A way to parse terminal output / input ? (.bashrc ?)

Question

Is there a way to parse input and output from bash commands in an interactive terminal before they reach the screen ? I was thinking maybe something in .bashrc, but I'm new to using bash.

For example:

• I type "ls /home/foo/bar/"
• That gets passed through a script that replaces all instances of 'bar' with 'eggs'
• "ls /home/foo/eggs/" gets executed
• The output gets sent back to the replace script
• The output of the script is sent to the screen

Answer 1

Yes. Here's something I wrote for my own use, to wrap old command line Fortran programs that ask for file-paths. It allows escaping back to the shell for e.g. running 'ls'. This only works one way, i.e. intercepts user-input and then passes it on to a program, but gets you most of what you want. You can adapt it to your needs.

#!/usr/bin/perl

# shwrap.pl - Wrap any process for convenient escape to the shell.
# ire_and_curses, September 2006

use strict;
use warnings;


# Check args
my $executable = shift || die "Usage: shwrap.pl executable";

my @escape_chars = ('#');                    # Escape to shell with these chars
my $exit = 'exit';                           # Exit string for quick termination

open my $exe_fh, "|$executable @ARGV" or die "Cannot pipe to program $executable: $!";

# Set magic buffer autoflush on...
select((select($exe_fh), $| = 1)[0]);

# Accept input until the child process terminates or is terminated...
while ( 1 ) {
   chomp(my $input = <STDIN>);

   # End if we receive the special exit string...   
   if ( $input =~ m/$exit/ ) {
      close $exe_fh;
      print "$0: Terminated child process...\n";
      exit;            
   }

   foreach my $char ( @escape_chars ) {   
      # Escape to the shell if the input starts with an escape character...
      if ( my ($command) = $input =~ m/^$char(.*)/ ) {
         system $command;
      }
      # Otherwise pass the input on to the executable...
      else {
         print $exe_fh "$input\n";
      }
   }
}