I can not find "/ls.txt", gives an error for a slash.

du -a | awk '{if(//ls.txt$){print $2}}'

    1 answer 1

     //ls.txt$

    This is an incorrect regular expression entry. will be correct:

     /ls.txt$/

    and if you need to include in the expression and slash, then it must be "zaasekit":

     /\/ls.txt$/

    ps by the way, and you have an extra conditional operator. The awk program can immediately select lines that fall under a regular expression:

     awk '/выражение/{действия}'

    in your example:

     $ du -a | awk '/\/ls.txt$/{print $2}'