Bash Terminal – Consistent Way to Mangle Terminal

bashshellterminal

I'm on OSX 10.11.1 and occasionally my bash terminal gets mangled. It often happens when I accidentally cat a binary file. The result can be seen on the image below. The output becomes weird, and I can't type ascii characters anymore.

Even though this happens occasionally, I couldn't find a way to consistently reproduce the issue. Online search recommends doing cat /bin/*, but that works sporadically, only after a couple dozen tries.

I want to do this so I can find an easy solution how to handle this in tmux.

How do I consistently get bash to a "mangled" state? Is there maybe a magic unicode character that can do this?

Best Answer

This looks like the DEC special graphics character set.

Reading the xterm control sequences docs, it sounds like the terminal uses those when receiving ESC ( 0.

So you should be able to reproduce using

printf '\033(0'

printf '\033(0' > corrupt-my-terminal
cat corrupt-my-terminal

And get back using

printf '\033(B'

which according to the same page selects USASCII.

Other ways to restore the state include

tput sgr0  # resets all terminal attributes to their defaults

and

reset      # reinitializes the terminal

You could tput sgr0 in your PROMPT_COMMAND (bash), or precmd (zsh) to ensure it always gets reset automatically.

Or you could just make sure to use less, vim, or anything other than cat to view a file.

To make less act like cat and automatically quit if the file is under one page long, run less -FX, or do export LESS=-FX.

Or if you don't want to always use those less options, make a new alias, e.g.

alias c='less -FX'

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Bash – What’s the right way to sort a associated array in bash or zsh

Zsh has a built-in way to sort lists. However, I don't think there's a way to sort the values while keeping the correlation with the keys using parameter expansion flags and subscript flags, which means that an explicit loop is necessary. Assuming that your values don't contain a null character, you can build an array containing the values and keys concatenated with a null character in between, and sort that.

keys=("${(@k)A}")
values=("${(@v)A}")
combined=()
for ((i=1; i <= $#values; i++)) { combined[i]=($values[i]$'\0'$keys[i]); }
keys_sorted_by_decreasing_value=("${${(@On)combined}#*$'\0'}")
keys_of_the_top_two_values=("${(@)keys_sorted_by_decreasing_value[1,2]}")

EDIT by @sch: the first 4 lines can be simplified to

combined=()
for k v ("${(@kv)A}") combined+=($k$'\0'$v)

The variables keys and values contain the keys and values of A in an arbitrary but consistent order. You can write keys=(${(k)A}) if there are no empty keys, and similarly for values. keys_sorted_by_decreasing_value sorts keys lexicographically, add the n flag to sort numerically (9 before 10) and remove O if you want to sort in increasing order (in which case the top two values can be obtained with the subscript [-2,-1]).

Ksh93 has a way to sort the positional parameters only, with set -s; this also exists in zsh but not in bash 4.2. Assuming your values don't contain newlines or control characters that sort before newlines:

keys=("${!A[@]}")
combined=()
for ((i=0; i <= ${#keys}; i++)); do combined[i]=(${A[${keys[$i]}]}$'\n'${keys[$i]}); done
set -A sorted -s "${combined[@]}"
top_combined=${sorted[${#sorted[@]}-1]}  # -2 for the next-to-largest, etc.
top_key=${top_combined#*$'\n'}

This is all pretty complex, so you might as well go for the external sort, which is a lot easier to write. Assuming that neither keys nor values contain control characters, in ksh or bash:

IFS=$'\n'; set -f
keys_sorted_by_decreasing_value=($(
    for k in "${!A[@]}"; do printf '%s\t%s\n' "${A[$k]}" "$k"; done |
    sort | sed $'s/\t.*//'
  ))

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The ideal way is creating a soft link directory called adt, and re-creating it after SDK changes.

Thus, your PATH will stay the same.

Best Answer

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