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Full Discussion: pipe-fork-execve
Top Forums Programming pipe-fork-execve Post 302267975 by ivhb on Sunday 14th of December 2008 07:31:11 PM
Old 12-14-2008
Code:
int p[2];
pid_t pid;

pipe(p);
pid = fork();
# if 0 
/* delete them */
/* en.. pid == 0 also meets pid < 1 , so child ends here */
if( pid < 1 ){
/* bla bla */
close(p[0]);
close(p[1]);
return ;
}
# endif
if( pid == 0 ){
close(p[0]);

fcntl(p[1],F_SETFD,0) ; /* do not close on exec */ /* i think this is redundant */

execve("/bin/sh",arg,env);
int err = errno;
write(p[1],&err,sizeof(int)); /* why there is nothing received in my parent process */
_exit(127);
}

/* parent process */
close(p[1]);
if( read(p[0],&code,sizeof(int) ) < 0){
perror("nothing received");
/* this is true even if the execve() fail and there is something sent.. why */
}

 

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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
Upon successful completion, these functions return 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 |Standard | +-----------------------------+-----------------------------+ |MT-Level |Async-Signal-Safe | +-----------------------------+-----------------------------+ SEE ALSO
intro(2), exec(2), fork(2), getsid(2), setpgid(2), setpgrp(2), setsid(2), signal(3C), attributes(5), standards(5) SunOS 5.10 28 Dec 1996 getpid(2)
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