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I have a general question as to why this occurs, and a misconception about 'pwd'.

You start with directory /test and in it you have /test/folder1.

Folder 1 has: file1.txt

In 2 separate terminals we "cd /test", and do an "ls" and discover folder1 as the output for both of these terminals.

We now "cd folder1" on terminal one. Terminal two remains in /test.

If we then "mv folder1 folder2" on terminal two and run an "ls" we get folder2 as the output. Clearly indicating our mv was successful.

However, within terminal 1 (which was in /test/folder1) if we run a "pwd" the output remains /test/folder1. Ie: it does NOT reflect that we have since moved the folder to /test/folder2.

Why is this the case? I can understand why if we were to edit the file1.txt it is just a pointer within the file system that should be pointing to the same file. Indeed it is as you can modify the file in each terminal and see the edits in the other. However, why is it the case that the 'pwd' command no longer reflects the actual path to that directory?

Thanks!

user3380636
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2 Answers2

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Assuming you're using bash, pwd is showing you the value of the PWD environment variable, which is updated when you change directory with cd. The folder1 directory changing name does not cause bash to update PWD. However you can find evidence that the directory has changed name:

  • pwd -P will show the new name of the directory.
  • ls -l /proc/self/cwd will link to the new name.
Richard Fearn
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I think it is just the case that the first terminal has no reason to re-evaluate where it is. If you do the following command in the first terminal

cd .

you will see your current working directory has indeed changed per the rename (mv).

Mark Setchell
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    Shouldn't the "pwd" call always reflect a correct directory path? I understand that would require either a notify the directory has been moved to all processes (not feasible) or a more robust implementation of "pwd" which more accurately represents this. I'm just curious as to if someone with more technical experience has the answer as to why it's not done this way. – user3380636 Mar 04 '14 at 20:06
  • `/bin/pwd` gets it right, but the shell's built-in `pwd` does shortcuts that make it get it wrong - the price of speed. – Mark Setchell Mar 04 '14 at 20:08