Bash – Command not found running in shell script

If the script properly begins with #!/bin/bash (you can't have another comment before that), you should simply execute it by typing /path/to/script.sh, without that . at the beginning. The . is an include statement, it means “execute the contents of this file as if it had been typed here on the command line” (this is called “sourcing” in unix shell jargon).

Running bash and sourcing the script should work. I'm guessing that because you had bash automatically started in some circumstances, but you prefer zsh, you've set up bash to automatically switch over to zsh — maybe with exec zsh in your ~/.bashrc. Don't do that: instead you should switch over to zsh in the file that's executed when you log in, i.e. ~/.profile, and leave .bashrc alone. To have zsh be executed in terminals, set the SHELL environment variable:

# in ~/.profile
export SHELL=/bin/zsh
if [ -t 1 ]; then exec $SHELL; fi

It's unfortunate that you can't modify the script, because it's buggy. The brackets should be quoted, even in bash. If there is a file called 3+ in the current directory, the call to egrep will search for one or more occurrences of the digit 3 instead of a sequence of arbitrary digits. If there is a file called 3+ and a file called 4+, the call to egrep will search for 3s in the file 4+. Here, the difference between bash and zsh only comes into play when no file matches the supplied pattern: bash silently runs the command with the unsubstituted pattern, whereas zsh signals an error (by default).

After snooping around various forums and some Stack-overflow post I found the issue.

Here is an explanation to better understand and 'see' the root cause of the errors.

First off if you are writing code on Windows, better arm yourself with Notepad++. It's basically the Swiss Army knife of text-editors in my opinion.

Now to have a look at the EOL (end-of-line) characters and other control symbols do the following:

1.Open the file in Notepad++.

Select View > Show Symbol > Show All Characters from the Menu bar

You should now see the symbols as follows:

Aha! Windows/MS-DOS uses CR+LF to indicate end-of-lines. Now UNIX uses LF character to indicate line termination (EOL character).

2.1.Let's convert the Windows EOL into UNIX EOLs:

Select EDIT > EOL Conversion > UNIX Format

You should see something like this:

This explains why we saw the '\r' character getting appended at the end of the line. This is because UNIX recognized the '\n' or LF (linefeed) as the line termination/EOL character but ignore the '\r' or ^M (carriage return) character.

We can also test for the EOL issue by

bash-3.00$ head myScript.sh | cat -vet | head -1
#usr/bin/bash^M$
bash-3.00$ #We see that ^M, that is \r is found at the end of each line. 

2.2.If you would like convert the file from Windows to UNIX EOL format on UNIX then there are two ways of fixing this:

$ dos2unix myScript.sh

or

Use the solution provided by @Chris Down as below:

$ sed -i 's/\r$//' myScript.sh

References:

1. For more information on line termination and what-is-the-difference-between-r-and-n refer these links.