If you use csh, you may know about directory stacks. The pushd
command puts the current directory on the stack, and changes to a new
directory; the popd command pops a directory off the stack and
changes to it.
phoenix% cd phoenix% PROMPT='Z %~> ' Z ~> pushd /tmp /tmp ~ Z /tmp> pushd /usr/etc /usr/etc /tmp ~ Z /usr/etc> pushd /usr/bin /usr/bin /usr/etc /tmp ~ Z /usr/bin> popd /usr/etc /tmp ~ Z /usr/etc> popd /tmp ~ Z /tmp> pushd /etc /etc /tmp ~ Z /etc> popd /tmp ~
zsh's directory stack commands work similarly. One difference is the
way pushd is handled if no arguments are given. As in csh, this
exchanges the top two elements of the directory stack:
Z /tmp> dirs /tmp ~ Z /tmp> pushd ~ /tmp
unless the stack only has one entry:
Z ~> popd /tmp Z /tmp> dirs /tmp Z /tmp> pushd ~ /tmp
or unless the PUSHDTOHOME option is set:
Z ~> setopt pushdtohome Z ~> pushd ~ ~ /tmp
As an alternative to using directory stacks in this manner, we can get something like a directory history by setting a few more options and parameters:
~> DIRSTACKSIZE=8 ~> setopt autopushd pushdminus pushdsilent pushdtohome ~> alias dh='dirs -v' ~> cd /tmp /tmp> cd /usr /usr> cd bin /usr/bin> cd ../pub /usr/pub> dh 0 /usr/pub 1 /usr/bin 2 /usr 3 /tmp 4 ~ /usr/pub> cd -3 /tmp> dh 0 /tmp 1 /usr/pub 2 /usr/bin 3 /usr 4 ~ /tmp> ls =2/df /usr/bin/df /tmp> cd -4 ~>
Note that =2 expanded to the second directory in the history
list, and that cd -3 recalled the third directory in the
list.
You may be wondering what all those options do. AUTOPUSHD made
cd act like pushd. (alias cd=pushd is not
sufficient, for various reasons.) PUSHDMINUS swapped the meaning
of cd +1 and cd -1; we want them to mean the opposite of
what they mean in csh, because it makes more sense in this scheme, and
it's easier to type:
~> dh 0 ~ 1 /tmp 2 /usr/pub 3 /usr/bin 4 /usr ~> unsetopt pushdminus ~> cd +1 /tmp> dh 0 /tmp 1 ~ 2 /usr/pub 3 /usr/bin 4 /usr /tmp> cd +2 /usr/pub>
PUSHDSILENT keeps the shell from printing the directory stack
each time we do a cd, and PUSHDTOHOME we mentioned
earlier:
/usr/pub> unsetopt pushdsilent /usr/pub> cd /etc /etc /usr/pub /tmp ~ /usr/bin /usr /etc> cd ~ /etc /usr/pub /tmp ~ /usr/bin /usr ~> unsetopt pushdtohome ~> cd /etc ~ /usr/pub /tmp ~ /usr/bin /usr /etc>
DIRSTACKSIZE keeps the directory stack from getting too large,
much like HISTSIZE:
/etc> setopt pushdsilent /etc> cd / /> cd / /> cd / /> cd / /> cd / /> cd / /> cd / /> cd / /> dh 0 / 1 / 2 / 3 / 4 / 5 / 6 / 7 /