OneAndOneIs2

Thu, Sep 15, 2011

Awesomeness!

• Post categories: Omni, FOSS, Technology, Programming

When you have multiple checkouts of a codebase, and work in multiple terminals, it's easy to suffer a momentary confusion about where you're executing a command, and break something important when you thought you were working in a safe place.

This is something I've been thinking about fixing for a while, but then two of my co-workers asked me to come up with something for this issue as well, so I finally got off my posterior and did something that (IMHO) is actually quite cool :)

So what I now have is a bash prompt that looks in your current directory, and also all parent directories, for a file named .ps1_alert and if it finds one (or more) it puts the alert in that file into your prompt, in bright red.

All you have to do is add \[\033[01;31m\]$(__ps1_alerts "(%s)")\[\033[00m\] to your bash prompt. This is easy:

$ echo $PS1

\n\u@\h:\W\$

$ export PS1='\n\u@\h:\W\[\033[01;31m\]$(__ps1_alerts "(%s)")\[\033[00m\]\$ '

$ echo $PS1

\n\u@\h:\W\[\033[01;31m\]$(__ps1_alerts "(%s)")\[\033[00m\]\$

This works instantly, but only for the current shell: Add the code to your PS1 in your .bashrc file to make it stick.

Then just save this perl script as /usr/bin/__ps1_alerts and the prompt will start to work:

#!/usr/bin/perl



use strict;

use warnings;



# Get the current directory

my $pwd = `pwd`;

chomp $pwd;



# Populate an array with the directory pathnames

my @dirs = split m#/#, $pwd;



# We only want the 'nearest' alert line, so declare it outside the loop

# and over-write it each time a new one is found

my $alert = '';



# Check for an alert file in each directory from root to current dir.

for my $i (0..$#dirs){

    my $wd = join "/", map $dirs[$_], 0..$i;

    my $alert_file = $wd.'/.ps1_alert';



    # If there's an alert file, grab the first line & output it

    if (-e $alert_file && -r $alert_file){

        open (my $file, "<$alert_file") or die "Can't open alert file\n";

        $alert = <$file>;

        chomp $alert;

        }

    };



# Output the alert:

print $alert;