UNIX for Dummies Questions & Answers

is

Code:

!

also used for documentation/multi line comment purpose in unix shell scripting?

Not really, no.

Strange question. In your previous thread you were using ! as the terminator for Here Documents in Shell.

I believe ! is a comment in HTML and XML .

"
(Originally posted by methyl)
Problem was the two lines like this:

Code:
!
Because they were not in column 1, all the lines from the <<! to the next line which did properly start with ! were treated as part of the Here Document. Thus most of your code did not execute (and that includes the "elif" line)."

Yes methyl, As per you response only I felt that by using ! can be used for documentation purpose... does it means it need to have

Code:

<<!

&

Code:

!

?

Because usually whenever I write a code in shell I face this problem that few part of my code get documented and it lost control

If I understand you correctly. There is no multi-line documentation symbol in unix Shell (unlike some programming languages). Anything from a hash sign onwards on the same line is comment.

Code:

#The documentation sign in unix Shell script is a hash
# Like this
# And this
#
ls -lad    # This command produces a directory listing
#
# The next line produces a directory listing
ls -lad

By 'documentation purposes' do you mean for a here document?

In theory, you can use almost any string as the delimiter, but normally you'll see 'EOF' or 'EOD'. '!' would be a slightly odd choice though, as it's often a special shell character.

The important thing is that the delimiter string has to be the first thing on the line (with no preceding whitespace) in order to terminate the heredoc.

Good thinking CarloM.

I've seen ! used as the terminator for a Here Document in an old Shell Tutorial book. Maybe that is why it is so common.
As you say, most people prefer EOF or EOD . We have system scripts containing many variants - including ==end_of_command== .
I used to use **** because it was the standard terminator for a punched card reader.