cd Command Linux and Mystery Flags
- by Jason R. Mick
Platform: CentOS 6.2 Shell:tcsh
I'm playing around with cd for a BASH script, and noticed the wondrous cd - option, but was left with many questions...
Why the cd -? Isn't this redundant with cd ..? EDIT [As FatalError points out, these two commands don't do the same things... so the answer is "no"]
Can you delve farther back into your history with - flag, a la in a browser? e.g. When I type cd -, it takes me to my previous directory, but then if I enter that command again, it takes me to the directory I just came from, creating a sort of loop. Is a shorthand for going back multiple levels supported?EDITI realize I can go back with cd .., but was hoping this could be a gateway to a less verbose deep back, e.g. cd -3 vs. cd ../../../ ... hopefully that clarifies what I'm asking....EDIT2As to the current feedback, while .. is a special directory, I don't see a reason why the built-in cd to the terminal couldn't use a shorthand for ../../ ... ../ e.g. cd ..5 or why the built-in also couldn't have a history (a la auto pushd/popd) that could be turned on and used like cd -3. I get that this could be somewhat of security/privacy risk, but I don't see how it's any worst than storing a command history, which most shells/terminals do.
The manpage for cd, accessible via man cd and help cd (it's the same for either command), only lists -L and -P flags. However when I type in cd --help it outputs Usage: cd [-plvn][-|<dir>].. Am I right in assuming the other flags and the - (back) option are nonstandard?
What are the -n and -v flags for? Both seem to take me back to my home directory, that's all I've been able to figure out via experimentation.
A quick read on web resources [1][2] offered just the same sort of info that the man page did and didn't answer my questions.
Note: The second Linux-centric resource above claimed cd only had two options (obviously not true in current CentOS) hence my assumption that this functionality could be non-standard.
