Stuck in an infinite while loop

Question

I am trying to write this code so that if the process reads map finished in the pipe it increments a variable by 1 so that it eventually breaks out of the while loop. Otherwise it will add unique parameters to a keys file. However it goes into an infinite loop and never breaks out of the loop.

while [ $a -le 5 ]; do
    read input < map_pipe;
    if [ $input = "map finished" ]; then
            ((a++))
            echo $a
    else
            sort -u map_pipe >> keys.txt;
    fi
done

Answer 1

I decided to fix it for you, not sure if this is what you wanted, but I think I am close:

#!/bin/bash
a=0 #Initialize your variable to something
while [ $a -le 5 ]; do
    read input < map_pipe;
    if [ "$input" = "map finished" ]; then #Put double quotes around variables to allow values with spaces
        a=$(($a + 1)) #Your syntax was off, use spaces and do something with the output
    else
        echo $input >> keys.txt #Don't re-read the pipe, it's empty by now and sort will wait for the next input
        sort -u keys.txt > tmpfile #Instead sort your file, don't save directly into the same file it will break
        mv tmpfile keys.txt
        #sort -u keys.txt | sponge keys.txt #Will also work instead of the other sort and mv, but sponge is not installed on most machines
    fi  
done