I've been a professional C, Perl, PHP and Python developer.
I'm an ex-sysadmin from the late 20th century.
These days I do more Javascript and CSS and whatnot, and promote UX and accessibility.
What it is, is that if I'm in a "non-trivial" script, and I'm using pushd and popd to keep a stack of where I am, and one function fails - for example, if pushd doesn't succeed because the directory is missing - then all subsequent commands will think I'm in the wrong place and potentially do destructive things.
On the face of it, cd has the same pitfalls, and if everything was defensively programmed, it wouldn't matter:
if!cd"$path";then# do some recoveryfi
if! push "$path";then# do some recoveryfi
But if that's what we're doing, we might as well use absolute paths and program defensively everywhere.
By trapping I mean things like this:
trap clean_up EXIT
clean_up(){# do whatever we need to put the system back where we left it.}
Given that scripts can be sourced as well as executed, changing directory within a script might or might not change the directory of the calling shell.
What it is, is that if I'm in a "non-trivial" script, and I'm using
pushdandpopdto keep a stack of where I am, and one function fails - for example, ifpushddoesn't succeed because the directory is missing - then all subsequent commands will think I'm in the wrong place and potentially do destructive things.On the face of it,
cdhas the same pitfalls, and if everything was defensively programmed, it wouldn't matter:But if that's what we're doing, we might as well use absolute paths and program defensively everywhere.
By trapping I mean things like this:
Given that scripts can be
sourced as well as executed, changing directory within a script might or might not change the directory of the calling shell.Sick! That's some pretty cool stuff. I'm going to look into that some more. Thank you for sharing!