On Wed, Apr 04, 2018 at 11:25:26AM +0800, 積丹尼 Dan Jacobson wrote: > $PS4 is for sh -x. Well, $PS5 or $PSv should be for sh -v! > > Imagine, with just a simple PS5='$ ', one could produce > perfect dialogues, > > $ set -eu /tmp/x > $ mkdir $@ > $ cd $@ > $ seq 3|xargs touch > $ ls -U $@ > 3 2 1
Until you use a compound command like "if" or "for" or "while", or a function. Then you suddenly realize how utterly useless sh -v actually is, and why nobody ever bothers with it. sh -v echoes lines as they ae *read* by the shell, not as they are executed. In the case of a compound command, the entire command has to be read before execution can begin. If the script consists almost entirely of a while loop (pretty common), then the entire while loop (i.e. the vast majority of the script) has to be read, and thus echoed by -v, before anything in the loop actually happens.
