detail for everyone, people who have this need can learn, I hope you can gain something.
I. Definitions
The pipeline is one-way, first-in, first-out. It connects the input of one program to the output of another. After the data is read by a process, it is deleted from the pipeline. It is divided into nameless and famous pipes. The former is used for communication between parent and child processes, while the latter is used for communication between two processes in the same system.
II. Unnamed pipeline
The code is as follows:
int pipe(int fd[2]);
Where fd[0] is used to read pipes and fd[1] is used to write pipes. Returns zero if successful,-1 otherwise, error reason stored in errno.
Third, the famous pipeline: FIFO
The code is as follows:
int mkfifo(const char* pathname,mode_t mode)
Use O_NONBLOCK when open, and immediately return an error if the access requirements cannot be met. Erron is ENXIO.
Examples:
The code is as follows:
fread. c//Read files
#include
#include
#define FIFO "myfifo"
main(){
int fd;
char buff[100];
if(access(FIFO,F_OK) == -1){
mkfifo(FIFO,0777);
}
fd=open(FIFO,O_RDONLY| O_NONBLOCK); //Set non-blocking on, otherwise it will block the read function when there is no input
int num;
while(1){
memset(buff,'\0', 100); //garbled if last character is not cleared
if((num=read(fd,buff,100))==0){
printf("waiting.....\ n");
sleep(1);
continue;
}
printf("read %d in fifo , it's %s",num,buff);
sleep(1);
}
}
fwrite. c//Write a file
#include
#include
#include
#define FIFO "myfifo"
main(){
int fd;
char buff[100];
memset(buff,'\0',100);
scanf("%s",buff);
if(access(FIFO,F_OK) == -1){
mkfifo(FIFO,0777);
}
fd=open(FIFO,O_WRONLY);
int num;
num=write(fd,buff,strlen(buff));
printf("%d char is written! It's %s\n",num,buff);
}
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