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I run grep some-string -r . &. While it is running in bkg, I cd to another directory. It seems that grep interprets the hard link . differently then. What happens before and after I change the current directory? Will both the original and the new directories not be searched completely?

I wonder if . as a command line argument to a command is only dereferenced at the start of running the command, or is dereferenced whenever it is used by the program during its running?

  • What differences in behaviour do you see? – Stephen Kitt Mar 20 '15 at 19:20
  • it found some files in the original working dir before I changed the working dir, and some files in the new working dir after I changed the working dir. – Tim Mar 20 '15 at 19:26
  • Was your new working directory a sub-directory of the initial working directory? – Stephen Kitt Mar 20 '15 at 19:28
  • If it doesn't reveal anything sensitive, would you mind copying and pasting grep's output? – Stephen Kitt Mar 20 '15 at 19:33
  • Can't reproduce it. Not sure why I got the strange result. – Tim Mar 20 '15 at 22:12
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Each process has its own "current working directory", which can't be changed from outside the process.

So when you do

grep some-string -r . &

your shell starts grep in the background, and grep's current working directory is initialised to the same value as the shell's at that moment. grep's definition of . here is its own current directory, not anything else's; the shell has no part in the argument's interpretation.

Subsequently changing the shell's directory using cd has no impact on grep...

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