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diff --git a/doc/cd-after-exit.txt b/doc/cd-after-exit.txt deleted file mode 100644 index ee300518..00000000 --- a/doc/cd-after-exit.txt +++ /dev/null @@ -1,161 +0,0 @@ -The "cd-after-exit" Feature -=========================== - -Abstract --------- - -This document explains the troublesome implementation of the "cd-after-exit" -feature. - -This is written for developers who wonder how it's working. - - -Specification -------------- - -When the feature is enabled, ranger will attempt to change the directory of -the parent shell (from which ranger is run) to the last visited directory -when ranger is exited. - -This task is, by its nature, shell dependent. As a bash or zsh user, -I focused on the implementation for those two shells and left the -addition of support for csh, ksh, and other shells to those who actually use -those shells. - - -What's the problem? -------------------- - -Shells have several limitations, the implementation could not be done easily -because: - -1. It is not possible to use something like system('cd xyz') at the end. -This command would run in a new shell and wouldn't change the directory -of the parent shell at all. - -2. Using exec('cd xyz') is not possible either, since 'cd' is a command -which is directly integrated in to the shell and can not be run this way. - - -Redirection of streams ----------------------- - -The only way I found is using cd `program` from inside the shell to change -the directory to whatever `program` prints to the stdout: - - bash$ cd `echo ..` - -Since the user interface still has to be printed, we simply redirect it to -the stderr. It is not sufficient however to change sys.stdout to sys.stderr, -since curses seems not to be aware of sys.stdout and continues to print out -the interface to the actual stdout. - -So what I did was swap the stdout and stderr of the whole ranger process on -the shell command line by using: - - bash$ cd `ranger 3>&1 1>&2 2>&3 3>&-` - -Since errors are now printed to the stdout, we have do this in ranger: - sys.stderr = sys.__stdout__ - -And at the end, write the current directory to the stdout, which is now -reachable via sys.__stderr__ due to the redirections: - sys.__stderr__.write(last_visited_directory) - -To inform the ranger process about these changes, we add a --cd-after-exit -switch which: - bash$ cd `ranger --cd-after-exit 3>&1 1>&2 2>&3 3>&-` - - -Argument passing ----------------- - -This works well enough, but there are two remaining problems: - -1. How to pass arguments to ranger? - -2. How to memorize that line? Although you can just copy+paste it -into your bashrc and create an alias, the complexity of the line -could lead to errors. - -Both problems are solved by putting the command in a file: - -run.sh: - cd "`ranger --cd-after-exit \"$@\" 3>&1 1>&2 2>&3 3>&-`" - -The $@ is responsible for argument passing. By using the source command, -the file will be evaluated without creating a distinct new shell. - - bash$ source run.sh arg1 ... argN - -To add flexibility, replace the name "ranger" in the command to the first -argument. Now it requires you to pass the name of the ranger command to -the script as the first argument: - -run.sh: - RANGER="$1" - shift - cd "`$RANGER --cd-after-exit \"$@\" 3>&1 1>&2 2>&3 3>&-`" - - -Put it in a nutshell --------------------- - -I didn't want to have 2 files for the main program and wanted just one -file at /usr/bin/ranger. So I used this trick to merge both files into one: - - #!/usr/bin/python - """": - <shell code> - """ - <python code> - -If you run this file with python, or simply by typing ranger, the program will -run normally. If you, however, run this file by sourcing it into the shell, -like you did with run.sh, the cd-after-exit mode will be activated. - -Now the way of running ranger with the cd-after-exit feature is: - - bash$ source /path/to/ranger.py /path/to/ranger.py - -or, if properly installed: - - bash$ source ranger ranger - -A convenient way of using this feature is adding this line to your bashrc: - - alias rn='source ranger ranger' - - -Open issues ------------ - -Unfortunately there is some redundancy: you have to type the path to ranger -twice. I know of no way to fix this, because it is not possible to get the -filename of the file currently being sourced. - -Example: - - bash$ echo 'source sourced.sh' > main.sh - bash$ echo 'echo $0 $@' > sourced.sh - bash$ bash main.sh - main.sh - -If you find a way to make this print out 'sourced.sh', let me know. :) - -Another thing: If Ctrl+C is pressed anywhere in the program, the execution -of the sourced shell script is stopped and the feature stops working. - -This was handled by using a script like that: - - ranger_exec="$1" - shift - trap "" INT - exec 3< <($ranger_exec --cd-after-exit $@ 3>&1 1>&2 2>&3 3>&-) - while read ranger_output; do false; done <&3 - cd "$ranger_output" - #...and some clean ups - -but that won't work in zsh for some reason, so I took it out again. - -Dec 25, 2009 |