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Re: trapped in bash

On 18/12/16 06:30 PM, Bart Schaefer wrote:
On Dec 19, 12:32am, Daniel Shahaf wrote:
} I suppose you could write a command_not_found_handler() function that
} tried to reverse engineer _why_ the command wasn't found - with the
} obvious limitations, e.g., race conditions between the library's
} execution and the handler's.

I don't think there can be a race here because the handler won't be
invoked if the execve() hasn't already failed.

Something like this:

command_not_found_handler () {
   local attempt="$1"
   if [[ "$1" != /* && ( -o pathdirs || "$1
" != */* ) ]]
     emulate zsh -c 'attempt=$^path/$1(N[1])'
   if [[ -f $attempt ]]
     local hashbang
     read -u 0 -k 2 hashbang < "$attempt"
     case "$hashbang" in
       ('#!') print -u2 -- $1\: bad '#!' interpreter ;;
       (*) print -u2 failed to load $1 ;;
     print -u2 -- $1\: no such file in \$PATH
   return 127

Not for me to say, but it seems to me that the simple fact that a file exists or does not exist is simple enough to determine in the tradition of 'whence' or something like that. *Then* we run into issues about executing it *after* the thing has (obviously) been found. Sometimes a command can't be found because it can't be found, that is, the file simply does not exist. Or is that too simple? Anyway I sure like the idea.

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