basic awk questions Post: 302552103

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Top Forums Shell Programming and Scripting basic awk questions Post 302552103 by guessingo on Thursday 1st of September 2011 03:38:13 PM

09-01-2011

Registered User

Thank you for your help and the tip on the book. I'll check it out. I googled around and found some intro pages. I have used a link awk in my scripts such as print a certain tab, but that is it.

the c=0, through me off since I couldn't figure out why it was done. It looks like its unnecessary.

There still one part that is unclear to me.

Quote:

4. { i=1; while ( i <= NF )
This a loop. that runs until the end of the line.

5. { f=$i;
didn't they just set i=1, and then increment it.
if f=$i, shouldn't that be a number instead, it appears it is what is actually in that field?

-- your answer:
The script is iterating (in the while loop) over each of the fields in the input that you pass to your script.
So, $i the first time will refer to field 1 and $i the second time will refer to field 2 and so on - until NF, the total number of fields.

-GP

1. This is odd to me. It looks like, i is basically an index value in an array correct. So when I set i=1, this is short hand for go to the first index value of the array and the array is broken up by the spaces in my data file. Or should I look at $i as some kind of de-ref (old C terminology. had some C when I was an undergrad). so 'i' is basically a pointer. Awk syntax is a little different than what I am used to.

2. awk seems pretty useful for parsing files. I need to parse a sql output file. I was going to use the standard unix READ LINE, but I think awk will be easier (if I can figure out how to do it. ). The ability to pipe a unix function such as grep (to go line by line) into awk to go across the same line is very useful. Its look setting up a nested loop, but with simpler syntax.

for i in loop ...
for j in loop

thank you for your help. Your response was great. I was worried that this would be hard to follow.

guessingo

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LEARN ABOUT OPENSOLARIS

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).

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +--------------------+-----------------+
       |  ATTRIBUTE TYPE    | ATTRIBUTE VALUE |
       +--------------------+-----------------+
       |Availability	    | SUNWgawk	      |
       +--------------------+-----------------+
       |Interface Stability | Volatile	      |
       +--------------------+-----------------+
NOTES

       Source for gawk is available on http://opensolaris.org.

Free Software Foundation					    Nov 3 1999								  IGAWK(1)