about summary refs log tree commit diff stats
path: root/tests
diff options
context:
space:
mode:
authornfnty <git@nfnty.se>2017-02-06 02:30:28 +0100
committernfnty <git@nfnty.se>2017-02-06 02:30:28 +0100
commit9a619526f472cce3997b2aa89c13532cf8f005e1 (patch)
treee1eb8523806138b247bcd085c7203df9ed9a9930 /tests
parent41478b10c5a0bace85c74bc7388b3818c8f86ab4 (diff)
downloadranger-9a619526f472cce3997b2aa89c13532cf8f005e1.tar.gz
core.main: Catch the right traceback
Diffstat (limited to 'tests')
0 files changed, 0 insertions, 0 deletions
 

generated by cgit-pink 1.4.1-2-gfad0 (git 2.36.2.497.gbbea4dcf42) at 2024-11-29 12:14:33 +0000


 



36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115

116
117
118
119

120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136





















































































































                                                                              



                                                                          
















                                                                           
The "cd-after-exit" Feature

== Abstract

This document explains the troublesome implementation of the "cd-after-exit"
feature.


== 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. :)

Dec 25, 2009