Question

#!/bin/bash
# This file will fix the cygwin vs linux paths and load programmer's notepad under windows.
# mail : <[e-mail]> 
# invokes the GNU GPL, all rights are granted.


# check first parameter is non empty.
# if empty then give a error message and exit.
file=${1:?"Usage: pn filename"};

if [[ "$file" == /*/* ]] ;then
  #if long directory name.
# :FAILTHROUGH:
  echo "$0: Executing pn.exe $file" 

else 
  file="$(pwd)/$file";
fi

#check whether the filename starts with / if so replace it with appropriate prefix #
prefix="C:/cygwin/";

#check for the partterns starting with "/" #
echo $var | grep "^/*$"
if [[ "$?" -eq "0" ]] ;then
  # check again whether parttern starts with /cygdrive/[a-z]/ parttern #
  if [[ $file == /cygdrive/[a-z]/* ]] ; then 
    file=${file#/cygdrive/[a-z]/};
    file="C:/"$file;
  else
    file="$prefix""$file";  
  fi 
fi


#check for the appropriate file permissions #
# :TODO: 


echo $file
exec "/cygdrive/c/Program Files (x86)/Programmer's Notepad/pn.exe"  $file 

as I in my program which convert path names between cygwin and windows and load
the pn.exe [ programmer’s notepad in windows]. So my questions are,

1. There are built in regex expression for the “[[” or ‘test’ operator. (as well as
   I used them in my above program). But why they don’t work in here if I change,

   echo $var | grep "^/*$"
   if [[ "$?" -eq "0" ]] ;then
   

   to this,

   if [[ "$file" == ^/*$ ]] ;then
   

   What is the reason for that? Is there any workaround?
   I have already tried the second method [[ "$file" == ^/*$ ]] but it didn’t work.
   then , simple googling brought to me here: http://unix.com/shell-programming

2. How to find all the documentation about [[ operator or ‘test’ command? I have used
   man test but :(. Which document specifies it’s limitations on regex usage if there so.

Answer 1

First, grep "^/*$" will only match paths containing only slashes, like “/”, “///”, “////”. You can use grep "^/" to match paths starting with a slash. If you want to use bash regexes:

var="/some"
#echo $var | grep "^/"
if [[ "$var" =~ ^/ ]] ;then
  echo "yes"
fi