Very Computer

Quote:>files=`ls -rt * |grep -v '.*[a-zA-Z].*' | awk $1 '>=' $zots {print}`

--

          A mountain is something you don't wanna * with.

        Argh, forgot one '

Quote:>files=`ls -rt | grep -v '.*[a-zA-Z].*' | awk '$1 >= '$zots' {print}`

          A mountain is something you don't wanna * with.

        i have a simple little shell question.  I am attempting
to write a script that will perform various manipulations on news
articles.  my problem seems to be with understanding variable
substitution in sh.  a minimal example is the enclosed sh script.  what
it should do is set the variable files to be the names of those
articles in comp.std.c whose name (article number) is greater than or
equal to the numeric value of the scripts first argument.  this does
not behave as expected.  i have tried quite a unmber of variations on
this theme (mostly centering around multiple $'s and interesting
quoting of commands, but i tend to get all of the files or none of them
depending on (for some reason) the number of $'s preceding the zots
variable name (also on  the number in front of the 1, $1 or $$1, etc.
but i expected that ...) this is running under sunos4.1 if that is
interesting.  i have tried to read the manual, but with little
success.  anyone interested in pointing out my clear stupidity
publicly?  i *would* appreciate it ....

        many thanks ...

#!/bin/sh
cd /usr/spool/news/comp/std/c
zots=$1
echo "Should ignore files with name < $zots"
files=`ls -rt * |grep -v '.*[a-zA-Z].*' | awk $1 '>=' $zots {print}`
echo $files

--
Fred Whiteside   Chedoke-McMaster Hospitals, Hamilton, Ontario, Canada

Quote:>files=`ls -rt * |grep -v '.*[a-zA-Z].*' | awk $1 '>=' $zots {print}`

files=`ls -rt * |grep -v '.*[a-zA-Z].*' | awk "\$1 >= $zots {print}"`

Or, to make it a little more simpler... (You don't need .*'s in the grep)

files=`ls -rt * |grep -v '[a-zA-Z]' | awk "\$1 >= $zots {print}"`

To explain:

The only real change was to change thw quoting around the awk script.
$1 was getting expanded to the shell's $1, not the 1st awk field.

By using " as a quoting character, the shell is able to expand $zot to whatever
number it represents.  The \$1 is to prevent the shell from trying to expand $1
to the shell's $1, rather than the 1st awk field.

After the shell is finished with variable substitution,

awk "\$1 >= $zots {print}"

is transformed, and awk see's:  (if zot = 10)

awk "$1 >= 10 {print}"

Hope this helps!  A decent book on shell programming and quoting is the Howard
Sam's book on shell programming.

        -Jeff
--

Utek Engineering, Tektronix Inc.        +1 503 685 2568
                        SPEEA - Just say no.

On 30 Aug 90 00:56:38 GMT,

Quote:> #!/bin/sh
> cd /usr/spool/news/comp/std/c
> zots=$1
> echo "Should ignore files with name < $zots"
> files=`ls -rt * |grep -v '.*[a-zA-Z].*' | awk $1 '>=' $zots {print}`
> echo $files

Awk expects its program to be one argument. You've given it four. You DON'T
want the $1 to be expanded, but you DO want the $zots to be expanded, hence
the funny quoting.

James
--

DEC Western Software Lab., Palo Alto, California.         .....!decwrl!brister

a=123456
b=123

c=`expr $a - $b`

d=`expr $a \* $b`

echo "c = $c"
echo "d = $d"

Note, that the '*' MUST be quoted, as the shell will expand it.

"Shell qouting --  Know it, live it, be it.  -Jeff"    :-)

        -Jeff
--

Utek Engineering, Tektronix Inc.        +1 503 685 2568
                        SPEEA - Just say no.

Quote:>:>files=`ls -rt * |grep -v '.*[a-zA-Z].*' | awk $1 '>=' $zots {print}`
>I see a quoting problem here     ^^^^^^^^^^^^^^^^^^^^^
>files=`ls -rt * |grep -v '[a-zA-Z]' | awk "\$1 >= $zots {print}"`
>To explain:
> The only real change was to change thw quoting around the awk script.
>$1 was getting expanded to the shell's $1, not the 1st awk field.
>   By using " as a quoting character, the shell is able to expand $zot
>to whatever number it represents.  The \$1 is to prevent the shell
>from trying to expand $1 to the shell's $1, rather than the 1st awk
>field.

I have only been able to get awk to work properly if I use
single quotes and not double quotes.

As a side question, does ANYONE have any bourne shell routines which do
math... reasonably effeciently?  (For numbers > 1000?)
--
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 After he pushed me off the cliff, he asked me, as I fell, ``Why'd you jump?''

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If your system has named pipes - fifos - and bc then you may find this
useful:

#
# these instructions illustrate how to set up a background
# engine in a shell script - a simple application is shown only
# for illustration purposes - it numbers lines of standard input

# first allocate fifos

ITMP=/usr/tmp/i.$LOGNAME
OTMP=/usr/tmp/o.$LOGNAME

/bin/rm -f $ITMP $OTMP 2>/dev/null
/etc/mknod $ITMP p  # input fifo for engine
/etc/mknod $OTMP p  # output fifo for engine

# start background engine and open $ITMP as file descriptor 3
# and $OTMP as file descriptor 4

bc <$ITMP >$OTMP &
exec 3>$ITMP
exec 4<$OTMP

# send command to background engine
# if background engine is bc,  counters can be maintained
# echo "x = 1"
# echo "x = x + 1" or echo "++x"
#the second version returns the new value of x

echo "x = 0" >&3

while line=`line`
        do
        echo "x++" >&3
        # read response
        read ans <&4
        echo "$ans: $line"
        done < engine

# terminate background engine and remove fifos

echo "quit" >&3
/bin/rm -f $ITMP $OTMP

exit 0
--

Dan Mercer

"MAN - the only one word oxymoron in the English Language"

In general, I find that complex shell quoting is best solved with an
inside-out approach, get the inside to work and then add the next
level of quotes to that - of course, as you get better you need to
do less and less of this - Neil
--
========================================================================
Neil Smithline

UUCP:    ..!rutgers!rochester!smithln

    awk '$1 >= '$zots' {print}'

it will work, because the "$1" is quoted for awk's sake, and all white
space is quoted to prevent the shell from passing 4 strings, not 1, to
awk as arguments.  Note that we step out of the quotes long enough to
let the shell substitute for "$zots".

ADVANCED DISCUSSION:

One might think you could use double quotes around the whole awk program,
and just escape the "$1" but not "$zots", thus:

    awk "\$1 >= $zots {print}"

and indeed this would work if it were not for the fact that the entire
pipeline is enclosed in backquotes.  A peculiarity of backquoting is
that it forces an extra level of evaluation, so "\$1" is no safer than
"$1".  You must use

    awk "\\$1 >= $zots {print}"

to get this to work.

Another subtlety: if your program were not doing a numeric comparison,
you'd have to arrange for "$zots" to be presented to awk as a string.
My first example would become something like

    awk '$1 == "'$zots'" {print}'

and the second,

    awk "\\$1 == \"$zots\" {print}"

- Eddie sez: ----------------------------------------------- (c) 1986, 1990 -.
|   {o >o                                                                     |
|    \ -) "I was an infinitely hot and dense dot."                            |

I'm surprised no one mentioned the simple way:

        awk '$1 >= MAX{print}' MAX=$zots -

The MAX=value sets the awk variable MAX to 'value', the dash is needed
to indicate using stdin.  You could eliminate the grep by letting awk
do it for you:

        awk '/^[0-9]*/{if ($1 >= MAX) print}' MAX=$zots -

No that we have probably confused the original poster beyond hope ...

Good luck!
Bill Pringle

The nice thing about Unix is that there are so many right answers!

=========
/*
 *      Count.c
 *
 *      print succesive numbers from start to end.
 *      Used in scripts instead of `expr $i +1`
 */
#include <stdio.h>
main(argc,argv)
int argc; char *argv[];
{
register int i,j;
i=atoi(argv[1]);
j=atoi(argv[2]);
while (i <= j)
        printf(" %d",i++);

Quote:}

Quote:>#include <stdio.h>
>int argc; char *argv[];
>while (i <= j)
> printf(" %d",i++);

This next routine isn't supposed to be sophisticated... but it works--
just give it two SMALL NUMBERS.

ADDITION ()
 {
  NUM1="$1"
  NUM2="$2"
  shift $#
  while test $# -lt $NUM1
  do

  done

  shift $#
  while test $# -lt $NUM2
  do

  done

  set - $NUM1 $NUM2
  TOTAL=$#
 }

I am working on a sort of LIBRARY of SHroutines where all I have to do is
include the clode  ``. COUNT'' for the next... and use the code.

COUNT ()
 {
  test $# = 0 &&\
   {
    echo "$0: Usage: $0 value [...]"
    exit 1
   } ||\
    {
     for i
      {
       set ""
       while :
       do
         set $* " x"
         echo $#
         if test $# = $i; then
           break
         fi
       done
     }
    }
 }

Of course, ``COUNT x'' is a great counter!  :-)

The main problem with the two loops is the ``set " $*"'' command.
This is what takes so much time when the argument list grows.

--
Signature follows. [Skip now]

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

 After he pushed me off the cliff, he asked me, as I fell, ``Why'd you jump?''

 ODU/UNIX/BSD/X/C/ROOT/XANTH/CS/VSVN/
 -----------------------------------------------------------------------------