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bashfifo

bash: a simple FIFO (first-in first-out) queue

I am looking for a portable bash solution for a simple FIFO queue. My queue input will always be a single line of text.I came up with a simple solution, which works well.

fifo_queue="fifo.txt";
fifo_tmp="fifo.tmp"

# put a new line into FIFO
echo "append to FIFO a line" >> $fifo_stack;

#get line back from FIFO
echo $(head -n1 "$fifo_queue")
tail -n +2 "$fifo_queue" > "$fifo_tmp" && mv "$fifo_tmp" "$fifo_queue"

Now the question: Is there a more elegant (i.e. easy understandable) way to retrieve the FIFO line. For example with a simple one-liner instead of two lines?

Solution

  • If you want to edit a file, use an editor; don't cobble something together with tail.

    put () {
    printf '%s\n' "$1" >> "$2"
}

get () {   
    printf '1p\n1d\nwq\n' | ed -s "$1"
}

    Then

    $ put a queue.txt
$ put b queue.txt
$ get queue.txt
a
$ put c queue.txt
$ get queue.txt
b