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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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LEARN ABOUT SUNOS

pid

pid(n)                                                         Tcl Built-In Commands                                                        pid(n)

__________________________________________________________________________________________________________________________________________________

NAME

       pid - Retrieve process identifiers

SYNOPSIS

       pid ?fileId?
_________________________________________________________________

DESCRIPTION

       If  the  fileId  argument is given then it should normally refer to a process pipeline created with the open command.  In this case the pid
       command will return a list whose elements are the process identifiers of all the processes in the pipeline, in order.   The  list  will  be
       empty if fileId refers to an open file that is not a process pipeline.  If no fileId argument is given then pid returns the process identi-
       fier of the current process.  All process identifiers are returned as decimal strings.

EXAMPLE

       Print process information about the processes in a pipeline using the SysV ps program before reading the output of that pipeline:

              set pipeline [open "| zcat somefile.gz | grep foobar | sort -u"]
              # Print process information
              exec ps -fp [pid $pipeline] >@stdout
              # Print a separator and then the output of the pipeline
              puts [string repeat - 70]
              puts [read $pipeline]
              close $pipeline

SEE ALSO

       exec(n), open(n)

KEYWORDS

       file, pipeline, process identifier

Tcl                                                                     7.0                                                                 pid(n)
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