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Full Discussion: fork() fd
Top Forums Programming fork() fd Post 16199 by Herman on Tuesday 26th of February 2002 10:21:42 PM
Old 02-26-2002
fork() fd
I run this code, actually I want to both processes print the message from "data". But only one does. What happens? Anyone can help?


#include <stdio.h>
main(){

int fd, pid;
char x;


fd = open("data",0); /* open file "data" */
pid = fork();

if(pid != 0){
wait(0);
printf("PID = %d.\n", getpid());
printf("FD = %d.\n",fd);
while (read(fd, &x, 1)){
write(1, &x, 1);
}
}
else{
printf("PID = %d.\n", getpid());
printf("PD= %d.\n",fd);
while (read(fd, &x, 1))
write(1, &x, 1);
}
}

The out put from the code:

This is a test.
PID = 4985.
PD= 3.
PID = 4984.
FD = 3.
 

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LEARN ABOUT OPENSOLARIS

getppid

getpid(2)							   System Calls 							 getpid(2)

NAME

       getpid, getpgrp, getppid, getpgid - get process, process group, and parent process IDs

SYNOPSIS

       #include <unistd.h>

       pid_t getpid(void);

       pid_t getpgrp(void);

       pid_t getppid(void);

       pid_t getpgid(pid_t pid);

DESCRIPTION

       The getpid() function returns the process ID of the calling process.

       The getpgrp() function returns the process group ID of the calling process.

       The getppid() function returns the parent process ID of the calling process.

       The getpgid() function returns the process group ID of the process whose process ID is equal to pid, or the process group ID of the calling
       process, if pid is equal to 0.

RETURN VALUES

       The getpid(), getpgrp(), and getppid() functions are always successful and no return value is reserved to indicate an error.

       Upon successful completion, getpgid() returns the process group ID. Otherwise, getpgid() returns (pid_t)-1 and sets errno to  indicate  the
       error.

ERRORS

       The getpgid() function will fail if:

       EPERM	The  process  whose process  ID is equal to pid is not in the same session as the calling process, and the implementation does not
		allow access to the process group ID of that process from the calling process.

       ESRCH	There is no process with a process ID equal to pid.

       The getpgid() function may fail if:

       EINVAL	 The value of the pid argument is invalid.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Committed 		   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |Async-Signal-Safe 	   |
       +-----------------------------+-----------------------------+
       |Standard		     |See standards(5). 	   |
       +-----------------------------+-----------------------------+

SEE ALSO

       Intro(2), exec(2), fork(2), getsid(2), setpgid(2), setpgrp(2), setsid(2), signal(3C), attributes(5), standards(5)

SunOS 5.11							    27 Jan 2009 							 getpid(2)
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