Showing atomic consistency of Unix PIPES in BASH.

pipe.sh

#!/bin/bash 


set -e 

pipe_name="test_pipe"


# --------------------------------------------------------------------------- #

pipe_ostream () {
  
  char="$1"

  data=$(for i in {1..1024}; do printf "$1"; done;) 
  
  printf $data | dd iflag=fullblock if=/dev/stdin of=$pipe_name \
                    ibs=1024 \
                    obs=1024 \
                    count=1
}


pipe_istream () {
  
  o_file="$1"
  
  dd if="$pipe_name"  of=$o_file       \
     iflag=fullblock  \
     ibs=1024         \
     obs=1024         \
     count=1
}

# --------------------------------------------------------------------------- #

# CLEANUP 

if [ -e $pipe_name ]; then 
  rm $pipe_name 
fi

mkfifo $pipe_name 

if [ -e out.a ]; then rm out.a; fi
if [ -e out.b ]; then rm out.b; fi
if [ -e out.c ]; then rm out.c; fi
if [ -e out.d ]; then rm out.d; fi

sleep .2 


# - THIS WORKS ---------------------------------------------------------------- 

#pipe_ostream "a" & 
#pipe_ostream "b" &
#pipe_ostream "c" &
#pipe_ostream "d" &
#
#pipe_istream "out.a" 
#pipe_istream "out.b" 
#pipe_istream "out.c" 
#pipe_istream "out.d" 
#
#wait 
#exit 0 


# - THIS FAILS ---------------------------------------------------------------- 

#pipe_istream "out.a" & 
#pipe_istream "out.b" &
#
#pipe_ostream "a" 
#pipe_ostream "b" 
#
#wait 
#exit 0