Shell Programming and Scripting

<aaa bbb="xxxx" params="@abc@ @defghi@ @j@"></aaa>
<aaa params="@abc@ @defghi@">value</aaa><aaa params="@klm@ @nopq@ @rstu@"></aaa>
<aaa params="@v@ @wxy@ @z@"></aaa>

params="@a@ @b@ @c"

param1="@a@" param2="@b@" param3="@c@"

awk '/params/{gsub(" @","\" params=\"",$0);i=1;do{sub("params","param"(i),$0);i++}while(match($0,/params/))}1' infile

[ctsgnb@shell ~/sand]$ cat tst
<aaa bbb="xxxx" params="@abc@ @defghi@ @j@"></aaa>
<aaa params="@abc@ @defghi@">value</aaa><aaa params="@klm@ @nopq@ @rstu@"></aaa>
<aaa params="@v@ @wxy@ @z@"></aaa>

[ctsgnb@shell ~/sand]$ awk '/params/{gsub(" @","\" params=\"@",$0);i=1;do{sub("params","param"(i),$0);i++}while(match($0,/params/))}1' tst
<aaa bbb="xxxx" param1="@abc@" param2="@defghi@" param3="@j@"></aaa>
<aaa param1="@abc@" param2="@defghi@">value</aaa><aaa param3="@klm@" param4="@nopq@" param5="@rstu@"></aaa>
<aaa param1="@v@" param2="@wxy@" param3="@z@"></aaa>
[ctsgnb@shell ~/sand]$

# nawk '{while(/params/){match($0,/<aaa[^>]*params[^>]*>/);x=substr($0,RSTART,RLENGTH);y=x;gsub(" @","\" params=\"@",x);do{sub("params","param"(++i),x)}while(match(x,/params/));sub(y,x,$0);i=0}}1' tst
<aaa bbb="xxxx" param1="@abc@" param2="@defghi@" param3="@j@"></aaa>
<aaa param1="@abc@" param2="@defghi@">value</aaa><aaa param1="@klm@" param2="@nopq@" param3="@rstu@"></aaa>
<aaa param1="@v@" param2="@wxy@" param3="@z@"></aaa>

echo "<aaa bbb="xxxx" params="@abc@ @defghi@ @j@"></aaa>
<aaa params="@abc@ @defghi@">value</aaa><aaa params="@klm@ @nopq@ @rstu@"></aaa>
<aaa params="@v@ @wxy@ @z@"></aaa>" |
gawk '{gsub(/params=|\"/,"")}
{for(i=1;i<=NF;i++) {if($i~/@/) if($i~/aaa/){$i="params="++x"\""gensub(/>/,"\">",1,$i)} else {$i= "params="++x"\""$i"\""};if($i~/aaa/)x=0}}1'
<aaa bbb=xxxx params=1"@abc@" params=2"@defghi@" params=3"@j@"></aaa>
<aaa params=1"@abc@" params=2"@defghi@">value</aaa><aaa params=1"@klm@" params=2"@nopq@" params=3"@rstu@"></aaa>
<aaa params=1"@v@" params=2"@wxy@" params=3"@z@"></aaa>