Bash – shell scripts are still working without #!(sha-bang line)

bashshell-script

I am new to shell scripts and many books have written that use #!(sha-bang) line in starting of the script to invoke the interpreter .And this will invoke a new shell for script and do the interpretation line by line.But one of my basic script is still running without the magic line.

so my questions are:

from where did my basic script get the interpreter.
how did the script manages to locate the interpreter.

now let me tell you about my basic script it just contains the following line:

echo "basic script without the magic lines"

Best Answer

If the magic line is not provided, a default shell is used to run the script. This default shell could either be Bourne shell (sh) which is the case in some flavors, however, in some other flavors, the default shell used is same as login shell to execute it. The thing is: Don't leave it to the system to decide the shell, always provide the shell which you want in the first line.

Related Solutions

Bash – How to Name a File in the Deepest Level of a Directory Tree

That's an odd request!

I'd use find + awk to grab a file in the deepest directory:

bash-3.2$ deepest=$(find / -type f | awk -F'/' 'NF > depth {
>     depth = NF;
>     deepest = $0;
> }
>
> END {
>     print deepest;
> }')

Using ${deepest} in your mv command is left as an exercise but the following five lines may help you further:

bash-3.2$ echo "${deepest}"
/Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/vendor/tzinfo-0.3.12/tzinfo/definitions/America/Argentina/Buenos_Aires.rb

bash-3.2$ echo "${deepest%.*}"
/Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/vendor/tzinfo-0.3.12/tzinfo/definitions/America/Argentina/Buenos_Aires

bash-3.2$ echo "${deepest%/*}"
/Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/vendor/tzinfo-0.3.12/tzinfo/definitions/America/Argentina

bash-3.2$ echo "${deepest##*/}"
Buenos_Aires.rb

bash-3.2$ echo "${deepest##*.}"
rb

Following update to question:

find -type d [...] "This would only find the directory. [...] How could this be solved in the most simple way?".

By supplying -type f to find to find all files (f), not all directories (d).

Shell – Add text with echo but start with new line if file not empty

You can test to see if a file is empty by using unix test -s. Example below...

 if [ -s $file ]
then
   echo "File size is zero"
else
   echo "File size is not zero"
fi

Best Answer

Related Solutions

Bash – How to Name a File in the Deepest Level of a Directory Tree

Following update to question:

Shell – Add text with echo but start with new line if file not empty

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