I use zsh on the command line, but I write run bash shell scripts so that they are portable.
I found out about IO redirection from here when I realized this difference:
Note that the command is just arbitrary, the first line of which is above stderr, and the second line is above stdout.
zsh on OS X:
% ls -ld /tmp /tnt 1>&2 2>&1 | sed -e 's/^/++/' ls: /tnt: No such file or directory ++ls: /tnt: No such file or directory lrwxr-xr-x@ 1 root wheel 11 Oct 19 2012 /tmp -> private/tmp ++lrwxr-xr-x@ 1 root wheel 11 Oct 19 2012 /tmp -> private/tmp
bash :
bash-3.2$ ls -ld /tmp /tnt 1>&2 2>&1 | sed -e 's/^/++/' ls: /tnt: No such file or directory lrwxr-xr-x@ 1 root wheel 11 Oct 19 2012 /tmp -> private/tmp
I find it difficult to determine the output of zsh .
Also, on Linux, the output order is slightly different for zsh :
% ls -ld /tmp /tnt 1>&2 2>&1 | sed -e 's/^/++/' ls: cannot access /tnt: No such file or directory drwxrwxrwt. 13 root root 4096 Dec 19 23:11 /tmp ++ls: cannot access /tnt: No such file or directory ++drwxrwxrwt. 13 root root 4096 Dec 19 23:11 /tmp
bash output is identical.
More experiments in zsh :
% ls -ld /tmp /tnt 1>&2 | sed -e 's/^/++/' ls: /tnt: No such file or directory lrwxr-xr-x@ 1 root wheel 11 Oct 19 2012 /tmp -> private/tmp ++lrwxr-xr-x@ 1 root wheel 11 Oct 19 2012 /tmp -> private/tmp % ls -ld /tmp /tnt 2>&1 | sed -e 's/^/++/' ++ls: /tnt: No such file or directory ++lrwxr-xr-x@ 1 root wheel 11 Oct 19 2012 /tmp -> private/tmp
This last gives the same results for bash .
I suppose I should prefer to learn bash behavior inside out before delving into how zsh ticking, but that’s not entirely ideal, because the odds are at least half the IO redirection that I expect to be, which I I definitely want to try from the zsh invitation. And in fact, I really invested in zsh , because I have a ton of custom plugins, and at that point it would be a big step to make a big switch to bash.