Dynamically computed Bash variable

I have several similarly structured directory trees. something like: ~/ Tree1/ src/

bin/ Tree2/ src/ bin/

When I somewhere below Tree1/src I want to work with Tree1/bin开发者_如何转开发. When I somewhere below Tree2/src I want to work with Tree2/bin.

Is there a way to define a shell variable whose value depends on my current working directory?

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PWD is a variable already set to your current directory by bash, ksh and other shells.

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cwd=$(pwd) should do the trick. It assigns the output of print working directory (pwd) to a variable.

To replace ~Tree1/src/dir1/dir2 with ~Tree1/bin you could do

bindir=$(pwd | sed 's/src.*/bin/')

See also Command Substitution

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As jlliagre stated, bash (as many other modern shells) stores the current working directory in $PWD; if it is Tree1/src/some/other/directory, then you can extract "Tree1/bin" from it by just using "parameter expansion":

$ echo $PWD
Tree1/src/some/other/directory

$ echo ${PWD%%src*}bin
Tree1/bin

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Generally $PWD variable (Present Working Directory) contains the path to the current directory. If this variable is not defined, you can use the pwd command that will return the current path.

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Two other definitions of "current" include the directory you were in when the script was started (which is the value of start_dir="$PWD" at the start of the file, no matter where the script is) and the directory of the script itself - script_dir="$(dirname -- "$(readlink -f -- "$0")")".