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Top Forums UNIX for Dummies Questions & Answers Last word of lines Post 61026 by finster on Thursday 27th of January 2005 09:03:58 AM

01-27-2005

Registered User

From google:

awk's basic mode of operation is to read its input, chop each line into fields separated by some delimiter (white space by default, but you can change it), and then allow you to do pattern matching and other operations based on those fields. The thing I use it for most often is to grab a particular field.

Let's look at a trusty long ls listing:

--------------------------------------------------------------------------------

% ls -l
-rw-r--r-- 1 jeffy 28 May 9 16:12 Makefile
-rwxr-xr-x 1 jeffy 24576 May 28 11:31 foo
-rw-r--r-- 1 jeffy 57 May 9 16:13 foo.c
-rw-r--r-- 1 jeffy 57 May 28 11:37 foobar
-rw-r--r-- 1 jeffy 71 Jun 2 11:45 fumpty

--------------------------------------------------------------------------------
Suppose I want to grab just the file sizes for some reason. awk numbers fields starting with 1 (not zero like you'd expect from a bunch of unix geeks), so we count across and see that we want to print out field 4, so just do this:
--------------------------------------------------------------------------------

% ls -l | awk '{print $4}'
28
24576
57
57
71

--------------------------------------------------------------------------------
Easy as pie. Notice that the awk program is enclosed in single quotes. This protects the "$4" from the shell so it gets evaluated by awk, not csh (or whatever)
You can print out multiple columns in any order by separating them with commas:

--------------------------------------------------------------------------------

% ls -l | awk '{print $3, $1, $4, $NF}'
jeffy -rw-r--r-- 28 Makefile
jeffy -rwxr-xr-x 24576 foo
jeffy -rw-r--r-- 57 foo.c
jeffy -rw-r--r-- 57 foobar
jeffy -rw-r--r-- 71 fumpty

--------------------------------------------------------------------------------
Notice that the separating white space is not preserved, but gets scrunched down to a single space.
Wait a minute, what's with that "$NF" in that last example? NF is an internal awk variable that always represents the Number of Fields in the current line. By sticking a dollar sign in front of it, I get the equivalent of a "$8" when I run the script on the "ls -l" output. But I don't have to know how many fields there are, I can just grab the last one.

-Thanks .--from your question - it made me learn "awk"!!

finster

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LEARN ABOUT DEBIAN

cdbsplit

COOKIETOOL(6)							   Games Manual 						     COOKIETOOL(6)

NAME

       cdbsplit - program to operate cookie (fortune) database

SYNOPSIS

       cdbsplit [options] <cookie-database> <hitfile>

DESCRIPTION

       This manual page documents briefly the cdbsplit command.

       This  manual  page  was written for the Debian GNU/Linux distribution because the original program does not have a manual page. Instead, it
       has some plain text documentation, see below.

       cdbsplit is a program that can be used to operate cookie database in various formats, the default is standard fortune(6) format, i.e.  list
       of  'cookies'  delimited with line containing a single percent ('%') char . With 'cdbsplit' you can split cookie database, or extract parts
       of it depending on various criteria.

OPTIONS

       A summary of options is included below. For a complete description, see the documentation in  /usr/share/doc/cookietool	directory.   NOTE,
       that  default  behaviour  is  to  overwrite existing database with its reduced version, so the cookies are MOVED to hitfile. The hitfile is
       never overwritten, but may be appended to.

       [nothing]
	      Shows summary of options.

       -c     case-sensitive comparisons (for both keywords and groups)

       -d[0-3]
	      how fussy about word delimiters? (default: 2)

       -k<keyword>
	      optional keyword

       -K<keyword>
	      mandatory keyword (use both of them to form boolean expressions)

       -l<min_lines>
	      minimal cookie length (in lines)

       -L<max_lines>
	      maximal cookie length (in lines)

       -w<chars>
	      minimal line width (in chars)

       -W<chars>
	      maximal line width (in chars)

       -n<min_number>
	      start at cookie <min_number>

       -N<max_number>
	      stop after <max_number> cookie

       -m<chars>
	      find groups of cookies starting with <n> matching characters (database must be sorted for this to make sense!)

       -x     extract only, don't modify <cookie-database>

       -a     append, don't overwrite <hitfile> if such a filename exists

       -f[0-3]
	      input file format - -f3: cookies are separated by '%%' lines; -f2: cookies are separated by '%' lines (DEFAULT); -f1: each line is a
	      cookie; -f0: each word is a cookie.

SEE ALSO

       cookietool(6), cdbdiff(6)

BUGS

       None known.

AUTHOR

       Upstream  author  and  Aminet cookietool.lha package with AmigaOS binaries uploader is Wilhelm Noeker, <wnoeker@t-online.de>. Unix manpages
       (including this one) and makefile are maintained by Miros/law L. Baran <baran@debian.org>. This manual page uses  many  excerpts  from  the
       original README file.

								   May 19, 2001 						     COOKIETOOL(6)