awk : Need Help in Understanding a command Post: 302954831

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Top Forums Shell Programming and Scripting awk : Need Help in Understanding a command Post 302954831 by cjcox on Friday 11th of September 2015 11:37:54 AM

09-11-2015

Registered User

So... I get the idea that "float_test" is passed an awk expression.

so what happens (I think this is poorly written)...

1. echo - programmer wanted to use awk's expression evaluator but didn't use /dev/null which is probably better (?)

2. awk doesn't add a line with END, it just performs something at the end of stream of data (in this case "echo", but again probably could have used /dev/null.

3. The "$1" comes from the shell, in the case the argument passed to float_test where is will become a piece of awk text to be processed.

Since you place inline awk in single quotes he's breaking out the single quotes to insert the shell variable "$1". This is how you did things a long time ago or you could say this is how you do things now to be portable across different vendor version OS levels of awk like things.

So it's called "float_test", but you could use this for just about anything. Might be interesting to see how float_test gets called in the script.

Try:

Code:

float_test a=1
echo $?

float_test whatever-really-just-type-whatever
echo $?

but the following also works

Code:

float_test not-a-number
echo $?

float_test 3.14
echo $?

Which is probably close to how it's used in context

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LEARN ABOUT LINUX

igawk

IGAWK(1)							 Utility Commands							  IGAWK(1)

NAME

       igawk - gawk with include files

SYNOPSIS

       igawk [ all gawk options ] -f program-file [ -- ] file ...
       igawk [ all gawk options ] [ -- ] program-text file ...

DESCRIPTION

       Igawk is a simple shell script that adds the ability to have ``include files'' to gawk(1).

       AWK programs for igawk are the same as for gawk, except that, in addition, you may have lines like

	      @include getopt.awk

       in your program to include the file getopt.awk from either the current directory or one of the other directories in the search path.

OPTIONS

       See gawk(1) for a full description of the AWK language and the options that gawk supports.

EXAMPLES

       cat << EOF > test.awk
       @include getopt.awk

       BEGIN {
	    while (getopt(ARGC, ARGV, "am:q") != -1)
		 ...
       }
       EOF

       igawk -f test.awk

SEE ALSO

       gawk(1)

       Effective AWK Programming, Edition 1.0, published by the Free Software Foundation, 1995.

AUTHOR

       Arnold Robbins (arnold@skeeve.com).

Free Software Foundation					    Nov 3 1999								  IGAWK(1)

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