Summary: Shell Question

Thanks to this great list...
I can not imagine the response, This is an excellent list. which helped me
solve my shell problem.

The Question was:
      I want to parse some variable from shell to awk ( without using
export ).
for ex.  if $1 & $2 are 2 arg's, then i want to use it in awk statement
like

awk '{ if ( ($SHELL_Variable1 < $1) && ($SHELL_Variable2 > $2) ) print
"something" }'

I tried with $ ' "${ SHELL_Variable1} " ' in all of the above forms; but
its not working.
- * -- * --- * -----
Many Thanks to the following experts for their nice Answers:

Andrew J. Caines
Johan Hartzenberg
Matthew Hannigan
Fabrice Guerini
Lumpkin, Buddy
Eric van de Meerakker
Kacem El Kassemi
Martin
Steudten Thomas
elline
Glass, David (UDB)
Hindley Nick
Wanke Matthias
Claude Charest
Reggie Beavers

;most of them pointed out the quoting problem & also suggested to using
awk/perl.
;Here are some of the Excellent explanations:
-----------------------------------
Andrew J. Caines Wrote:

> I want to parse some variable from shell to awk ( without using export ).

Exporting only affects the scope of the variables within shell
subprocesses and is not relevant to programs which manage their own
variables.

This is a simple issue of quoting. Singles quotes - '' - protect
everything in them from shell expansion and special character handling and
double quotes - "" - protect everything in them from special character
handling but allow shell expansion (at least in simple terms).

So if your shell has $1 and $2 defined and you want to use them in an
in-line awk script, then you simply don't protect them from the shell, eg.

# awk '{ if ( ('$1' < $1) && '$2' > $2) ) print "something" }'
      ----------  ------------  ------------------------------

The underlined sections are protected (ie. quoted), the rest is not and is
therefore liable to shell expansion.

You could also use double quotes and escape special characters, eg.
something like..

# awk "{ if ( ($1' < \$1) && $2 > \$2) ) print \"something\" }"

If you were actually trying to do a simple numerical comparison like the
example, then you should use the shell's built-in test command, ie.

# [ $1 -lt $abc1 -a $2 -gt $abc2 ] && echo "something"

..where you are populating $abc1 and $abc2 accordingly.


See "Quoting" section of sh(1) and ksh(1) and test(1).
---------------------------------------
Fabrice Guerini:

$ min=6; max=100
$ cat > /tmp/x
1 2
5 7
12 7
762 1
63 76
19 276
0 5
992 2
8 43
$ awk '{ if (('$min' < $1) && ($2 < '$max')) { print $0 } }' /tmp/x
12 7
762 1
63 76
992 2
8 43

Cheers!
---------------------------
Matthew Hannigan:
      It's painful isn't it!  I'd suggest you use perl instead, which
      is supplied with Solaris these days but here is your answer:
      end the quotes and restart them just after the variable:

                               awk  '{  if (('$SHELL_Variable1' < $1) &&
                               ('$SHELL_Variable2' > $2))
                                    print  "something"  }'

      or, just in case the shell variable results have spaces in them, use
      double quotes as well:

                               awk  '{  if (('"$SHELL_Variable1"' < $1) &&
                               ('"$SHELL_Variable2"' > $2))
                                    print  "something"  }'
---------------------------------
Eric van de Meerakker :

It isn't working because the awk script itself is between single
quotes (as it must be, or you won't be able to use the awk variables
$1, $2, etc.), which prevents the substition of shell variables in the
awk script text.

The solution to your problem is to the -v option of /usr/xpg4/bin/awk
or nawk, as follows:

nawk  -v SHELL_Variable1=$1 SHELL_Variable2=$2 '{  \
 if  ( (SHELL_Variable1 < $1) && (SHELL_Variable2 > $2) )
  print  "something"
}'

The -v option isn't availiable in /usr/bin/awk, but it will work for
/usr/xpg4/bin/awk and /usr/bin/nawk (xpg4/bin/nawk and nawk are
implementations of 'New' AWK, which has more features than 'classic'
AWK, but also a few differences); see the man pages for awk and nawk.
------------------------------------
Hi,
to the shell variables you have to quote them in 2 manners:
   '$var' (single quotes) or   4"$var"4  (one single quote + a double
quote)
ex.
umask and SHLVL are 2 shell variables
#!/bin/sh
var1=25
var2=5
 awk 'BEGIN { { if (('$umask' < '$var1' ) && ('"$SHLVL"' < '$var2')) \
    {print "something " '$umask'" " '"$SHLVL"'} else {print "not ok"} };
exit }'

Kacem El Kassemi
------------------------------------------

Your Support is Apreciated.

Thanks,
Abh,
- - - - - - - - - - - - - - -
Unix Administrator,KSA.
Cell +96657255468
------
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