Wrong read from a named pipe - bash

Question

I have a script which reads commands from a named pipe:
#! /usr/bin/env bash
host_pipe="host-pipe"
#pipe for executing commands
[ -p "$host_pipe" ] || mkfifo -m 0600 "$host_pipe" || exit 1
chmod o+w "$host_pipe"
set -o pipefail
while :; do
if read -r cmd <$host_pipe; then
if [ "$cmd" ]; then
printf 'Running: %s \n' "$cmd"
fi
fi
done
I run it and test with command:
bash -c "echo 'abcdef' > host-pipe"
bash -c "echo 'abcdef' > host-pipe"
bash -c "echo 'abcdef' > host-pipe"
bash -c "echo 'abcdef' > host-pipe"
And get the strange output:
Running: abcdf
Running: abcdef
Running: abcde
Running: abcdf
Running: ace
Somehow the script can't read all the string it get from the pipe? How to read it?

Answer 1

You must have more than one reader of the named pipe host-pipe running for this to happen.
Check to see if you have a second instance of the script running in the background or possibly in another terminal.
Explanation
You will find that bash will issue reads from the pipe 1 byte at a time. If you are on Linux, you can strace your script. Here is an excerpt:
open("host-pipe", O_RDONLY|O_LARGEFILE) = 3
fcntl64(0, F_GETFD) = 0
fcntl64(0, F_DUPFD, 10) = 10
fcntl64(0, F_GETFD) = 0
fcntl64(10, F_SETFD, FD_CLOEXEC) = 0
dup2(3, 0) = 0
close(3) = 0
ioctl(0, TCGETS, 0xbf99bfec) = -1 ENOTTY (Inappropriate ioctl for device)
_llseek(0, 0, 0xbf99c068, SEEK_CUR) = -1 ESPIPE (Illegal seek)
read(0, "a", 1) = 1
read(0, "b", 1) = 1
read(0, "c", 1) = 1
read(0, "d", 1) = 1
read(0, "e", 1) = 1
read(0, "f", 1) = 1
read(0, "\n", 1) = 1
dup2(10, 0) = 0
fcntl64(10, F_GETFD) = 0x1 (flags FD_CLOEXEC)
close(10) = 0
Once you have more than one process with this consumption pattern, any single process will see lost characters.