Terminal stops finding tcsh directory after some time

Question

On my system I have zsh and tcsh installed. I usually use zsh but some scripts use tcsh. Normally, in a terminal window, if I type

tcsh
mec-0569x:~> 

I get the prompt up as expected. If the terminal window has been open for a while, however, and I type tcsh, I get

tcsh
tcsh: No such file or directory
tcsh: Trying to start from "/home/james"
mec-0569x:~> 

I'm not sure if it's related to the time the window has been open, or a particular script I'm running in the window, but if I close the terminal window and open a new one, change directory to the folder I was in, it works perfectly fine. What should I be looking for to solve this?

Answer 1

The problem is probably that the directory you were in was removed, and that a new directory with the same pathname was created after that.

This is not the same directory; getcwd() uses inodes to get the pathname of a directory, this new directory has a different inode, and the inode getcwd() want to use doesn't exist anymore.
When you type tcsh, it inherits the (nonexistent) working directory from the parent process; on startup, tcsh wants to chdir() to the current working directory, but this doesn't exist anymore, so you get an error (and it chdir()s to the home directory).

You can solve this by cd-ing to the full pathname with cd "$PWD" before starting tcsh, this sets the correct working directory for the parent process.