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I've a sequence of commands to be used along with lot of pipings, something like this:

awk '{ if ($8 ~ "isad") {print $2, $5, "SE"} else {print $2, $5, "ANT"} }' "/var/log/apache2/other_vhosts_access.log" | grep -v '127.0.0.1' | tr '[' '\0' | tr [:lower:] [:upper:] | sort -t' ' -s -k3

This basically filters the Apache log and prints three cols of info. First col is IP address, second is time, third is a string. The output could be sorted based on any column so, I need to use '-m' with sort for the time field. Sorting order could also be reversed.

I want a string to store the arguments to sort, and let the combined strings get executed. Something like this:

$AWK_CMD | $SORT_CMD $SORT_KEY $SORT_REV

where

SORT_CMD="sort -t' '"
SORT_KEY="-k$1"      # $1 from cmd line arg
SORT_REV="$2"        # Either -r or blank

Am able to build such strings; when I echo it, it looks fine. Problem is, how to execute it? I get some errors like:

awk '{ if ($8 ~ "isad") {print $2, $5, "SE"} else {print $2, $5, "ANT"} }' "/var/log/apache2/other_vhosts_access.log" | grep -v '127.0.0.1' | tr '[' '\0' | tr [:lower:] [:upper:] | sort -t' ' -s -k3
Running ...
awk: '{
awk: ^ invalid char ''' in expression

Please ignore if 'sort' doesn't sort properly, that can be fixed. I wish to know how I can build the final command string in steps. The ways I tried to execute this command in the script is by:

$final_cmd
`$final_cmd`

Edit: The script that I'm trying to use

KEY=$1      # Values {1, 2, 3}
REVERSE=$2  # Values {0, 1} 

SORT_CMD="sort -t' ' -s"
SORT_KEY="-k$KEY"
if [[ $KEY -eq 2 ]]
then
    SORT_KEY="-m -k2"
fi

if [[ $REVERSE -eq 1 ]]
then
    SORT_REV="-r"
else
    SORT_REV=
fi

final_cmd="awk '{ if (\$8 ~ \"isad\") {print \$2, \$5, \"SE\"} else {print \$2, \$5, \"ANT\"} }' $LOG_FILE '|' grep -v '127.0.0.1' '|' tr '[' '\0' '|' tr [:lower:] [:upper:] '|' $SORT_CMD $SORT_KEY $SORT_REV"

echo $final_cmd
echo "Running ..."
$final_cmd
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2 Answers 2

up vote 3 down vote accepted

The different parts can be put in shell functions :

awkfilter() {
    awk '{ if ($8 ~ "isad") {print $2, $5, "SE"} else {print $2, $5, "ANT"} }' $1
}

toupper() {
    tr [:lower:] [:upper:]
}

dosort() {
    sort -t' ' -s -k3
}

awkfilter "/var/log/apache2/other_vhosts_access.log" | grep -v '127.0.0.1' | tr '[' '\0' | toupper | dosort

then you could make things optionnal more easily :

dosort() {
    rev=""
    if [ "$2" == "reverse" ]
    then
        rev='-r'
    fi
    sort -t' ' -s -k$1 $rev
}

When your command-line is starting to be really long, writing it in a script and breaking it in parts (with functions) is usually really helpfull.

share|improve this answer
    
Thanks, Fussy! I too was trying to achieve the same, however, with string concatenation. But I think you gave me a better option. :) –  Barun Feb 18 '11 at 13:02

When you run awk '{ ... }' on a shell prompt or from a shell script, shell parses the quotes and passes the argument to awk w/o the quotes. What happens is that you somehow run it with the quotes in parameter.

Edit: with your update to question, what you need is sh -c "$final_cmd".

share|improve this answer
    
Like alex says, somehow the quote stays on execution. Can you (Barun) post the contents of $final_cmd and how you got it set? –  asoundmove Feb 18 '11 at 12:31
    
Sure. I'm appending the script to my original post. –  Barun Feb 18 '11 at 12:47

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