111 lines
1.7 KiB
C
111 lines
1.7 KiB
C
// C program to illustrate
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// non I/O blocking calls
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#include <stdio.h>
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#include <unistd.h>
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#include <fcntl.h> // library for fcntl function
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#include <stdlib.h>
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#include <errno.h>
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#include <sys/types.h>
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#define MSGSIZE 6
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char* msg1 ="hello";
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char* msg2 ="bye !!";
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void parent_read(int p[])
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{
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int nread;
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char buf[MSGSIZE];
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// write link
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close(p[1]);
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while (1) {
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// read call if return -1 then pipe is
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// empty because of fcntl
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nread = read(p[0], buf, MSGSIZE);
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switch (nread) {
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case -1:
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// case -1 means pipe is empty and errono
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// set EAGAIN
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if (errno == EAGAIN) {
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printf("(pipe empty)\n");
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sleep(1);
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break;
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}
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else {
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perror("read");
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exit(4);
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}
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// case 0 means all bytes are read and EOF(end of conv.)
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case 0:
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printf("End of conversation\n");
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// read link
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close(p[0]);
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exit(0);
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default:
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// text read
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// by default return no. of bytes
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// which read call read at that time
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printf("MSG = %s\n", buf);
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}
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}
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}
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void child_write(int p[])
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{
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int i;
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// read link
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close(p[0]);
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// write 3 times "hello" in 3 second interval
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for (i = 0; i < 3; i++) {
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write(p[1], msg1, MSGSIZE);
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sleep(3);
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}
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// write "bye" one times
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write(p[1], msg2, MSGSIZE);
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// here after write all bytes then write end
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// doesn't close so read end block but
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// because of fcntl block doesn't happen..
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exit(0);
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}
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int main()
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{
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int p[2];
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// error checking for pipe
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if (pipe(p) < 0)
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exit(1);
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// error checking for fcntl
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if (fcntl(p[0], F_SETFL, O_NONBLOCK) < 0)
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exit(2);
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// continued
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switch (fork()) {
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// error
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case -1:
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exit(3);
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// 0 for child process
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case 0:
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child_write(p);
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break;
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default:
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parent_read(p);
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break;
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}
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return 0;
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}
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