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Top Forums UNIX for Advanced & Expert Users Inter-process communication:pipes,doors,etc. Post 302159800 by adderek on Friday 18th of January 2008 04:39:29 PM
Old 01-18-2008
Maybe I will give you some more details.
I was to take code created by someone else. For logging from several simultaneous processes they are using many log files and from time to time they merge them all into one.
Until now I was thinking that when you are doing:
Code:
print "some even quite long message" >> file.txt

from several processes at once, then it would not interfere.
But they told me that they were receiving logs like:
"log number one
log numbelog number threer two
log number four"
Im ,y understanding this should never occur. But if this is the case then FIFO pseudo-device would be the best choice.
Anyway - I asked because according to my knowledge situation described by the other guy should not occur unless he is doing something like:
Code:
print "log number " >>file.txt
print "one" >>file.txt

 

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filter_create_fd(3)						   util/filter.h					       filter_create_fd(3)

NAME
filter_create_fd - Create a sub process and return the requested pipes SYNOPSIS
#include <util/filter.h> NEOERR *filter_create_fd(const char *cmd, int *fdin, int *fdout, int *fderr, pid_t *pid); ARGUMENTS
cmd -> the sub command to execute. Will be executed with /bin/sh -c fdin -> pointer to return the stdin pipe, or NULL if you don't want the stdin pipe fdout -> pointer to return the stdout pipe, or NULL if you don't want the stdout pipe fderr -> pointer to return the stderr pipe, or NULL if you don't want the stderr pipe DESCRIPTION
filter_create_fd and filter_create_fp are what popen been: a mechanism to create sub processes and have pipes to all their input/output. The concept was taken from mutt, though python has something similar with popen3/popen4. You control which pipes the function returns by the fdin/fdout/fderr arguments. A NULL value means "don't create a pipe", a pointer to an int will cause the pipes to be created and the value of the file descriptor stored in the int. You will have to close(2) the file descriptors yourself. RETURN VALUE
fdin -> the stdin file descriptor of the sub process fdout -> the stdout file descriptor of the sub process fderr -> the stderr file descriptor of the sub process pid -> the pid of the sub process SEE ALSO
filter_wait(3), filter_create_fp(3), filter_create_fd ClearSilver 12 July 2007 filter_create_fd(3)
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